Digitized by the Internet Archive in 2011 with funding from The Library of Congress http://www.archive.org/details/psychologyintrod02ange PSYCHOLOGY AN INTRODUCTORY STUDY OF THE STRUCTURE AND FUNCTION OF HUMAN CONSCIOUSNESS BY JAMES ROWLAND i^NGELL Head of the Department of Psychology tn the University of Chicago FOURTH EDITION, REVISED NEW YORK HENRY HOLT AND COMPANY Copyright, 1904, 1908, BY HENRY HOLT AND COMPANY s^ PREFACE TO THE FIRST EDITION /7f Psychologists have hitherto devoted the larger part of , their energy to investigating the structure of the mind. Of m late, however, there has heen manifest a disposition to deal more fully with its functional and genetic phases. To deter- mine how consciousness develops and how it operates is felt to be quite as important as the discovery of its constituent ele- ments. This hook attempts to set forth in an elementary way the generally accepted facts and principles bearing upon these adjacent fields of psychological inquiry, so far as they pertain to the mind of man. Inasmuch as it is mental activity, rather than mental structure, which has immediate significance for thought and. conduct, it is hoped that students of philosophy, as well as students of education, may find the book especially useful.* The author has had the interests of such students constantly in mind. The differing conditions under which introductory courses in psychology are- offered at various institutions render it desirable that a text-book should be adaptable to more than one set of circumstances. The present text has accordingly been arranged with the purpose of permitting considerable ■ flexibility in the emphasis laid upon the several portions of the subject. This fact accounts for an amount of repetition and cross-reference which otherwise would have been regarded as unnecessary. To my teachers. Professor John Dewey and Professor Wil- liam James, I owe much of what may be found good in these pages. Were not the list too long to recount, I should gladly express my obligations to the many other psychologists by whom I have been influenced in the formation of my viewB. iii Jiv PREFACE I am much indebted for advice and suggestion to a number of my colleagues in the University of Chicago, especially to Professor H. H. Donaldson, Professor A. W. Moore, and Dr. J. B Watson. My vs^ife has given me great assistance in the preparation of my manuscript. For the use of a number of illustrations acknowledgments are due to the following authors and publishers : William James; D. Appleton & Co., publishers of Barker's "The Nervous System"; W. B. Saunders & Co., publishers of "The American Text-Book of Physiology"; Walter Scott, Ltd., publishers of Donaldson's "Growth of the Brain"; John Murray, publisher of McKendrick and Snodgrass' "Physi- ology of the Sense Organs"; and G. P. Putnam's Sons, pub- lishers of Loeb's "Physiology of the Brain.'* J. E. A. University of Chicago, November, 1904. PREFACE TO THE FOURTH EDITION The present edition contains a large amount of new material, chiefly empirical in character. To offset this addi- tion, many of the more strictly theoretical discussions have been condensed. Most of the new matter is so introduced that it may be omitted if necessary without seriously impairing the exposition of general principles and theory. The old ma- terial has been re-arranged, many new drawings have been supplied, the paragraph headings have been elaborated, a list of collateral reading has been added at the close of the text, and at every point an earnest effort has been made to secure greater lucidity. Although there are occasional changes in the form of ex-" pression, there are no conscious alterations of the fundamental principles formulated in the earlier editions. For example, the presentations of imagery and volition have been somewhat modified in the interests of cogency, but the essential doctrines remain. After careful consideration I have refrained from adding a set of practical exercises for students, despite many re- quests for such material. I am convinced that a competent teacher can with advantage devise a group appropriate to his own peculiar needs. If time be lacking for arranging such a set, there are now available several good store-houses from which supplies can be drawn, not to mention the special manuals which are beginning to appear to meet just this need. It is a pleasure to acknowledge my obligation to many teachers in all parts of the country, to whose appreciative and intelligent criticism is due no small number of the vi PREFACE alterations incorporated in this edition. The real merits and defects of a text-book can only be adequately recognized in the actual stress of class-room, use, I am therefore particularly grateful for the suggestions made by instructors working under conditions somewhat different from those out of which this book originally grew. To my colleague, Dr. John B. Watson, to Professor Henry H. Donaldson of the Wistar Institute, and to Professor Arthur H. Pierce of Smith College, I am under an especial debt of gratitude for wise advice and helpful criticism. Acknowledgments are also due to the following authors and publishers for their kind permission to make use of illus- trations from their works: Professor W. H. Howell and W. B. Saunders & Co., publishers of his "Text-Book of Physi- ology"; Professors T. Hough and W. T, Sedgwick, and Ginn & Co., publishers of their "Elements of Physiology." J. E. A. University of Chicago, January, 1908. CONTENTS CHAPTER I PAGE The Problems and Methods of Psychology . . 1 CHAPTEE II The Psychophysical Organism and the Nervous System . 13 CHAPTER III Mind, Neural Action and Habit 59 CHAPTER IV Attention, Discrimination, and Association . . 80 CHAPTER V Sensation 109 CHAPTER VI Perception 151 CHAPTER VII The Perception of Spatial and Temporal Rela- tions 173 CHAPTER VIII Imagination 196 vii Viii CONTENTS CHAPTEE IX PAGE Memory 222 CHAPTEE X The Consciousness of Meaning and the Eokma- TiON OF Concepts 245 CHAPTEE XI Judgment and the Elements of Eeasoning . . 267 CHAPTEE XII The Forms and Functions of Eeasoning .... 279 CHAPTEE XIII The Affective Elements of Consciousness . . . 301 CHAPTEE XIV Feeling and the General Principles of Affective Consciousness . 316 CHAPTEE XV Eeflex Action and Instinct 334 CHAPTEE XVI The Important Human Instincts 346 CHAPTEE XVII Nature of Impulse 363 CHAPTEE XVIII The Nature of Emotion , , , 369 CONTENTS ix CHAPTEE XIX PAGE General Theory of Emotion 380 CHAPTEE XX Elementary Features of Volition 396 CHAPTEE XXI Eelation of Volition to Interest, Effort, and Desire 419 CHAPTEE XXII Character and the Will 434 CHAPTEE XXIII The Self . 440 Collateral Eeadings 459 Index . 465 PSYCHOLOGY CHAPTEE I PEOBLEMS AND METHODS OF PSYCHOLOGY Definition of Psychology. — Psychology is commonly de- fined as the science of consciousness. It is the business of a science systematically to describe and explain the phenom- ena with which it is engaged. Chemistry, physics, and the various branches of biology all attempt to deal in this man- ner with some special portion of the facts or processes of nature. Mental facts, or facts of consciousness, constitute the field of psychology. The Nature of Consciousness. — Consciousness we can only define in terms of itself. Sensations, ideas, pains, pleasures, acts of memory, imagination, and will — ^these may serve to illustrate the experiences we mean to indicate by the term; and our best endeavour to construct a successful definition results in some such list, of which we can only say: "These taken together are what I mean by consciousness." A psychological treatise is really an attempt to furnish the essentials for such a catalogue. It is generally maintained that despite our difiiculty in framing a satisfactory definition of consciousness, we can at least detect one or two of its radical differences from the physical objects which make up the rest of our cosmos. 2 PSYCHOLOGY These latter always possess position and extension, i. e., they occupy space. Psychical facts, or events, never do; on the other hand they possess one characteristic which, so far as we know, is wholly wanting to physical facts, in that they exist for themselves. A man not only has sensations and ideas, he knows that he has them. A stone or other physical object has no such knowledge of its own existence or of its own experiences. Yet, whatever may be the value of these distinctions, we need entertain no real fear of encountering any serious misapprehension of the inner nature of conscious- ness, for each one of us experiences it every day for himself and each is thus fitted to discuss it with some measure of accuracy. Former Definitions of Psychology. — Formerly psychology was often defined as the science of the soul. But the word soul generally implies something above and beyond the thoughts and feelings of which we are immediately conscious; and as it is these latter phenomena with which psychology is primarily engaged, this definition is now rarely used by care- ful writers. Psychology is also defined at times as the science of mind. The objection to this definition is that the word mind ordinarily implies a certain continuity, unity, and personality, which is, indeed, characteristic of normal human beings; but which may, for all we can see, be wholly lacking in certain unusual psychical experiences like those of in- sanity, or those of dream states, and may be wanting at times in animals. All consciousness everywhere, normal or abnor- mal, human or animal, is the subject matter which the psychologist attempts to describe and explain; and no defini- tion of his science is wholly acceptable which designates more or less than just this. Nevertheless, we shall often employ the term mind in this book, using it to designate the entirety of the intelligent processes which occur in the organism. The Procedure of the Psychologist. — In his description of conscious processes the psychologist attempts to point out the PROBLEMS OF PSYCHOLOGY 3 characteristic features of each distinguishable group of facts and of each member of such groups, and to show how they differ from one another. Thus, for example, the general group known as "sensations" would be described and marked off from the group knowji as "ideas"; and the peculiarities of each form of sensation, such as the visual and tactile forms, would be described and distinguished from one another and from those belonging to the auditory form. The psychologist's explanations consist chiefly in showing (1) how complex psychical conditions are made up of simpler ones, (2) how the various psychical groups which he has analysed grow and develop, and finally (3a) how these various conscious pro- cesses are connected with physiological activities, and (3b) with objects or events in the social and physical world con- etituting the environment. The Fields of Psychology. — In this book, which is devoted primarily to general psychology, we shall be mainly concerned with the facts and principles of normal human consciousness, its constitution, its modes of operation, and its development. But we shall avail ourselves, wherever feasible, of useful ma- terial from various allied fields, such as child psychology, abnormal psychology, and animal psychology. Child psychology is occupied with the study of the mental processes of infants and young children, with special refer- ence to the facts of growth. Ainormal psychology has to do (1) with the study of the unusual phases of conscious process, such as are met with in trance, hallucinations, hypnotism, etc.; and is concerned (2) with the more definitely diseased forms of mentality, such as characterise insanity. Individual psychology: As is well known, individuals vary from one another in many ways as regards the precise texture of their minds. For example, certain persons have good memories for visual experiences, others for .auditory. Certain people enjoy music, to others it is an affliction. Many 4 PSYCHOLOGY persons are stolid in temperament, whereas others are highly excitable. The study of such personal traits as these is called individual psychology. The term variational psychology is often employed to cover not only investigation of these purely individualistic differences, hut also the study of racial and other group peculiarities such as are revealed in social psychology and folk psychology. Within this field of varia- tional psychology would fall the study of genius, of the criminal, of sex differences, of mental types and tempera- ments. Almost all the great fields of human interest and experience are now studied from the side of psychology and we hear accordingly of religious psychology, of the psychology of art, of educational psychology, and so forth. Social psychology, in its broadest sense, has to do mainly with the psychological principles involved in those expressions of mental life which take form in social relations, organiza- tions, and practices, e. g., the mental attributes of crowds and mobs as contrasted with the mental characteristics of the in- dividuals constituting them. A branch of social psychology, often known as folk psychology, or race psychology, is con- cerned with the psychical attributes of peoples, especially those of primitive groups as contrasted with civilised nations. The development of language affords one of the interesting problems in this field. Animal psychology, frequently called comparative psy- chology, is engaged with the study of consciousness, wherever, apart from man, its presence can be detected throughout the range of animal life. The term comparative psychology is also applied more broadly though more accurately to those branches of psychology, such as child psychology, abnormal psychology, social and race psychology, as well as animal psychology, in which the phenomena studied are compared with other ranges of mental activity, especially with the psychical processes of normal adult human life. Those phases of psychology which touch particularly upon the PROBLEMS OF PSYCHOLOGY 5 phenomena of development, whether racial or individual, are usually designated genetic psychology. The Methods of Psychology. — (1) Introspection. — The fundamental psychological method is introspection. Intro- spection means looking inward, as its derivation indicates. As a psychological method it consists simply in the direct examination of one's own mental processes. Much mystery has been attached to the fact that the mind can thus stand ofE and observe its own operations, and criticism has been lav- ishly devoted to proving the impossibility of securing scien- tific knowledge in any such fashion as this. But it is an un- deniable fact that by means of memory we are made aware of our mental acts, and we can trace in this manner by care- ful and systematic observation many of the rudimentary facts and principles peculiar to human consciousness. When a number of us cooperate in such introspective observation, we greatly augment the exactness and the breadth of our results, and the accepted doctrines of psychology have actually been established by the successive observations of many investi- gators in much this manner. (2) Objective Observation. — Moreover, we are able to supplement introspection by immediate objective observa- tion of other individuals. It is thus possible, for example, to detect much which is most characteristic of the emotions, such as anger and fear, by watching the actions of persons about us and noting their expressions, their gestures, etc. The facts' which we thus obtain must of course be interpreted in terms of our direct knowledge of our own experience, gained introspectively. But such observation of others often makes us sensitive to psychological processes in ourselves, which we should otherwise overlook. Finally, it is clear that our psychological facts, whether gained from observation of ourselves, or of others, must be made the subject of careful reflection and systematic arrangement before they can become of scientific value; otherwise they would be purely hap- 6 PSYCHOLOGY hazard, disconnected fragments, with no more meaning than any other collection of odds and ends. The need of such orderly reasoned arrangement is no more and no less true of the psychological facts gained by observations of others, or by introspection, than it is of physical facts discovered in any realm of science. The facts of gravity had been noticed again and again, but it required the ordering mind of a Newton to set them in intelligent array. Whenever we speak of objective observation, or of introspection, as methods, we shall understand, therefore, this systematic and scientific implication of the terms. The remaining psychological methods which we shall mention are simply developments of these two in the direction of systematising, perfecting and extending their employment. (3) Experiment. — Experimental psychology, sometimes Bpoken of as "the new psychology,^^ or the "laboratory psy- chology," is perhaps the most vigorous and characteristic psychological method of the present day. It is simply an in- genious system for bringing introspection and observation under control, so that their results can be verified by different observers, just as the result of a chemical experiment may be verified by anyone who will repeat the conditions. In every branch of science an experiment consists in making observa- tions of phenomena under conditions of control, so that one may know just what factors are at work in producing the results observed. A psychological experiment is based on pre- cisely the same principle. The larger part of the psychological investigation con- ducted by means of these several methods has thus far been devoted to the qualitative analysis of consciousness. In recent years, however, the development of experimental procedure has stimulated an increasing interest in tlie study of the quantitative aspects of mental process. Because of this fact a sharp distinction is occasionally made nowadays between qualitative and quantitative psychology. PROBLEMS OF PSYCHOLOGY 7 (4) Physiological Psychology and (5) Psychophysics. — Physiological psychology and psychophysics, which are both closely connected, in spirit and in fact, with experimental psychology, are especially devoted to investigating the rela- tions between consciousness on the one hand, and the nervous system and the physical world on the other. Much of physi- ological psychology, and all of psychophysics, is experi- mental so far as concerns the methods employed. They both furnish information supplementary to that gathered by ordinary introspection and observation. Psychophysics forms a part of the larger field of quantita- tive psychology to which reference has just been made. Its aim is to reduce to quantitative formulae the relations of con- scious processes to the physical world. For instance, it attempts to determine the exact physical changes in the in- tensity of light necessary to produce noticeable changes in the sensations which light occasions. Physiological psy- ^ chology on the other hand is devoted primarily to determin- , ing the correlation between the activities of the body, particu- larly of the nervous system, and the various forms of con- scious process, such,, for example, as vision and hearing. We shall make frequent use of material drawn from this source. Relations between the Various Methods and Fields of Psychology. — Evidently certain of these methods are applica- ble to more than one field of psychological investigation. Observation is valid everywhere. Experiment can be em- ployed with children, with adults and with animals. Intro- spection is available with normal adults and can often be used with children. Many abnormal conditions permit its use. Other inter-relations will readily suggest themselves. The Psychologist's Standpoint. — In our study of mental processes we shall adopt the biological point of view Just now dominant in psychology, and regard consciousness, not as a metaphysical entity to be investigated apart from other things, but rather as one among many manifestations of 8 PSYCHOLOGY organic life, to be understood properly only when regarded in connection with life phenomena. We shall discover, as we go on, abundant reason for the belief that conscious processes and certain nervous processes are indissolubly bound up with one another in the human being. But at this point, without attempting to justify the assertion, we may lay it down as a basal postulate that the real human organism is a psychophys- ical organism, and that the mental portion of it is not to be completely or correctly apprehended without reference to the physiological portion. The psychophysical organism is, moreover, a real unit. The separation of the mind from the body which we commonly make in thinking about them is a separation made in behalf of some one of our theoretical or practical interests, and as such, the separation is often serviceable. In actual life experience, however, the two things are never separated. Therefore, although our primary task is to analyse and explain mental facts, we shall attempt to do this in closest possible connection with their accom- panying physiological processes. Our adoption of the biological point of view, while it im- plies no disrespect for metaphysics, will mean not only that we shall study consciousness in connection with physiological processes wherever possible, but it will also mean that we shall regard all the operations of consciousness — all our sen- sations, all our emotions, and all our acts of will — as so many expressions of organic adaptations to our environments, an environment which we must remember is social as well as physical. An organism represents, among other things, a device for executing movements in response to the stimulations and demands of the environment. In the main these move- ments are of an organically beneficial character, otherwise the creature would perish. Mind seems to involve the master devices through which these adaptive operations of organic life may be made most perfect. We shall consequently attempt to see how the various features of consciousness are PROBLEMS OF PSYCHOLOGY 9 concerned in this adaptive process. Let it not be supposed that such a point of view will render us oblivious of, or in- sensitive to, the higher and more spiritual implications of con- sciousness. On the contrary, we shall learn to see these higher implications with their complete background, rather than in detachment and isolation. Psychology and Natural Science. — In one important par- ticular the method of psychology follows the procedure of the natural sciences, such as physics, botany, and geology. Psy- chology takes for itself a certain definite domain, i. e., consciousness as a life process. Moreover, it starts out with certain assumptions, or postulates, as they are called, about its subject matter, w'hich it refuses to challenge. The chemist, for example, never stops to inquire whether matter really exists or is simply an illusion. He assumes its reality with- out question, and forthwith goes about his business. So the psychologist assumes in a common-sense way the reality of mind and the reality of matter. Nor does he question that . mind can know matter. These assumptions prevent the necessity of his untangling the metaphysical puzzles which are involved at these points, and leave him free to investigate his field in a purely empirical way. He also attempts, wherever possible, to emulate the natural scientist's use of the idea of causation. Our most reliable forms of knowledge about nature are based upon our knowledge of cause and effect relations. A great deal of our chemical knowledge is in this way exceedingly precise and exact; whereas the lack of such knowledge renders much of our acquaintance with disease extremely superficial and unreliable. The subject matter of psychology evidently brings it into a distinctly universal relation to all the other sciences, for these sciences are severally engaged in the development of knowledge, and the knowledge-process is itself one of the subjects in which psychology is most interested. Psychology and Biology. — Inasmuch as psychology is lO PSYCHOLOGY occupied with life phenomena, it is clearly most nearly related to the biological sciences. Indeed, as a natural science it obviously belongs to the biological group. This relationship is as close in fact as it is in theory. The modern psychologist makes frequent use of material furnished him by the anat- omist, the physiologist, the zoologist, and the alienist, and he gives them in return, when he can, such psychological facts as they find it necessary to employ. Psycliology and Philosophy. — Psychology has developed historically out of philosophy, and although it is now in many ways practically independent, its relations with philosophy- are necessarily very intimate. The connection is particularly close with those branches of philosophy commonly called normative, i. e., ethics, logic, and aesthetics. These inquiries are respectively concerned with questions of right and wrong, truth and error, beauty and ugliness. It is evident that the profitable discussion of such problems must involve a knowl- edge of the mental operations employed when we make a right or wrong choice, when we reason falsely or truly, when we experience pleasure in listening to music, etc. In a sense, therefore, psychology furnishes the indispensable introduc- tion to these several philosophical disciplines. It affords an acquaintance with the mental processes which lead respec- tively to conduct, to knowledge, and to the creation and appreciation of art. It thus enables an intelligent appre- hension of the problems which arise in these spheres, and furnishes much of the material essential for their solution. A similar thing is true, though in a less conspicuous and obvious way, of the relation of psychology to metaphysics, and to that form of metaphysical inquiry which formerly was known as rational psychology. By rational psychology was commonly understood the in- quiry into the conditions rendering the existence of conscious- ness possible. Evidently these inquiries, i. e., rational psy- chology and metaphysics, together with what is known as PROBLEMS OF PSYCHOLOGY II epistemology, or the theory of knowledge, are engaged with Just such problems as underlie the assumptions of psychology and the natural sciences, e. g., the reality of matter, its inde- pendence of mind, etc. It is on this account that metaphysics is said to be the science of sciences. It attempts to apprehend the essence of reality, to solve the problem of the ultimate nature of mind and matter and their relations to one another. Although metaphysics is in this sense more fundamental than psychology, and logically antecedent to it, it is so extensively concerned with mental processes, that a knowledge of psy- chology is commonly recognised as practically indispensable for its effective conduct or apprehension. All these branches of philosophy clearly involve, as does psychology, the study of consciousness in a certain sense. But whereas these dis- tinctly philosophical disciplines are primarily interested in some one or another of the implications and products of thought processes, psychology is interested primarily in the constitution and operation of consciousness itself. We may question whether ultimately there are any hard and fast lines severing these philosophical inquiries from one another and from psychology. The distinctions are perhaps rather practical than ultimate. One inquiry inevitably shades ofl into the others. Psychology and Education. — Psychology is related to educational theory in much the way that it is to ethics. It may be said to be related to actual educational procedure as theory is to practice. Education has as its function the symmetrical development of the powers of the individual. What the natural relations may be among these faculties, what are the laws of their unfolding, what the judicious methods for their cultivation or repression — these and a thousand similar practical questions can be answered by the assistance of psychological observation, or else not at all. The result which we desire to attain in our educational system must be, in a considerable measure, determined by the social and 12 PSYCHOLOGY ethical ideals we have in view. But the securing of the re- sults, the realising of the ideals which we have set up, through our educational machinery — this must be accomplished, if we would work with true insight and not by blind experi- ment, through a real knowledge of human mental processes. We shall keep constantly before us in this book the facts of growth and the facts of adaptation to the demands of the environment. Clearly these are the facts of practical signifi- cance for educational procedure. CHAPTER II THE PSYCHOPHYSICAL ORGANISM AND THE NERVOUS SYSTEM The Union of the Psychical and the Physical in the Organism. — We shall now examine some of the evidence con- firmatory of our assertion in the last chapter, that conscious processes and physiological processes are intimately connected in the organism. We shall in this way discover some of the reasons why it is desirable for us at the outset of our study of mental life to learn something about the nervous system, to which subject we shall then devote the remaining portion of the chapter. Evidence from Familiar Facts. — Common observation informs us of at least two fundamental types of fact con- cerning these mind-body relations. We know in this manner (1) that our consciousness or knowledge of the world about us depends primarily upon the use of our senses. A person born blind and deaf has neither visual nor auditory sensa- tions or ideas, and never can have, so long as he remains desti- tute of eyes and ears. By means of the other senses he may be taught much about colours and sounds, as Helen Keller has been, who lost her sight and hearing in infancy; but he never can have the experience which you or I have, when we see a colour or hear a sound, or when we permit a melody "^to run through our heads," as we say, or when we call into our minds the appearance of a friend's face. Indeed, if a child becomes blind before he is five years old he commonly loses all his visual ideas and memories just as completely as though he had been born blind. There is every reason to believe that if we were deprived of all our senses from birth, 14 PSYCHOLOGY we could never possess knowledge of any kind. The senses thus hold the keys which unlock the doors of intelligence to the mind, and the senses are physical, not mental, things. Apparently, therefore, the most simple and fundamental operations of consciousness are bound up with the existence and activity of certain bodily organs. Common observation also informs us (2) that the expres- sions of mind ordinarily take the form of muscular move- ments which we call acts. We hear a bell and our conscious- ness of the sound results in our going to open the door. We consider a course of action, and the outcome of our delibera- tion issues in the form of words or deeds, all of which con- sist primarily in muscular movements. Strange as it may appear, even keeping still involves muscular activity. It would accordingly seem as though the mind were hemmed in between the sense organs on the one hand and the muscles on the other. It would be a truer expression of the facts, however, to say that these are the tools with which the mind works. Through the sense organs it receives its raw material, and by its own operations this material is worked up and organised into the coherent product which we call intelli- gence. This intelligence is then made effective in practical ways through the rationally controlled action of the voluntary muscles. There are other facts of a well-known kind whose precise purport is, perhaps, less evident, but whose general implica- tion of intimate connections between mind and body is iden- tical with that of the considerations which we have Just mentioned. We know, for example, that blows and wounds may seriously disturb consciousness, or even destroy it. The similar effects of many drugs, such as alcohol, ether, and hashish, are matters of common knowledge. Even coffee and tea exercise a mild influence upon our psychical mood; and the change in general disposition which frequently fol- lows indulgence in a satisfactory meal is a phenomenon THE PSYCHOPHYSICAL ORGANISM 1 5 familiar to every family circle. Bodily disease often pro- duces a most marked effect upoii the mind, and conversely the different effect upon certain diseases, of a cheerful or a depressed mental attitude, is a subject of frequent remark. Evidence from Scientific Facts. — When we examine the less familiar evidence offered us by certain branches of modern science, we iind our previous impressions strongly confirmed. Thus we learn from pathology, the science of disease, that disordered conditions of particular portions of the brain tissue are accompanied by disturbances of definite kinds in con- eciousness. In this way we learn, for example, that the destruction or disintegration of the tissue of one region in the brain is followed by the loss of one's visual memories, so that one cannot recall the appearance of familiar objects. A similar disorder in another region costs one the control of certain muscles in the hand, etc. The science of anatomy is able to demonstrate structural connections of nerves be- tween these diseased parts of the brain and the sense organs and muscles over which consciousness has lost control, thus supporting the implication of the pathological evidence already cited. Experimental physiology shows us, that by stimulating (either mechanically or electrically) certain brain areas in animals, we can produce movements of definite muscles, whereas by extirpating these regions we can at least temporarily cripple the muscles and render the will power- less over them. By similar excisions of other brain areas we can cripple definite sense organs. Muscular movements are als© elicited by stimulating the surfaces of the human brain in cases where accident or operation has exposed the proper regions. Thus pathology, anatomy, and physiology all point to the same intimate relation of mind and body and indicate more specifically than the observations of every-day experi- ence could do, a fixed and positive relation between definite parts of the nervous system and such special phases of con- sciousness as the visual, the auditory, etc. l6 PSYCHOLOGY Moreover, comparative anatomy, comparative physiology, and comparative psychology all converge upon another cognate principle, i. e., that the development of consciousness among various genera and species of the organic world has run parallel with the development of the nervous system. Taking all these considerations into account, the deliverances of common sense as well as the teachings of science, it is easy to understand why the modern psychologist finds it judi- cious in his study of consciousness to learn all that he can about the nervous system, the sense organs, and the motor mechanism. The Nervous System. — It will assist us in gaining a work- ing idea of the nervous system to bear in mind the fact that its fundamental function consists in the conversion of incom- ing nerve impulses into outgoing nerve impulses causing movements of a kind tending to preserve the creature. The stimulations to which it responds are such things as light, heat, sound and mechanical pressure, together with various other physical and chemical processes of nature. Creatures destitute of some form of nervous system are practically in- capable of prompt and appropriate adaptation to their sur- roundings. Plants are thus in large measure the passive victims of their environments. Injury to one part commonly produces little or no immediate effect upon the rest of the plant. But by means of its nervous system every part of an animal organism is brought into vital connection with every other part and with the outside world. Adaptive cooperation becomes the controlling principle in the life activities. This cooperation, or coordination, takes the form of movements made in response to sensory stimulations, and the most highly evolved type of nervous system, such as that of the human being, differs from a very rudimentary one, like that of the jelly fish, only in the form and complexity of the devices by which these stimulations and movements are con- nected. When studying the structure of the nervous systenu THE PSYCHOPHYSICAL ORGANISM 27 it should always be remembered that this fact about the co- ordination of stimuli and movements offers the clue by which even its most intricate arrangements may be interpreted. The Elementary Structures. — The nervous system is made up of elementary structures called neurones. A sketch Fig. 1. Isolated body of a large cell from the ventral horn of the spinal cord of man. Multiplied 200 diameters (Donaldson after Obersteiner) . A, axone (each cell has but one); D, dendrites; JV, nucleus with enclosures; P, pigment spot. of certain common forms of neurones is shown in figures 1, 2, and 3.* It will be seen that the neurone is a protoplasmic structure made up of a cell-body containing a nucleus, and often within this nucleus smaller neucleoli, while from its •This chapter cannot be thoroughly mastered without a careful study of the cuts and diagrams. The conception of the nervous system which is adopted is that at present generally prevalent among neurologists. It must be remembered, however, that the science of neurology is growing with astonishing rapidity, and radical changes of doctrine are consequently possible at any time. tS PSYCHOLOGY Fia. 2. A, cell from the spinal ganglion; B, cell from the ventral horn of spinal cord; C, cell from the sympathetic, D, cell from the spinal cord; E, pyramidal cell from the cerebral cortex; F, cell from the cerebellar cortex; a, axones; d, dendrites; c, col- laterals; p, peripheral part of the fibre; cl, central part. Arrows indicate the direction of conduction for nervous im- pulses. (Modified from Morria and from Toldt.) THE PSYCHOPHYSICAL ORGANISM 19 surfaces are given off filaments of various forms and sizes. The filaments range in length all the way from a fraction of a millimetre up to five feet, and in bulk they generally ex- ceed the cell-body very much. The whole structure, includ- ing both filaments and cell-body, constitutes the neurone. It has been estimated that in the nervous system of the adult Fig. 3. A-D, showing the phylogenetic development in a series of vertebrates ; a-e, the ontogenetic development of growing cells in a typical mammal; in both cases only pyramidal cells from the cerebrum are shown; A, frog; B, lizard; C, rat; D, man; a, neuioblast, or young cell, without dendrites; 6, commencing dendrites; c, dendrites further developed; d, first appearance of collateral branches; e, further development of collaterals and dendrites ; ax, ax ones ; de, dendrites ; cl, collaterals. ( Modified from Donaldson after Ramon y Cajal.) human being there are about 11,000 millions of these neurones in various stages of development. Their average volume is probably about .00009 of a cubic millimetre. Certain of the fibrous processes of the neurones are called 20 PSYCHOLOGY axones or neurites, others are known as dendrites. The ax- ones, as may be seen from figures 2 and 3, are generally smooth in their contours, and when they branch, the divisions commonly occur at right angles. Each neurone has but a single axone. These axones are the 'fibres' of common par- lance, the dendrites being from the structural point of view D A.X, 3.2. 1. A X. Fig. 4. A, diagram of niediillated nerve fibre; 1, the axis cylinder; 2, the medullary sheath; 3, the primitive sheath or neurilemma; B, a sketch of medullated nerve fibre; AX, axis cylinder; M, medullary sheath; P, primitive sheath; N, node of Ranvier; G, fibres of the sympathetic system. They are in the main un- medullated; D, a cross section of B showing the same struc- tures. (Modified from Toldt and Thorndike.) essentially parts of the cell-body. Within the central nervous system the dendrites are rougher and branch more gradually from one another, somewhat like the sticks of a fan. The fully developed axones have a peculiar structure, shown in figure 4. The central strand is known as the axis cylinder. This is a transparent mass which constitutes the true nerve. THE PSYCHOPHYSICAL ORGANISM 21 and conducts the nervous impulses from one point to another. Outside the axis cylinder is a relatively thick covering known as the medullary sheath. This sheath is secondarily acquired and generally disappears near the cell-bodies and also wherever the fibre terminus approaches other fibre terminals. Outside of this again there is a thin nucleated membranous sheath known as the neurilemma; found;, however, only out- side the central nervous system, i. e., in regions outside the spinal cord and brain. Functions of Elementary Structures. — Although the cell- body and fibre are really parts of a single organic cell — the neurone — their notable difference in appearance is accom- panied by certain differences in function. Both cell-bodies and fibres are sensitive to stimulation, are irritable, as the physiologists say, and both possess conductivity. In addition to these functions the cell-bodies have ordinarily been sup- posed to possess the capacities of either reinforcing or in- hibiting the impulses sent to them. It has also been belieyed that at times they send out nervous excitation along the fibres without any detectable external stimulation, i. e., that their action is occasionally automatic. Whether the cell- bodies really possess these properties or not, at least they furnish a rich system of interconnections for the neurones by means of the fibres which radiate from them as centers. It seems to be well established, too, that the cell-bodies exercise highly important nutritive functions. Certainly if the cell-body be destroyed, the fibre promptly dies. Indeed, certain neurologists hold that the cell-body is not necessarily involved in the truly nervous activity of the system at all, but is mainly confined to these nutritional functions. Eecent investigations strongly suggest that the places at which neurones come into active relations with one another, i. e., their terminals, are much more important than had been suspected. Some of the functions formerly attributed to the cell-bodies, particularly those of inhibition, may be prop- 22 PSYCHOLOGY erties of these junction regions. The term 'synapsis' is gen- erally used to designate these unions. The nature of the contacts will be described presently. On the whole it seems doubtful whether the differences between the nervous functions of the cell-bodies and the fibres are as marked as was until recently believed, but in any case the neurones are so linked together as to bring sensitive end-organs, like the eye and ear and the nerves of the skin, into relations with (1) the various nervous cen- ters of the brain and spinal cord, and through these with (2) the muscles and glands. It is supposed that inside the central nervous system the axones are ordinarily employed to carry impulses away from the cell-bodies, whereas the dendrites probably carry impulses toward them. Outside the central system the afferent fibres leading to the spinal ganglia resemble axones in structure, and so offer apparent exceptions to this rule. Moreover, in certain cases the axones seem to be given off from dendrites, so that the nervous current in passing from one to the other need not enter the cell-body. Whether this appearance be misleading or not, the usual arrangement is undoubtedly one in which the cell-body intervenes between the axone and the dendrites. In any event the whole nervous system is nothing but an aggregation of neurones, in a frame of connective tis- sue, blood-vessels and lymphatics combined, with the support- ing tissue, called neuroglia, which holds the neurones in place. A nervous impulse originating in the sensory surface of- the body, for example in the retina, may be transmitted from one group of neurones to another, until finally it issues, per- haps, from the nerves of the spinal cord, and produces a movement of the foot. This is what would occur if one should step aside upon seeing a heavy object about to fall. In this process of transmitting the impulse through the nervous system, it Is not necessary that the groups of neurones should be actually in contact with one another, although THE PSYCHOPHYSICAL ORGANISM 23 this may occur. But they must at least be close together. The Nervous Current. — The exact physical nature of neural excitement is not known. Various theories have been propounded in the effort to identify it with recognised forms of chemical or electrical activity, but thus far no hypothesis has been suggested which accords satisfactorily with all the facts. Meantime, we speak of the nervous current, the neural disturbance or excitement, in a purely metaphorical way, to cover the facts which we do know, i. e., that physiological activity of a certain kind occurs in the nervous structures, and Is transmitted very rapidly from one point to another. In man the rate of this transmission is about 100 feet per second. Various Forms of Nervous System. — When we turn to the zoologist and the comparative anatomist, we are able to obtain certain interesting facts about the development of the ner- vous system throughout the organic kingdom. From such sources we learn that the simplest t3rpes of animal organism, e. g., such protozoans as the amoeba, possess no nervous system at all. Every part of the surface of the unicellular amoeba (figure 5) is capable of movement, of assimilating food and excreting the waste pro- ducts. This animal's be- haviour suggests that other forms of tissue besides ner- vous tissue are sensitive and capable of conducting Fi^S. Diagram of an impulses. Undoubtedly this amoeba. The irregularly IS a fact, and we must shaped _ mass of proto- • accordingly think of the plasm IS shown with N, . its nucleus, and CV, a nerves as Simply special- contractile vacuole, which jged forms of protoplasm expands and contracts. . '- ^ m which these functions are more highly developed than elsewhere. In certain of the lower metazoans nerve cells appear with fibres extend- ing toward the periphery of the body and possessing sensitive 24 PSYCHOLOGY terminations. Among the coelenterates a very simple nervous system comes to light. In hydroids this is merely a kind of tissue of nerve cells. In echinoderms we meet with a struc- ture like that shown in figure 6. But it is not till we reach such forms as the worms that we find a definite organised centre of con- trol, like the brain or spinal cord. In the an- nulates of the worm forms there is not only a centre corresponding to a very rudimentary brain, but also one roughly cor- responding to the spinal cord. (Figures 7 and 8.) Fig. 6. Nervous system of a star- ^^ ^^^ molluscs the de- fish; a, central nerve ring that velopment is made more surrounds the mouth; b, periph- complex by the appear- era! nerves of the arms. (After r J rr Loeb.) ance of these groups of central cells clustered together in several directions about the brain. (Figure 9.) Even in the lowest forms of vertebrates, e. g., the acranial amphioxus, we find both a brain and cord. Passing from the lowest to the highest verte- brates up, for example, through the fishes, amphibians, and reptiles to the birds and mammals, we meet with every shade of variation in the development of the several parts of the nervous system. Everywhere, however, from the most primi- tive metazoan up to man, the general principle is one and the same — a mechanism for connecting sensitive receptive organs with muscles and glands.* The Development of the Gross Structures of the Human *Readers who wish simply a general impression of brain organi- zation and action, as related to consciousness, rather than a more detailed knowledge, will do well to omit from this point to the paragraph on page 39 dealing with the cerebrum. THE PSYCHOPHYSICAL ORGANISM 25 Ok -, 0. r^^,^xi_z__ni System. — If we were to examine the human nervous system at one period of its embryonic development, we should find it a crude structure of tubular form, with one end enlarged, and slightly constricted at two zones, as shown in figures 10, A, B, C. In certain regions the walls of this en- larged portion thicken and spread out as they grow, whereas in several places they dwindle away to a mere membrane. In this manner the various parts of the adult brain are formed, re- taining to the end the old tubular contours. The rem- nant of the cavities in the embryonic brain and cord become respectively the ven- tricles of the developed brain and the canal of the spinal cord. (Figures 11 A and B.) These cavities remain connected with one another and are filled with the cere- brospinal fluid. The sur- faces of the brain and cord are closely invested with a membrane, the pia mater, carrying blood-vessels. This ^'*^- ^- '^}''\ brain and a series of '' ^ . segmental ganglia of an annelid membrane is bathed on its (Nereis) : o, supraoesophageal outer surfaces by fluids. A ganglion, or brain ; c, commis- ^ sure; u, suboesophageal gang- tough, thick membrane, the lion. (Loeb after Clapargde.) dura mater, separates the pia mater from the bones of the skull and vertebrae. (Figures 12 and 13 show the external appearance of the nervous system.) 26 PSYCHOLOGY S. G. r- o. The portion of the embryonic brain known as the fore- brain finally develops into the great masses of the cere- brum. [See in explanation of this paragraph figures lOB and C, 11 A and B, 13, 13, and 14.] The optic thalami, which are large collections of nerve cells with their fibrous connections, also belonged originally to this general region of the brain. The primitive mid-brain changes less in mass during growth than does the fore-brain, and becomes on its under or ven- tral surface the crura or peduncles of the brain, while on its upper or dorsal surface it becomes the corpora quad- _, „ ^ , . ^ , , rigemina. The hind-brain de- ±IG. 8. Dorsal view of central ner- " Yous system of an earthworm; Velops m its foremost part, 0, supracesophageal ganglion; c, dorsally into the cerebellum, commissure; u, subcesophageal -, , n ■ ganglion; ;Sf, pharynx; G, gan- and ventrally mto the pons, glia of the ventral cord. Jq its lower portions it be- ( After Loeb.) /n n x comes the medulla oblongata, upon the dorsal surface of which appears the fourth ventricle, with its non-nervous membranous covering. The spinal cord undergoes the least profound change, as regards its external contours, of any of the embryonic parts of the central system. When we take the facts of development into account, there- fore, it becomes evident that the various portions of the brain, which seem at first glance so hopelessly confused in their relations to one another, are nevertheless all derived from a single relatively simple structure — the tubular em- bryonic nervous system. This is modified by certain flexures and inequalities of growth, but its walls are everywhere made up of neurones and their supporting tissues, the neuroglia. THE PSYCHOPHYSICAL ORGANISM 27 The general form of the brain is complete some time before birth. The number of neurones, the nervous element, is also com- plete at birth, though by far the larger portion is not mature or functionally active at this time. ' But the approximate maturity of the brain in point of size and weight is not reached until about seven years of age, and develop- ment in the interconnec- tions of the neurones goes on indefinitely, certainly with most persons up to forty years of age. Eecent investigations indicate that the weight of the brain diminishes after the twen- tieth year. A Functional Grouping of Neurones. — The neu- rones of the central sys-^^^^g^ Brain of a mollusc (Sepia); tem may be grouped Gg, cerebral ganglion ; Spg, sup- according to certain of ^acesophageal ganglion; B^r buccal ° ganglion; Tg, ganglia 01 the ten- their functions in three tacles. (Loeb after Glaus.) great divisions : ( 1 ) sensory neurones which bring nervous impulses in from the sense organs (Fig. 15A), (2) motor neurones which terminate in muscles and carry to them im- pulses from the nervous centres (Fig. 15B), and (3) central neurones which in various ways join together the members of the first two groups (Fig. 2, D to F). As we remarked earlier in the chapter, the nervous system seems to manifest its essential value as a device whereby appropriate move- ments are made in response to sensory stimulations. These three great neurone divisions represent therefore the funda- mental elements in such a device, i. e., mechanisms for trans- mitting stimuli inward, for transmitting them outward again 28 PSYCHOLOGY and for combining the several sensory varieties of stimu- lation with the most varied kinds of muscular response. Th. B Fig. 10. A, B, C Diagrams illustrating embryological clianges in the brain, Av, anterior vesicle, or fore-brain ; M-b, middle vesicle or mid-brain; Pv, posterior vesicle, or hind-brain; H, cerebral hemi- spheres; Th, thalamus; Cb, cerebellum; Mo, medulla oblongata. (James after Huguenin.) The sensory neurones leading from the different sense organs, i. e., in the eye, ear, nose, tongue, skin, muscles, tendons and other deep-lying tissues, put the organism in contact vs^ith the most diverse forms of motion in the physical world, e. g., light, sound, temperature, etc.* It is as though the organism were supplied with so many telephones sensitive to each of these forms of physical communication. We shall describe the sense organs in the chapter on sensation. Among the vast numbers of central neurones we shall find those of the cerebral cortex most significant for mental life. It is with these that the fate of our conscious processes seems most intimately hound up. The action of the central neurones becomes finally effective through the discharge of their ner- vous energy into the motor neurones. Such discharges *It v^ill of course be understood that the immediate sensory stimu- lus to the nerves of the muscles, tendons and joints is ordinarily muscular movement. The subject is further discussed, together with certain other intra-organic sense processes, in the chapter on sen- sation. THE PSYCHOPHYSICAL ORGANISM 29 occasion our muscular movements and lead to the various acts which constitute our conduct — the things we say and the things we do. Ail Anatomical Grouping of Neurones.— Following Eb- binghaus and others we may also classify the neurones of the central nervous system on an anatomical basis in three gen- eral groups, (1) the peripheral neurones, (2) the subcortical neurones, and (3) the cortical neurones. This classification is based on the location of the cell-bodies of the neurones and it must not be understood as invalidating the first classi- S. Ca. B. Fig. 11. A.B. Diagrams to illustrate the position of the ventricles and the spinal canal with the connecting channels. The figure at the left represents the ventricles as seen from the right side projected against the outline of the brain. The figure at the right represents diagrammatically a cross section through the ventricles as seen from in front projected against the outer con- tours of the brain. Cer., the cerebrum ; LV, the lateral ven- tricles; ///, the third ventricle; Aq.8., the aqueduct of Sylvius joining the third and fourth ventricles; IV, the fourth ven- tricle; Cb., the cerebellum; S.Ca., the spinal canal. fication. The two groupings are supplementary to one another. The first method of division gives us a rough working impression of how certain of the nearones differ in the service they render, without much regard to their relative positions. The present classification affords a much 30 PSYCHOLOGY Cer Figs. 12 and 13. Figure 12 at the left shows the general relations of the central nervous system to the bones of the skull and THE PSYCHOPHYSICAL ORGANISM 3 1 more detailed and accurate impression of their topographical relations to each other. Apparently no single classification will serve eqnally well to bring out the two kinds of relations.* Peripheral Neurones. — The peripheral neurones of this classification are substantially identical with the sensory neurones of the previous classification. Their cell-hodies lie outside the central system, i. e., outside the spinal cord and brain, and are sometimes situated near the central structures, as in the case of the cells in the ganglia of the posterior roots of the spinal cord. These cells of the spinal cord ganglia distribute their sensory fibres to the skin, muscles, tendons, etc. Sometimes, however, the cell-bodies of the peripheral neurones are in the neighborhood of the sense *0n the basis of recent investigations a division of the nervous system is proposed which promises to be very useful. The entire system, both central and sympathetic, is thought of as composed of four columns in each half of the body, eight altogether. ( 1 ) A sensory somatic, (2) a motor somatic, (3) a sensory visceral, and (4) a motor visceral. The first and second group would include all sensory and motor processes affecting the adjustment of the organism directly to the environment. The third and fourth divis- ions would include all processes concerned in the nutritional activi- ties. spine. Figure 13, at the right, displays the general contours of the central system as seen from in front. The great gan- glionated cord of the sympathetic system is shown attached to one side of the spinal nerves; the other side has been cut away. Cer., the cerebral hemispheres; 0, the olfactory centres; P, the pons Varolii; M, the medulla oblongata; Cb., the cerebellum; Sp.C, the spinal cord; /, the olfactory nerve; II, the optic nerve; ///, the oculo-motor nerve; IV, the trochlear nerve; V, the trigeminus nerve ; VI, abducens nerve ; VII, the facial nerve ; VIII, the auditory nerve; IX, glosso-pharyngeal nerve: X, the vagus nerve; XI, spinal accessory; XII, the hypoglossal nerve; C, the first cervical spinal nerve; Dj, the first dorsal, or thor- acic, nerve; L^, the first lumbar nerve; 8^, the first sacral nerve; Zi, filum terminale; CS^, superior cervical ganglion of the sym- pathetic; CS\ middle cervical ganglion of the sympathetic; O/Sf*, and DS^, junction of the inferior cervical and the first dor- sal, or thoracic, ganglion of the sympathetic; DS", the eleventh dorsal, or thoracic ganglion, pf the sympathetic; L8^, the first lumbar ganglion of the same system; 88\ the first sacral ganglion also of the sympathetic. S2 PSYCHOLOGY Fig. 14. Cer., the cerebral hemispheres ; fif.B., striate body of the left half of the brain; T., left half of the thalami; C.Q., corpora quadrigemina ; 3F, third ventricle; Aq.S., aqueduct of Sylvius; Cb., cerebellum; C, the crura, or pillars of the brain; P., the pons Varolii; 4F., the fourth ventricle; M., the medulla oblon- gata; S.Ca., the spinal canal; Sp.C, the spinal cord. The drawing is purely diagrammatic and should be interpreted in connection with figures 10, B and C, and 11, A and B. organ, as in the case of the auditory nerve, which arises from a cell in the internal ear; the optic nerve, which has its cell-body in the retina, etc. (See cuts in Chapter Y.) The function of the peripheral neurones is evidently that of transmitting impulses from the sense-organs into the nervous centres, and we need discuss them no further at this point. Subcortical Neurones. — The subcortical group involves all the gross structures in the central system save the cortices of the cerebrum and the cerebellum on the one hand and the peripheral (sensory) neurones on the other. Their function is in general that of furnishing neural mechanisms for the innervation of muscles and for connecting with one another the various parts of the central system below the cortices. This can be best brought out by examining separately some of the more conspicuous gross structures of this group. After THE PSYCHOPHYSICAL ORGANISM 33 doing this, we shall discuss the cortical groups, and their functions as general control centres. It will be appreciated at once that the subcortical neurones include both the motor neurones and the central neurones of the previous classifica- tion, except of course those of the cerebral and cerebellar cortices. The Spinal Cord.^We may first consider the spinal cord (figure 13). If we take a cross section of this organ, cutting through at right angles to its long axis, we find a structure ^^ Fig. 15. A, a peripheral sensory nerve originating in the gan- glion of the posterior fibre bun- dle of the spinal cord. N. E., free nerve ending in the skin; P. S. N., peripheral medul- lated nerve trunk; 8. G., spinal ganglion; A. B., ascending branch of the axone; D. B., descending branch of the same, both branches being inside the spinal cord proper; C. C, col- laterals from the axone. B, motor neurone of the ventral horn of the spinal cord send- ing a fibre dovpn to a muscle. D., dendritic processes; Ax., ax- one which takes on its medul- lary sheath as it passes out from the central nervous struc- ture of the cord; C, a col- lateral; P. M. N., the main body of the peripheral motor nerve; M., the muscle plate ending of the nerve on the muscle fibres. Arrows indicate in both A and B the direction in which impulses pass. (Modi- fied from Toldt.) such as is shown in figures 16 and 17. In the central por- tion, grouped about the spinal canal in the general shape of the letter H, is an area which appears a pink grey in the fresh state and which contains the cell-bodies of the neurones. 34 PSYCHOLOGY Fig. 16. Portion of cervical region of spinal cord. A, cord seen from anterior or ventral surface. B, cord seen from tlie lateral surface. 1, ventral median fissure; 2, dorsal sulcus; 5, ventral fibres leaving the cord; Q, dorsal fibres entering the cord; 7, spinal nerve after the union of the dorsal and ventral bundles of fibres; 7% fibres to and from the sympathetic system. (After Barker and Rauber.) Outside of this is a thick layer of white nerve fibres. Close examination of the grey matter reveals fibres running out laterally to penetrate the white masses. A large number of the fibres from the cell-bodies in the ventral or anterior region of the grey mass pass out from the spinal cord in bundles, finding exit between the several spinal vertebrae (figure 12). Thence they may be traced principally to the voluntary muscles of the limbs and trunk. These are the mo- tor neurones of the functional classification. The fibres enter- ing the dorsal or posterior region of the grey matter arise in the cells of the spinal ganglia and pass in similar bundles to the posterior side of the cord; while corresponding fibres on the distal side of the ganglia, after uniting with the THE PSYCHOPHYSICAL ORGANISM D P 35 Fig. 17. Diagrammatic cross-section of the spinal cord. W W, white fibrous matter; G G, grey cellular matter; A, afferent sensory fibres passing through S.G., the spinal ganglion, into the posterior horn of the grey matter; E, efferent motor fibres, most of which lead to muscles like M, many of which connect with the sympathetic ganglia, like 8y.; C, central cell probably traversed as a rule by impulses passing from A to E. D.P., dorsal, or posterior, surface of the cord; Y.A., ventral, or anterior, surface. bundles from the motor region, are distributed chiefly to the sense organs of the skin, joints, muscles, tendons, etc. It may be remarked at this point that the voluntary muscles, such as control the movements of the hand, are commonly striped muscles, whereas the involuntary muscles, e. y., those of the alimentary and circulatory systems, are generally unstriped. The unstriped muscles are mainly connected with the autonomic nervous system, of which we shall speak briefly a little later. The striped muscles contract and relax raore rapidly than the unstriped. Functions of the Spinal Cord. — The arrangement of the elements in the spinal cord suggests at once two of its prin- cipal functions, and is so typical of the facts generally char- acterising nervous structure and function that it seems judicious to comment upon it briefly. It will be observed in the first place that in the cord sensory and motor neurones, connected through their fibres with the sense organs and the muscles respectively, are in very close proximity to one another. It should be relatively easy, therefore, for an in- coming sensory impulse to find its way out over motor nerves 36 PSYCHOLOGY Anterior root Central motor pathway Motor ganglion cell Posterior root — ^ Ascending and ■^ descending branch of sensory fibre Motor nerve ending in muscle !-hil '' Se^^o^y collateral _j^ Cell and fibre of lateral column " Bipolar cell of spinal ganglion Fig. 18. Schematic representation of sensory and motor pcitliway^ in the cord. (After Toldt.) and so to produce reflex movements, that is, movements made in immediate response to sensory stimulations, without pass- ing to the brain and involving the guiding action of the cerebral cortex. This is precisely what happens, and it is as a reflex mechanism that the spinal cord exercises the first of its important functions. As instances of such reflexes we may mention the twitching of the toes and the jerking of the foot when the sole is tickled. The n-umber of these reflexes is large. Furthermore, we should find upon examina- tion that the white fibrous tracts along the external surfaces of the cord connect it with both the higher and the lower parts of the system. (Figure 18.) It should thus be easy for impulses to pass upward and downward, between the brain on the one hand and the sense organs and muscles on the other. Such ready transmission actually occurs, and it is in this fact that we find the second great function of this THE PSYCHOPHYSICAL ORGANISM 37 organ. The spinal cord is accordingly typical of the central structures in general, in that it provides (1) means for the immediate connection of sense organs and muscles and (2) devices for connecting various parts of its own and other nervous structures with one another. Functions of Other Suhcortical Groups of Neurones. — If we were to examine the other subcortical masses lying between the cerebral hemispheres and the spinal cord, we should find that, in general, they consist of aggregations of neurones much like those in the cord, but on the whole less simply and regularly disposed. Thus, the medulla, the cor- pora quadrigemina, and the thalami all display cell or neu- rone groups with sensory and motor connections. When we come to speak of their specific functions, we are obliged to indulge largely in speculation, because the facts are evi- dently extremely complex, and our knowledge of the details involved is notoriously incomplete. Moreover, the specialised functions which are sometimes attributed to them in the case of the lower animals are probably in the human being largely usurped by the cerebral cortex. In any event we must always remember that the nervous system is an organic unit, and no part of it ever acts wholly independently of the other parts, nor is any influence exercised upon one part entirely without significance for the other parts. Any mention of specific functions of dilferent regions must always be made with this reservation in mind. Thus, the spinal cord undoubtedly contains the neurones whose innervation is immediately re- sponsible for movements of the hand. But the stimulus to this innervation itself may originate almost anywhere throughout the rest of the nervous system, so that any por- tion of this system may in a particular case contribute to the production of the special motor consequences. To say that a region of the nervous system presides over any special func- tion is, therefore, simply to say that it is the portion most immediately and most invariably responsible for it. 38 PSYCHOLOGY Speaking within such limitations, we may say that there are two functions of centres lying in the medullic region, about which considerable unanimity of opinion exists. The automatic respiratory movements, and certain activities of the vaso-motor nerves (especially of the constrictors) which govern the calibre of the arteries, are controlled by neurones located in this neighborhood. These neurones discharge their impulses, however, in part through neurones in the spinal cord. Needless to say, all these regions are like the spinal cord in containing pathways for neural excitation to pass upward and downward, with the sense organs and the muscles as terminal points, between which the higher and the lower centres serve as intermediary connectors. Although the olfactory nerve is given off from the forward ventral region of the cerebrum, the remaining cerebral nerves issue from certain of the subcortical centres, e. g., the me- dulla, pons, thalami, etc. The cell-bodies from which these nerves originate are variously distributed in locations some- times at a considerable distance from the point where the nerve trunk penetrates the surface of the brain. This state- ment applies to the nerves of special sense like the auditory, the optic and the gustatory, together with such motor nerves as those controlling the eyes, the tongue, the lips, etc. Figure 13 shows the topographical relations. Segmental Character of the Central Nervous System. — It is commonly maintained that the structural pattern from which the human nervous system has been developed is of a segmental character, each part of it receiving sensory and motor nerves from relatively distinct regions, or seg- ments, over which they exercise a definite and sometimes exclusive control. Thus sensory nerves from the foot enter the same region of the spinal cord from which issue the motor nerves controlling the movements of the foot. Another region sustains similar relations to the trunk, another to the arms and so on. In the human being the motor nerves can, THE PSYCHOPHYSICAL ORGANISM 39 indeed, be classified without serious ambiguity in this seg- mental way in accordance with the special muscles which they innervate, e. g., those of the head, the upper trunk, the lower trunk, etc. But the complex central inter-connections of the sensory neurones in man — if we have in mind the way in which they operate and not simply their anatomical rela- tions — make any such segmental divisions of them very hazardous, so that the application of the segmental idea to the interpretation of our human nervous action is somewhat un- certain. The Cortical Neurones. — The Cerebellum. — So little is confidently known about the operations of the cortex of the cerebellum, that it will not be profitable to discuss it at length. Suffice it to say that by means of neurones which lead into it, as well as neurones which lead out, the cerebellum has a very rich connection with the cerebrum, the lower brain centres, and the sf)inal cord. The sensory connections with the latter organ are especially marked. It seems to be generally agreed that its functions are most intimately re- lated to the reception and coordination of the sensory stimu- lations which originate within the body itself, e. g., in the muscles, the viscera, the semicircular canals of the ear, etc. It is thus conspicuously involved in such actions as those by which we preserve our equilibrium and in general succeed in carrying forward well coordinated and balanced move- ments, like walking, sitting and standing. But just how it plays its part is not known. Certain authorities regard the evidence as warranting the assertion that the cerebellum is the chief locality for the reception of stimuli from the body itself, in contrast with the cerebrum which, they urge, re- ceives primarily stimuli from outside, and especially stimuli acting at a distance from the body, such as light and sound. The Cerebrum. — -For the psychologist the cerebral hemi- spheres are the most interesting and most important portions of the nervous system. Prom the various lines of evidence 40 PSYCHOLOGY mentioned earlier in the chapter, we know that consciousness is connected with this part of the brain in an exceedingly intimate way, and we shall consequently devote some little Figs. 19 and 20. Figure 19 shows the lateral surfaces of the right hemisphere of the cerebrum. Figure 20 shows the inner mesial surface of the left hemisphere. The section is made through the corpus callosum and the right hemisphere has been removed. The surfaces covered with colored dots are the so- called motor regions from which originate neurones in control of voluntary muscles. It is now generally held that this set of motor neurones is confined to the region in front of the fissure of Rolando, instead of being distributed on both sides of it, as was until recently regarded as the fact. Certain authorities are still disposed to maintain the older view. The sensory areas, which represent the receiving stations for sen- sory impulses from the periphery, are indicated by black dots. The regions most heavily dotted, in the case of both sensory and motor regions, are those most indispensable for the given function. The areas less heavily dotted are those which are either less uniformly employed in the exercise of the function, or whose derangement affects the secondary or more complex use of the function. For example, visual images and ideas may be disturbed by injuries which do not seriously impair crude sensations of sight. The areas free from dots are the association regions, which Flechsig has divided into a number of subordinate districts, but which we indicate without attempt to divide finely. R, the fissure of Rolando; M, motor regions; B, sensory regipu? for bodily sense impressions, e. g., touch, temperature, kinaesthetic. This region is often called the somsesthetic area. This region is now generally confined to the area posterior to the Rolandic fissure, but it is still held by certain authorities, as was formerly the common view, that the region extends in front of Rolando as well as behind it. V, visual centre; H, auditory centre; O, the olfactory centre, wliich extends in a great loop up over the corpus callosum. The extent of the area is at present quite uncertain and the drawing simply suggests the facts at present generally recognized. The confinement of motor and bodily areas to the region above the limbic lobe over the corpus callosum is also tentative, although asserted by competent investigators. O.B., the olfactory bulb; O.T., the olfactory tract; O.T.A., occipito-temporal association area; A.P., parietal association area, continuous with the occipito-temporal association area just mentioned; A.F., frontal association area; /., the island of Reil, another association area, to show which the cortical surfaces just above the fissure of Sylvius have been lifted up; C.C., corpus callosum. (Modified after Flechsig.) ^ F_^^ -_-... OTA Fig. 19 -,M^-AF OTA Fig. 20 THE PSYCHOPHYSICAL ORGANISM 41 How far the lower brain centres space to its consideration. in human beings may have directly to do with men- tal processes it is very difficult 1 say. The surface of the hemispheres, called the cortex, and shown in fig- ures 12, 13 and 19 to 21, is made up of layers of cell-bodies, with their delicate processes. Eoughly speaking the adult human cortex aver- ages about three millimetres in thick- ness. The extra- ordinary richness of the dendritic devel- opment in the cor- tical neurones fur- nishes one of the Fig. 21. Diagram showing cerebral hemi- spheres as seen from above. LF, longi- tudinal fissure separating the hemi- spheres; RR, fissure of Rolando. W, visual regions of the occipital lobes; AP, parietal association centres; AF, frontal association centres; MM, motor centres; BB, centres for bodily senses of touch, temperature, etc. most marked pecu- liarities of the human cerebrum, as contrasted with those of animals. This intricate dendritic structure appar- ently represents the bodily counterpart of those elaborate interrelations among ideational processes, which charac- terise in general the higher forms of intelligence. (Figure 22.) Cortical Sensory Centres. — Certain of the cortical areas are known to be in functional connection with sense organs 42 PSYCHOLOGY from which they receive stimuli. Thus, the region m.arked H is in connection witli tlie ear, and receives auditory im- pressions. (Compare figures 19 and 21.) Tlie region marked V is similarly connected with the retina, and re- ceives visual impressions. It is reasonably certain that the areas marked (figures 13 and 20) re- ceive olfactory stimuli, while the region marked B is probably that imme- diately concerned with the reception of tactual, ther- mal, kinsesthetic and or- g a n i c stimuli. The centres for taste are not clearly determined. It Fig. 22. Diagrammatic sec- tion of tile cerebral cortex taken at right angles to the surface. The right side of the drawing illustrates the fibre system alone, the left side illustrates primarily the cellular layers. The structure is so complex that it is difficult to dis- play both sets of facts in a single sketch. 1, molecular layer next the surface of the brain; 2 and 3, layers of pyramidal cells; 4, layer of polymorphous cells. 8. F., fibre of a sensory neurone entering to ter- minate in the outer molec- ular layer. (Modified from Morat.) seems probable, however, that they are in the neighborhood of the olfactory terminals. There is reason to believe that THE PSYCHOPHYSICAL ORGANISM L T. r. R.N. F 43 L.O.^ LOO Fig. 23. Scheme of the meclianisin of vision. (James after Seguin.) The cuneus convolution {Gu) of the right occipital lobe is sup- posed to be injured, and all the parts which lead to it are darkly shaded to show that they fail to exert their function. F.O. are the intra-hemispheric optical fibres. P.O.C. is the region of the lower optic centres (corpora geniculata and quad- rigemina). T.O.D. is the right optic tract; C, the chiasma; F.L.D. are the fibres going to the lateral or temporal half T. of the right retina, and F.G.8. are those going to the central or nasal half of the left retina. O.D. is the right, and 0.8. the left, eyeball. The rightward half of each is therefore blind; in other words, the right nasal field, R.N.F., and the left temporal field, L.T.F., have become invisible to the subject with the lesion - at Cu. 44 PSYCHOLOGY Fig. 24. Schematic transverse section of the human brain througTi the Rolandic region to show the crossing of motor fibres in the neighbourhood of the medulla. 8., fissure of Sylvius ; CO., corpus callosum; N. C, nucleus caudatus, and N.L., nucleus lenticu- laris of the corpus striatum; O.T., thalamus; C, crus; P., the pons; M, medulla oblongata; VII., the facial nerves passing out from their nucleus in the region of the pons. The fibres passing between O.T. and N.L. constitute the so-called internal capsule. ordinarily the peripheral sensory neurones are in connection mainly with the side of the cortex opposite to that, from which they originate. For example, the touch nerves of the left hand find their cortical terminations in the right side of the hemispheres. The optic nerve, however, affords a curious modification of this plan. The neurones from the right side of each retina are connected with the right side of the brain, those from the left side, with the left hemisphere. (See figure 23.) In this particular, as in some others, the optic tiact is THE PSYCHOPHYSICAL ORGANISM 45 peculiar. The retina itself differs from all the other sense organs in being a part of the brain, which has in the course of development been dislocated from its original position. Cortical Motor Centres. — Another great group of these cortical cells in tlie region marked M, generally known as the region of Rolando, from its proximity to the fissure of that name, is well recognised as being in connection with voluntary muscles, which are controlled from this centre. The volun- tary muscles of each half of the body appear as a rule to be controlled mainly by cells situated in the opposite side of the brain. (See figure 24.) In addition to the Rolandic zone there are small motor areas in other regions of the cortex, notably one for eye move- ments in the occipital region, and no doubt one in the audi- tory region for the control of the ear movements which in man have so far lost usefulness as to have passed almost wholly out of voluntary guidance. In general each area of termination for sensory neurones is in close proximity to a region whence issue motor neurones controlling the muscles that move the part in which the corresponding sense organ is found. This arrangement has been described in the spinal cord. The Eolandic region enjoys its peculiar prestige largely because it governs almost all the important movements of the body, which are executed by muscles controlling regions for which the skin furnishes the sense organs. These senses are represented in the region adjoining the posterior edge of the Eolandic fissure. The arms, hands, body, legs and face all come under this caption and the Eolandic zone is accord- ingly that from which their movements are controlled. This representation of the skin senses at the Eolandic surfaces may account also for the representation there of motor control over areas already represented elsewhere. For example : the eye is not only a retina but also an organ with tactual senses and its cortical motor control is apparently divided between the , occipital region where the retina is represented and the 46 PSYCHOLOGY Eolandic region where the tactual sensory tracts find their cortical termini. Cortical Association Centres. — In view of such facts as we have just been rehearsing, the cerebral cortex has been described as a projection system, representing every sensitive point and every voluntary muscle in the body. There are, however, other large areas in the cortex which are not in immediate control of muscles, nor do they represent the emergence point for neurones in connection with the sense organs.* These centres marked A are called by Flechsig, who has studied them most carefully, association centres. The location of one of these centres, known as the island of Eeil, lying beneath the fissure of Sylvius, although not shown well by our cuts, is indicated in figure 19. Their busi- FiG. 25. Fibres associating the cortical centres with one another. (Schematic, James after Starr.) ness seems to be that of uniting the several sensory regions, sucL as H and V, with one another and with the *Certain authorities question this assertion, especially the lat* ter portion of it. THE PSYCHOPHYSICAL ORGANISM 47 motor region. (Compare figures 19 to 21 and 25.) It appears to be true in a general way that these association centres are relatively larger and more highly developed in those animals possessing most intelligence. There is an- other extremely important connecting mechanism, made up of cortical neu- rones the fibres of which form the corpus callosum (figures 24 and 25), by means of which the two sides of the hemispheres are brought into connection with one another. The hemispheres are also united by other less important bands of fibres, of which we shall not speak. These various devices make it pos- sible for a cortical nervous impulse originating in the stimulation of some sense organ, like the ear, to pass into other cortical regions, like that belonging to vision, and thence out through the Eolandic zone to some muscle, producing, perhaps, a voluntary movement. This is probably what would occur, for example, were we to hear the wordS' ■^^Draw a horse,'' then to think how a horse looks, and then finally to make the appropriate movements of our hands. Both hemispheres would be involved in such activities. These relations and others similar to them are suggested by figure 26,, which is, however, merely diagrammatic. Fig. 26. A is the auditory cen- tre, V the visual, W the writ- ing, and E that for speech. (After James.) 48 PSYCHOLOGY The Cerebral Cortex and Mental Processes: A. Memory and Sensation. — When we contrast the cerebral cortex with the other parts of the nervous . system, with reference to its significance for consciousness, we find that it is in the memory processes that the most conspicuous differences first come to light. If one suffers the destruction of the retinse by' acci- dent or disease, or if the pathways be interrupted anywhere between the retinse and the cortex, one becomes blind, but that may be all. When, however, as occasionally happens, one loses the use of the occipital regions, one may not only become blind, but one's visual memory also is lost. It is not possible to remember how familiar objects look. In slight injuries to the occipital region, as well as in minor injuries to the parietal association areas, objects may be seen without being recognised. So-called word-blindness, or visual aphasia, is caused in this way, the patient being unable to recognise or understand written words. If the injury is confined to one side of the brain the common result is hemianopsia in more or less serious form, i. e., blindness to one-half of the field of view, owing to the destruction of the cortical centres receiving the fibres from the corresponding halves of each retina. It is said that the hemianopsia does not ordinarily affect the fovea, i. e., the central point of clearest vision in each retina. Similarly, when the auditory region is injured, one loses the memory of auditory experiences. If in this case, as frequently happens, the disorder be confined to one side of the brain, and this be the side most highly developed (the left side in right-handed people), one cannot understand what is heard. This disease is known as auditory aphasia. The patient is not deaf, for the less developed and uninjured half of the cortex may serve for the production of vague auditory consciousness, but the associations which words and familiar sounds ordinarily evoke are wholly gone, because these were possessions of the now diseased side. The mental condition is not nalike that of a person hearing an unknown THE PSYCHOPHYSICAL OkviAlNiSM 45 foreign language. He is not deaf to the words, but they mean nothing to him, for they have no associations. Certain cases have been reported which suggest that musical memory may be so specialised in the auditory sensory-motor com- plex upon which it depends, as to be obliterated by cortical lesions which leave the general auditory capacity largely unaffected. B. Motor Control. — A condition closely comparable to sensory aphasia is that of motor aphasia, a disease in which one cannot articulate coherently. One is not necessarily dumb, and there may be no true paralysis of the articulatory muscles. But one simply cannot make the enunciatory move- ments in their correct order. This disorder is often found connected in right-handed persons with diseases of the left side of the motor region of the cerebral cortex, which "is in control of these muscleSo (Compare figure 24.) But it may be brought about — and often is — as a secondary consequence of auditory aphasia. If, when we speak, we are in the habit of having in our minds just prioi to enunciation the auditory- image or thought of how the words are going to sound, any difficulty which prevents our securing these auditory images will effectually check our utterance. ISTow auditory aphasia involves precisely this difficulty in commanding auditory images. As most of us do actually employ auditory thoughts to innervate our speech muscles, for we learn to speak as children by imitating sounds, it is surely not unnatural that auditory aphasia should so often be accompanied by motor aphasia. Cases are on record of persons who employed visual instead of auditory imagery to innervate the speech muscles, and who, upon suffering from lesions in the visual regions of the brain, were seized with motor aphasia. The sensory- motor jarc, or circuit, as we have previously remarked, repre- sents the unit of action, finding no exception in the activity of the complex cortical centres, and any interruption of it la the sensory portion may be as fatal to its proper operation 50 PSYCHOLOGY as a defect in the muscles themselves. This is brought out ui the accompanying diagram, figure 27. Further Formulation of the Facts Described TJnder A and B. — Such facts as these just described indicate to us that memory is in a peculiar way dependent upon the in- tegrity of the cortex. Visual ideas, tactual ideas, auditory ideas, and the like can apparently be recalled only when the several parts of the cortex with which these functions are connected are intact. In the first instance a visual conscious- FlG. 27. 80, a sense organ; SC, a sensory cortical centre; CA, cen- tral association centre; MC, a cortical motor centre; AI, a mus- cle. If M has become accustomed to contracting in response to a stimulus from 80, any interruption of the neural pathway joining the two, whether at 1, or 2, or 3, may destroy the coordination and render M temporarily ineffective. ness involves not only a visual cortex, but also a retina, and more or less of the intermediate organs between the two. A similar thing is true of the relation of all the other sense organs to the various elementary forms of sensory experience, such as touch, sound, taste, etc. But once the sensory ex- perience has occurred, the cortex instantly takes up the im- press and memory becomes possible. Destroy any part of the nervous system save this, and conscious memory may escape destruction. Destroy any specific sensory region in this cerebral cortex, and the corresponding sensory memories are obliterated or seriously deranged. Destroy a region in the motor zone, and the voluntary control of some muscle, or group of muscles, is affected. Destroy or injure the as- sociation centres, and the intelligent conjoining of ideas, impressions, and movements is likely to be impaired. THE PSYCHOPHYSICAL ORGANISM 5 1 The character of the defect seems dependent in a measure on the particular association area injured. Injuries to the frontal lobes are likely to be marked by disorders of attention, concentration and the higher mental and emotional capaci- ties. Injuries to the parietal association centres on the other hand are likely to be distinguished by disturbances in ability to connect ideas and sensations with their proper companions. Things seen, heard and touched fail to call up appropriate ideas and are accordingly improperly understood and inter- preted. Experiments on monkeys seem to show that in those animals at least the frontal lobes play an essential part in learning new acts. So far as it goes, this fact harmonizes with the observations on human beings. Owing to the great individual variation in the development of the different portions of the central nervous system, the gravity and permanency of these psychical disorders brought about in the way suggested, i. e., by destruction of certain areas, varies very greatly under different conditions, so that the statements as made must be understood as attempting to convey only the broad general facts. When it is remembered that our most important and signifi- cant acts of will are based upon hopes and fears and beliefs which involve calling upon the memory of our past expe- rience, one begins to appreciate how immensely important for all our life history this memory function of the cortex must be. Thus we choose, for example, one course of action rather than another, because we remember that somebody will be benefited if we act in this way, or injured if we do not. Memory always operates whenever we deliberate, and anything which would deprive us of memory would effectually destroy the will. The cortex of the cerebral hemispheres as the physiological substrate of conscious memory is thus the unquestioned peer among the various gross structures in the nervous system. The Cerebral Cortex and the Lower Centres. — Experiments 52 PSYCHOLOGY on certain of the lower animalS;, for instance frogs, indicate that with them there is a rather extreme differentiation of function, such that after removal of the higher centres, the lower centres (like the medulla, the cerebellum, and the optic lobes), enjoy an almost complete control over certain special coordinations, one directing the movements made in croak- ing, another those of turning over and still another those of jumping. These m^ovements are carried out with consider- able accuracy in response to appropriate sensory stimulation. On this analogy it is sometimes said that the cerebral cortex of man acts simply as a general overlord receiving informa- tion from the senses and issuing commands to the motor un- derlings who then execute them. This metaphor is accurate enough, if it be not supposed that in man these lower centres are as independent as in the animals. The development of man's nervous system has been accompanied by a certain loss of autonomy and independence in these lower centres which are apparently unable to dispense entirely with the controlling influences of cortical action. Crucial evidence on the matter is difficult to obtain, because man cannot survive the loss of the higher centres. Important Features of Cortical Action. — In concluding this statement, two things should be emphasised. (1) The cortex is nowhere in direct connection with a sense organ, but receives all its sensory stimulations through the inter- mediation of the peripheral neurones and of some of the subcortical groups, like the thalami, the medulla and the olfactory bulb. (The olfactory pathways possess certain peculiarities which cannot be fully described here.) The cortex is similarly in direct connection with no voluntary muscles, but communicates with them by means of the sub- cortical neurones. The shortest possible pathways which could, so far as is now known, be employed in the trans- mission of an auditory or visual stimulus to the cortex, and back from the cortex to voluntary mugeles, is shown in THE PSYCHOPHYSICAL ORGANISM 53 figure 28. The anatomical arrangements peculiar to these illustrative cases may be regarded as typical (save in the case of the olfactory tract; see figures 28 and 29) for all 1 voc Toe R()G 3 AOC TOG A. Mc)C 3 COS Toe M()C COOl Boe ROMG ^^ -^^ >k bJc cJc s^g ooc Ro. I Co. H I C El S soc Ml Fig. 28. Diagram to illustrate the shortest pathways from sensfi organs to cortex, and from cortex to muscles. Taking the skin nerves as an example of the sensory pathways we find, first, an end-organ in the skin, then a cell in the ganglion outside the spinal cord sending a fibre out to the end-organ and another into the cord. [This is the sensory neurone of the func- tional classification, the peripheral neurone of the anatomical classification.] The next neurone has its cell-body in the medulla and communicates with one located in the thalamic region, which in turn communicates with a cell in the cerebral cortex, thus completing the chain from skin to cerebrum. Pass- ing downward from the motor centres we find a long fibre ex- tending through the so-called pyramidal pathway (of which the principal crossed tract is shown in Figure 24) and terminating somewhere in the grey matter of the anterior horn of the spinal cord, where it communicates with another neurone which sends out a fibre to a muscle. [The cell originating in the medullic region in the ascending pathway, together with that in the thalamic region and the descending motor neurone in the spinal cord, belong to the subcortical group of the anatomical classifi- cation and, with the exception of the motor neurone, to the central neurones of the functional classification. The cortical neurones of the anatomical classification also belong to the cen- tral group of the other classification.] A similar arrangement obtains in the case of certain of the muscles of the head, such as the ocular muscles, for example, where, however, the immedi- ately controlling neurones issue not from the spinal cord, but 54 PSYCHOLOGY sense organs and voluntary muscles, but the pathways gener- ally traversed by nervous impulses are probably much more complicated and indirect. (2) The cortex seems always to act in an essentially unitary way. Consciousness is, then, the counterpart of the total mass of shifting tensions going on all over the cortex at any given moment. When this tension is greatest in the occipital region, we are aware of visual qualities. When the temporal convolutions are under greatest strain, conscious- ness is auditory, etc. Moreover, in this picture of conscious- ness as the counterpart of a unified series of physiological tensions all over the cortex, we must not forget that the whole nervous system is in a measure involved. These tensions are of such a character as to require a constant escapement through the motor pathways, with a momentary establish- ment of equilibrium as a consequence of such escapement, and a fresh disturbance of equilibrium as a secondary con- sequence; this latter disturbance being brought about through movements actually executed. Such a recurrent series of movements and sensations, illustrated by the accom- panying diagram, is involved in every coherent, consecutive occupation of which we are capable. (Figure 30.) Sleep from the brain stem. With this explanation and the legend which follows the diagram will be easily understood. 1, the visual tract; 2, the auditory tract; S, a cutaneous tract; 4> an olfactory tract different in character from other sensory paths; 5, a motor tract. Ro. and Co., rods and cones; BG, bipolar retinal cell; RQ, large retinal ganglion; TC, cell body in the thalamic region; VC, cell in the visual cortex of the J occipital region. HG, hair cell of the cochlea; GG, ganglion cell of the cochlea; MG, cell in the medulla oblongata; TG, as in the visual tract; AG, cell in the auditory cortex of the upper tem- poral region. E8, end-organ in the skin; SG, cell of the spinal ganglion on the posterior root of the cord; MG and TG as be- fore; GS, sensory cell in the cortex posterior to the Rolandie region. OG, olfactory sensory cell in upper part of nasal cav- ity; BG, cell in the olfactory bulb; COl, cell in the olfactory cortex of the hippocampal region. RMG, motor cell of the Ro- landic region; 8G, motor cell of the ventral horn of the cord, Bending down a process to M, a muscle. THE PSYCHOPHYSICAL ORGANISM 55 affords practically the only instance of cessation from these coordinated series of stimulations and movements. Idea- tional processes are often, of course, interpolated between Fig. 29. Diagram to illustrate certain features of the con- duction pathways in the nervous system. 8k., a sensory nerve terminating in the skin; 8.G., cell in the spinal ganglion, to which the nerve fibre belongs, sending other fibres inward to the spinal cord, where the connec- tions are made with cells above, with others below and still others at the same general level at which it enters the cord. Cl.C, a cell in Clarke's column by means of which impulses may be sent from the skin to the cerebellum. Med., medulla b - longata, where the numbers 1 and 2 indicate respectively a cell by means of which impulses may be sent to adjoining parts of the brain connected with the neurones of the medulla, and a cell by means of which the impulses may be directly transmitted to the cerebral cortex by way of the thalamus, designated by T. The numbers 1 and 2 in the thalamic region indicate, as in the case of the medulla, a pathway to adjoining structures and a pathway to the cerebral cortex. Elsewhere in the dia- gram the number 1 indicates a neurone for branch connections, e. g., in the spinal cord one is shown joining a sensory neurone to a motor neurone. Cb., the cerebellum, which is shown con- nected with the skin and with the motor neurones, as well as with the cerebral cortex via the thalamus. Other connec- tions of an important character are not represented. Cer., the cerebral cortex. CM., cortical motor neurone; M.N., motor neurone in the ventral horn of the spinal cord; M., the termi- nation of the motor nerve in a muscle. Arrows indicate the direction of impulses. (Modified from Starr.) 56 PSYCHOLOGY the sensation and the movement, as is suggested by the diagram. The Autonomic System. — In addition to the central ner- vous system of which we have thus far spoken must be men- tioned the autonomic system commonly known as the sympa- thetic system;, of which the true sympathetic is a highly important part. The autonomic system, about which our exact knowledge is lamentably defective, is apparently an out- growth of the central system, and the two are intimately con- nected, both as regards their structure and their action. In- deed, certain of the autonomic neurones originate in the central nervous system. The striking peculiarity about the autonomic system, is, as its name indicates, its relatively self- directing or automatic activity. Fig. 30. Diagram to illustrate the progress of a series of coordi- nated movements. S, a sense organ being stimulated; SG, the cortical centre for this special sense; MG, a motor centre con- trolling the muscle, M ; KG, a sensory centre for the kinsesthetic sensation produced by the contraction of M . MGi, another motor centre innervating M^, which in. turn produces the kinsesthetic sensory impulse reported at KGi, etc. ; I, I, ideas or images, whose brain processes may be interpolated anywhere throughout such series, discharging into the motor centre MG2, thus originating a fresh series of movements and kinsesthetic sensations. The autonomic system of neurones may be conveniently, though roughly, described as made up of four great groups. One of these groups consists of a series of ganglia gathered into two long strands extending up and down each side of the THE PSYCHOPHYSICAL ORGANISM 57 spinal cord. This contains the sympathetic system in the narrower and more precise sense of the term. (See figure 13.) The second group consists of the great plexuses of ganglia found respectively in the thoracic, abdominal, and pelvic cavities. The third group consists of plexuses or isolated gan- glia scattered miscellaneously throughout the body, e. g., in the heart, in the alimentary tract, in the walls of the arteries, in the eye cavity, etc. The fourth group consists of neurones originating in the central nervous system but exercising an autonomic function, as in the case of certain cardiac fibres in the vagus, bladder fibres from the sacral region of the cord and the like. These neurone groups are made up of cell-bodies and fibres for the most part unmedullated. By far the greater portion of the impulses which affect their action apparently come from the central system. They certainly discharge impulses into the glands, the unstriped muscles, and, in the case of the heart, into striped muscle. Thus, for example, when an embarrassing announcement is made in our presence a sensory impulse passes over the auditory tract of the central system and thence, among other consequences, impulses are sent to the region in the medulla which controls the sympathetic ganglia connected with the muscular tissue of the blood-vessels, and straightway we find ourselves blushing. The sweat glands may also become active, causing us to perspire. We become aware of the action of these organs controlled by the autonomic system through the sensory im- pulses which they send back to the cerebral cortex. In blushing the face ^Durns/ i. e., the temperature nerves are stimulated and the sensation of warmth results. Similarly, if the heart beat be disturbed, as often occurs in embarrass- ment, sensations of throbbing or of pain are called forth. The general order of events is accordingly this : (1) Stimulation of the autonomic neurones, the original stimulus being either inside or outside the organism; (3) 58 PSYCHOLOGY the consequent activity of muscles or glands reported (3) by sensory impulses aroused either directly (as by the heart) or indirectly (as in the cool sensation from the evaporation of perspiration) by such activity. All the important vegetative and life sustaining processes, such as respiration, circulation, digestion, etc., are under the guidance, partial or entire, of the autonomic nerves. It is consequently to the activity of these parts that we owe our general sense of bodily well-being, as well as our feelings of distress and pain when any of these great life functions go astray. Our consciousness is undoubtedly toned, as it were, all the time by the condition and activity of the organs under the control of the autonomic system. This fact vsdll become very evident when we begin the study of instinct and emotion. The entire nervous system, therefore, and not simply the cen- tral system, is concerned in the modifications of consciousness. CHAPTEE III MIND, NEURAL ACTION AND HABIT It will greatly facilitate our subsequent understanding of the operations of consciousness if we pause to examine at this point some of the things which the nervous system is able to accomplish without the direct assistance of the mind, together with certain general relations of consciousness to neural ac- tion. Such an examination will bring us face to face with one or two of the fundamental principles, or laws, which con- trol neural action. A Matter of Terminology. — Let it be understood once and for all that wherever we speak, as occasionally we do, as though the mind might in a wholly unique manner step in and bring about changes in the action of the nervous system, we are employing a convenient abbreviation of expression which harmonises with the ordinary everyday methods of thinking and speaking about these relations. The real fact appears to be, as we observed in the previous chapter, that whenever we have mental activity, we have also neural activity in the cere- bral cortex. The basal distinction in the two kinds of nervous action to which we are referring in this chapter is, therefore, not primarily between a form in which the mind suddenly produces changes in the nerves as against one in which it does not, but rather a distinction between certain kinds of neural activity overtly involving consciousness, e. g., cortical activity of the cerebrum, and certain other kinds not overtly in- volving it, e. g., spinal cord reflexes. To use on every occasion the long modifying phrases necessary to precise accuracy on 6o PSYCHOLOGY this matter would evidently be unduly cumbrous, and so the commoner modes of expression are employed, but the fundamental facts which lie behind these convenient meta- phors must not be forgotten. Automatic and Reflex Acts. — If we take up the general character of neural action from the genetic point of view, we shall have our attention at once called to the fact that the new-born babe does not come into the world so completely helpless as is sometimes implied. There is a small group of acts which the little stranger is at once able to perform. Respiration, circulation, and digestion are three physiological functions which are carried on from the first. They all in- volve muscular movements, and constitute what are commonly known as automatic acts. The nervous stimulus for such activities is wholly, or in part, within the organism itself. Thus, the chemical condition of the blood may be responsible for changes in circulation and respiration, the presence of food in the stomach incites its digestive processes, etc. We are as a rule under normal conditions entirely unconscious of those automatic activities whose effects terminate inside the organism, although if anything goes wrong with them, they ordinarily cause us pain and thus attract our attention. Other motions can be excited by stimuli outside the organ- ism. Thus the sucking movements necessary for the child to obtain its food may be aroused by touching the lips. The fingers will clasp firmly any object put into them, an act said to be reminiscent of the days when our ancestors lived in trees, and the young had to cling to the branches. Acts of this kind are called reflex. A reflex act, as we re- marked in the previous chapter, is definable as an act in which a movement is made in direct response to a stimulus outside the organism, without the interposition of consciousness. Of course consciousness sometimes takes cognisance of reflex acts, but it does not produce them. We may be conscious that we have winked, and still the closure of the eyelids be due to MIND, NEURAL ACTION AND HABIT 6l a reflex. We are very unlikely not to remark that we have sneezed. Oftentimes, however, reflex acts escape our notice altogether, just as the automatic acts do. Eeflexes which are entirely unconscious, like that of the change in the size of the pupil of the eye, are called physiological reflexes. Those of which we are conscious are called sensation reflexes. They represent the transition from non-conscious physiological processes to fully conscious processes. Sensation reflexes can often be suppressed by conscious processes. A sneeze may be checked by a sufiiciently vigorous resolution, or by introducing some strong diverting sensation like a loud sound. Physiological reflexes are practically independent of conscious control. Were we to observe closely the growth of any child, we should find that from time to time new reflexes were added to his original stock. Thus, winking and sneezing would after a time appear, and finally at about twelve or fourteen years of age the full store of these reflexes as displayed by the adult would be complete. This course of development undoubtedly runs parallel to the development of the several nerve centres and the intercommunicating pathways. 'Now such acts as these, few in number and simple as they are, evidently furnish the child with a nucleus of coordina- tions by means of which to begin the conquering of his world. They are evidently hereditary and, as every normal child possesses them, we may regard them unhesitatingly as racial, or phylogenetic, in nature. The animals generally possess at birth a larger equipment of such inherited coordinations than does man, and certain ones we commonly call instincts. These instincts we shall have occasion to examine with greater detail at a later point in the book, so we may pass them by here vdth the single remark that they are, as regards their origin, undoubtedly akin to the reflexes and the automatic acts. All three are based upon the existence of congenital pathways through the neurones of the nervous system by 62 PSYCHOLOGY means of which stimulations of one or another kind are enabled to produce appropriate responsive movements. They represent thus the outcropping of the universal racial charac- teristics in the individual. Random Spontaneous Movements. — In addition to these relatively well-organised hereditary acts, babies display a great variety of random movements of the muscles of the face, arms and legs made in response to stimulations of every kind. Immediately after birth these movements are com- paratively few and feeble, but they rapidly increase both in variety and force. They are sometimes called spontaneous, because they are evidently too variable and erratic to be re- garded as reflexes. The term spontaneous must not be under- stood to carry any definite implication of will and conscious choice. Undoubtedly to the child himself these acts feel at first much like the true reflexes. The earliest movements of this type simply indicate that the nervous system is so con- structed as to permit neural excitement to escape over various pathways in a random and miscellaneous manner. The or- ganization of these paths so as to produce efficient acts, con- stitutes the process of establishing habits and acquiring volun- tary control of the muscles, of which we shall have much to say. Continuous Nature of Organic Activity.— In the light of the foregoing statements it may, perhaps, arouse no special surprise, although it is certainly a striking fact, that from the moment of birth until death there is never complete quiet throughout the organism. Always do we find muscular move- ments, always something is being done, always activity of some kind is going forward. In sleep itself, which we com- monly associate with complete repose, respiration and circu- lation are occurring, and although each specific muscular contraction is followed by a period of recuperation for that particular muscle, there is never entire quiet throughout the organism as a whole. When awake, these automatic activities MIND, NEURAL ACTION AND HABIT 63 are augmented in the new-born child by such reflexes and random movements as we have mentioned. The reflexes nat- urally occur but infrequently, and as for consciousness, it ap- pears during the first weeks of a child's life only for brief periods, most of the time being devoted to deep sleep. Never- theless, the points at which it does appear are of fundamental importance for our Correct apprehension of its function, and we must examine them with care. The Appearance of Consciousness. — We obtain a significant clue for our undertaking by noticing at what points con- sciousness is most actively at work in adult experience — a matter to which we shall repeatedly refer as we proceed in our study. An illustration may serve to clarify the situation. An expert can use a type-writing machine almost without any conscious guidance of the movements which are necessary to operate it. He has acquired by long practice a set of habits whereby he manipulates the keys. These habits involve, among other things, coordinating the movements of the hand with movements of the eyes, the latter movements being in part reflex, e. g., accommodation of the lens. As the writer pro- ceeds, his mind may be entirely absorbed in the meaning of the sentences which he is composing. But if the machinery of the type-writer becomes clogged, the operator must at once direct his attention to the machine, abandoning all thought of the composition. His automatised writing habits are powerless to deal with such a difficulty and they must consequently give way to conscious control processes. If the facts of this illus- tration be typical of general conditions, as the author believes them to be, it may be asserted that consciousness in one or other of its forms normally appears and participates only in such activities as cannot be efficiently executed by the heredi- tary reflexes and the acquired automatisms. In the light of this conception, suggested by easily ascertainable facts of adult experience, we may interpret the facts of mental de- velopment in infancy, to which we necessarily gain a morg 64 PSYCHOLOGY indirect access. Obviously in the case of the infant there can be at the outset no acquired habits, and it seems reason- able therefore to assume that conscious activities emerge at the point where reflex acts are found inadequate to meet the needs of particular situations. Evidently the equipment of coordinations with which we have found the new-born infant supplied cannot carry him very far in his adjustment to the complex surroundings amid which he finds himself placed. Why he should have been limited by nature to just the special group of inherited co- ordinations which we observe in him is a question for the biologist to answer. We cannot at present go behind the facts. But it is clear at once that in the list of muscular activities over which the babe has control, there is no mention of means for responding very effectively to auditory or visual stimuli, to name no others. If the reflexes and the automatic acts were wholly competent to steer the organism throughout its course, there is no reason to suppose that consciousness would ever put in an appearance. Certainly we never find it obtruding itself where these conditions are observed, except in, pathological instances. The formulation which has been pro- posed is intended to apply primarily in a descriptive way to the circumstances under which mental processes actually come to light in human life. The larger explanatory bearings of the formula as well as its applicability to the fundamental question of the genesis of consciousness in animal life are not under discussion at this point. An Illustration from Hearing. — Let us examine as a typical case what happens when the consciousness of sound first occurs. We know that many children are unable to hear for several days after birth, partly because the middle- ear is filled with mucus. When, however, the ear is able to receive the auditory stimulus, we have at once an excita- tion of the organism for which there is no definite pre-' MIND, NEURAL ACTION AND HABIT 65 formed muscular response. Some children, to be sure, early display a tendency to move the head, as does an adult in localising a sound, and this may possibly be a partially hereditary propensity. But it is problematic whether this ever occurs immediately after birth, and cer- tainly it is quite rare. The usual thing under such conditions is unquestionably the appearance of vague consciousness dominantly of the auditory kind; the stimulation having the tendency, if it be intense, to discharge itself according to the law of "diffusion'^ (of which more anon) throughout many motor channels, involving random movements of the muscles in various parts of the body. Now these movements require coordination. If they are ever to be turned to account, they must be controlled and ordered. The new stimulus has broken rudely in upon the coordinated reflex and automatic activities already going on. It has probably affected the circulation and the respiration. If the child were feeding, it may have shocked him into cessation and, in place of the sucking, set up the unwelcome wail- ing. Such a case is typical of the occasions where conscious- ness comes to light. The organism has end-organs sensitive to sound stimulations, but no ready-made physiological ar- rangements for responding effectively to such stimuli. Con- sequently, when a stimulus of sound bursts in upon its activities, some of which, as we have seen, are always in progress, it finds itself helpless and unable to act in any save a random and disordered way. Straightway appears con- sciousness with its accompanying cortical activities, taking note of the nature of the stimulus and of the various kinds of muscular response which it called forth. From this point on, the development toward the attainment of those fixed and intelligent modes of reaction, which we call habits, is steady and uninterrupted. Were we to take time for a thorough exploration of all the sensory forms of consciousness, e. g., vision, taste, smell, touch 66 PSYCHOLOGY etc., we should find that they are all called forth imder the same conditions of inadequacy on the part of the purely hered- itary physiological mechanisms, of movement, to meet the demand of the physical and social environment. The Formation of Habits. — It shall be our next business to trace in outline the process by which consciousness and the brain bring order out of this threatened chaos and leave the organism a group of habits to which additions are con- tinually made and by means of which the organism becomes increasingly master of the situation. This account will be only a sketch, however, for all the rest of our study will really be devoted to filling in the details. In the chapters upon volition we shall return specifically to these very points. A. Fundamental Facts of Nervous Action. — It will be remembered that in the previous chapter, when studying the nervous system, we observed that in its simplest forms the nervous organism appeared to be little more than a device to connect a sense organ with a muscle and so to enable the discharge of movements in response to stimulation. When we examined complex systems, like that of man, where memory processes are clearly in evidence, we noticed that this same principle was everywhere in evidence, although it gained its expression through the most elaborate arrange- ments in the nervous tissues. We remarked, also, that the normal fate of every incoming sensory stimulus was to find its way out again sooner or later in the form of muscular movements and glandular activities. This tendency is in no way modified by the complexity of the neural structure, ex- cept as regards the ease with which we detect such reappear- ance of the stimulus in the form of motion. If we bear these facts in mind, a considerable part of the mystery seemingly surrounding the processes we are now to investigate will fall away at the outset. B. (1) Excess Movements — The Beginning of Motor Control. — Let us take as a typical instance of the develop- MIND, NEURAL ACTION AND HABIT 6^ cient of motor control the series of events which occur when a baby iirst learns to connect a visual impression with a move- ment of his hand and arm. Suppose a bright, coloured ball is held before his eyes. This stimulus sends strong sensory currents over the optic tracts to the brain centres and some- how or other, as we have seen, these currents must get out again in the form of movements. But we have also seen that there are few or no preformed reflex pathways over which such neural excitement may be effectively discharged. Certainly there are none which enable the child to bring about changes in the stimulus, and this is commonly the important thing. Consequently, instead of some single relatively sim- ple movement like that of reaching, we observe precisely what the principle of "diffusion" postulates as normal, t. e., a mass of aimless, uncoordinated movements in a large number of muscles. The face is wrinkled in a frown or a smile, as the case may be, the fingers open and shut, the arms jerk about, the body and legs move spasmodically and pos- sibly the child cries out. This does not seem a very promis- ing beginning for the development of intelligent control, and yet in point of fact it contains just the features most essential for progress. Speaking generally, we may say that such stimulations call out an excess reaction, a motor response in which are contained, almost without fail, the special small groups of useful and important movements which subsequently become isolated from the general miscellaneous motor matrix in which they at first appear. We can detect the manner in which this result is attained by observing our illustrative baby still further in the light of our knowledge of how we, as adults, acquire new coordinations. Presently, if the stimulus be made more exciting by moving it to and fro, some of these excess movements of the arms will result in the child's hand coming into contact with the ball. We have already noted the hereditary clasping reflex, and we shall not be surprised, then, to find that the tactual 68 PSYCHOLOGY stimulus to the skin of the hand results in the closing of the fingers. Now undoubtedly this first successful grasping of the seen object may be wholly accidental, in the sense that it is wholly unforeseen by the child. He is much more surprised by the occurrence than any of his interested observers, who accredit him with a wealth of conscious purpose and inten- tion of which he is completely innocent. But let us observe what fundamental consequences are bound up with this success. (2) Agreeable and Intense Character of Accidental Successful Movements. — To begin with, the mere shock of surprise and (generally) pleasure makes the connection of the tactual-motor sensations from his hand with the visual sensations from his eye extremely vivid. As he moves his hand, he finds that his visual impressions change. When his hand comes to rest, his visual object also remains quiet. There is no reason to suppose that the child is in any definitely re- flective way aware of these things. He does not say to him- self : "When I see my hand move, I see the ball move; there- fore, the two things are connected in some way.'' Indeed, it is probably impossible for us in adult life to portray ac- curately to ourselves the simple immediacy of such experi- ences as these in infant life. But the important point, after all, is this, that of all the sensations which his whole ac- quaintance with the ball has brought the child up to this point, the ones connected with his seeing it when he grasps it, and his seeing it change when his arm-and-hand-feeling changed, are the ones most intensely connected in his con- sciousness. If we read backward into his mind, then, what we all know about our ovni adult experiences, we may be sure that the child's organism is extremely likely to retain the memory of the highly vivid connection between the visual sensations of the ball and these tactual-motor feelings which accompanied the successful grasping of it. Moreover, the genuineness of this connection is indicated by the evident tendency to MIND, NEURAL ACTION AND HABIT 69 make the successful kind of arm movement, rather than any of the dozens of other movements with which he started his response to the ball, provided we give him at once an oppor- tunity to get again the same visual impression from which he set out. To be sure, many of the irrelevant movements per- sist for a time, but they rapidly become less frequent and finally disappear. The perfect result is of course rarely at- tained without many trials. In this way, however, the child speedily does for himself what nature did in the case of the reflexes, i. e., gives himself a neural pathway through which sensory impulses may flow out over motor channels for the production of effective coordinated muscular movements. In this case we have observed the establishing of a control con- nection between eye and hand. The sight of the ball will henceforth tend to call out the appropriate reaching and grasping movement. (3) The Inhibition of ITseless Movements. — The more firmly this connection becomes established, and the more deeply the pathway is cut between the visual sensory centres and the hand-arm motor centres, the more do the irrel- evant movements of face, legs, and body tend to drop away. They are inhibited, as we say. Probably this inhibition is in largest measure due to the fact that the newly formed channel is increasingly able to carry off all the neural excitation, and in consequence less remains to overflow into other channels. But the result is certainly beyond question, whatever the means by which it is attained. Moreover, just in proportion as any such coordination becomes perfect, consciousness tends to drop out of the supervision altogether, and to turn the process over to the purely physiological mechanisms of the organism. Figure 31 illustrates certain of the relations which have been described. The Attainment and Retention of Modifications in the Hervous System. — The nervous system is not only sensitive to the various forms of stimulation which we call light, 70 PSYCHOLOGY sound, temperature, etc., it also manages in some way or other, as we have already observed, to store up the modi- fications which the stimulations produce in it. These modi- fications which are thus preserved manifest themselves in the disposition of nervous impulses to run in the same channel which predecessors have cut out. If the nervous system were an inanimate mass, we might liken that which occurs to the process by which a path is made across a meadow. The first wayfarer may have selected his special route for any cause HM LM BM.FM Fig. 31. Diagram to illustrate the establishment of motor control through the principle of "excess discharge." VS, visual stimu- lus setting up excitation in the retina, which transmits it to VG, visual centre in the occipital cortex. Thence the neural ex- citement overflows into FG, motor cells controlling muscles of the face, BG, motor cells controlling muscles of the body, LC, motor cells controlling the legs, and HG, motor cells governing the hand and arm. FG, BG, LG, and HG, all discharge into their connected muscles, FM, BM, LM, and HM, and each muscular contraction sets up kinsesthetic sensations, KF, KB, KL, and KH. Of all the movements madejHM alone affects the stimulus VS. VSR represents the stimulus reinforced by being moved by the hand. This intensifying of the factors VG, HG, HM, and the connected factor KH, renders the pathway from V8 through VG, HG, to HM more pervious than any of the other possible pathways. Consequently the tendency gets fixed for VS, or its connected cortical processes VG and KH, to discharge into the appropriate grasping movement, EMH. whatsoever, and his course may have been devious, like those of the cows which are said to have laid out the streets of Boston. But he has left a mark in the downtrodden grass, which the next person to cross the field is likely to follow. Presently the grass is wholly worn away, and thereafter every- one follows the beaten path. MIND, NEURAL ACTION AND HABIT 7 1 The action of nervous impulses is often spoken of as though this kind of thing were precisely what happened. But the moment we recall the fact that the nervous system is part of a living organism, in which processes of nutrition and repair are constantly going forward, and when we remember, further- more, that the organism itself can in large measure decide whether a stimulus shall be experienced again and whether a movement shall be repeated or not, we see that the metaphor of the pathway in the meadow must be abandoned in favour of some idea in which the vital processes of the organism are recognized and the living tissues treated as something other than so much static, plastic clay, which the accidents of the external world can mould to their own exclusive pur- poses. It is undoubtedly true that when avenues, or channels, of nervous activity become once established, they tend ever after to remain and be employed. But the point which we must emphasise is, that the organism itself largely decides which pathways shall in the first instance become thus es- tablished. When one recalls the large number of sense organs on the one hand, and the large number of muscles on the other, between which the central nervous system affords con- nections, it will at once be appreciated that, if the establish- ment of dominant connections in the new-born child were left to the accidents of the first external stimulations and to the vagaries of merely passive nervous centres, the chances would favour the acquirement of insane and harmful habits of reaction. Objects which burn would be just as likely to produce movements of grasping as movements of retreat. We may summarise the general purport of habit as a funda mental principle of nervous action in two propositions. (1) Nervous currents tend to employ those pathways which have been previously established. (2) The organism itself plays a governing part in determining what pathways shall become thus fixed. The Mechanism of Established Habits. — When an habitual 72 ' PSYCHOLOGY coordination becomes thoroughly ingrained, it seems, as we have repeatedly remarked, to become almost reflex and to dis- pense wholly with conscious guidance. A skillful telegrapher can largely abandon over-sight of his hand in sending familiar forms of messages. A musician can play familiar scores while carrying on a conversation. Many of us can write common words although absorbed in some other mental occu- pation. We can walk long distances while deeply engaged in reflection and apparently quite inattentive to the muscular movements we are making. To be sure, it is difficult to prove conclusively that under such circumstances we. are ever abso- lutely oblivious to our muscular activities ; hut to all practical intent we are surely often entirely preoccupied with other things and still are able effectively to carry on habitual acts. A widely accepted account of the mechanism of the process maintains that what occurs is represented hy the following diagram. (Figure 32.) The act — suppose it to be a writing movement — ^is started either by an idea or a sensation. Forth- with, the first' of a chain of 51 s s s Tevelant movements occurs, perhaps in this instance the downward stroke of the pen. This movement is reported by M M M sensations ' from the muscles, ^ „^ joints and tendons of the hand Figure 32. ;i mi, +• and arm. These sensory stimu- lations which in turn instigate succeeding movements, go on till the act is complete, or until the will steps in and stops the performance.' This description is probably roughly correct, but it presents far too simple and diagrammatic a picture to be taken liter- ally. Experiments show that in such cases as writing illus- trates, the sensory cues which are involved come from the eye and even the ear quite as often as from the muscles and joints. They show, too, that ideas, as distinct from sensations, MIND, NEURAL ACTION AND HABIT 73 often play an important part, and that there is the utmost variation from person to person, and in the same person under different conditions, as to what sensory and ideational material is used. But that orderly muscular movements follow imme- diately upon cues which have been organized into these habitual groupings^ that the cues follow promptly upon the previous movement, a.nd furthermore, that the cues are often of an essentially physiological and non-mental character, may be regarded as certain. So far as the diagram indicates these facts it is correct. Results of Habit. — The advantages which accrue from habit are mostly self-evident. When we compare such habitual coordinations as are involved in writing the familiar English script with those employed in writing the German characters with which most of us are far less familiar, we note that the former letters are much more rapidly executed, that they are much more accurately made, and that they produce far less fatigue. It is evident, therefore, that habit is a most valu- able contributor to efficiency in action. Any process which increases speed and accuracy, while at the same time it di- minishes the fatigue of labour, is a possession to be cherished. But more important, if possible, than any of these results is the fact that through the mediation of habits the physiological organism is enabled to cope almost unaided with situations which originally required the assistance of conscious processes, and consciousness is thus left free to go about further attain- ments, which will in their turn become habits and be handec over to certain of the relatively non-conscious processes of the nervous system. Mind is thus ever going on in advance and building up coordinations, which are necessary to the most effective reactions upon the environment. The whole course of mental development could truly enough be described as made up of this process of acquiring habits, which once imbedded in the tissues of the nervous system become the permanent possession of the individual, ready, when need 74 PSYCHOLOGY arises, to step in and deal with the necessities of any particular situation. Moreover, development usually ceases whenever the necessity for further nicety of adaptation to surroundings is no longer definitely felt. This is undoubtedly the reason why various habits settle down on us permanently at certain ages. Many bodily habits, e. g., habits of personal cleanliness, are substantially fixed during childhood, likewise such nervous habits as biting the finger nails. One's manners and standards of dress, one's mode of enunciation and tone of voice are commonly determined during adolescence, as well as one's general moral and religious habits. Professional habits are naturally acquired somewhat later and are ordinarily more mobile than the others mentioned, with the possible exception of the moral and religious group. The lawyer, physician, priest, teacher, bank clerk, book agent and day laborer has each his characteristic gestures, attitudes and habits of thought which mark him distinctly in the eyes of the expert. If we make essential and radical changes In any of these funda- mental habits, it is because of some change in our circum- stances which renders us sensitive to the need for readjust- ment. Innate Hereditary Acts and Acquired Habits. — If we now look back over the ground covered in this chapter, we shall see that consciousness occupies a curious middle-ground be- tween hereditary reflex and automatic activities upon the one hand and acquired habitual activities upon the other. The organism comes into the world with a small capital of these hereditary coordinations. These suffice to meet the most im- mediate and pressing needs in the conservation of life, but they are hopelessly defective for the attainment of anything beyond these immediate necessities. Now and again the world of light and sound and contact breaks in upon the coordinations which our hereditary neural mechanisms are executing, be- cause the adaptive responses made by these mechanisms are MIND, NEURAL ACTION AND HABIT 75 inadequate to the organic necessities of the situation, and at such points we find consciousness appearing. Consciousness immediately enters upon its characteristic cycle. At first of course its activities are vague and crude. But presently we find selected from out the masses of motor responses created by the sensory stimulations to which the sense organs are sensitive, those particular ones which issue in effective mus- cular control over the environment, and straightway we are confronted with habits. As soon as these habits are firmly established, consciousness betakes itself elsewhere to points where habitual accommodatory movements are as yet wanting and needed. It is an interesting fact incidental to this development, that when we attempt to inject consciousness into a process which is either reflex or habitual, we upset the accuracy of the coordination and mutilate its efiiciency. Thus, to direct atten- tion to the act of swallowing, which is a reflex, is to render it for many persons all but impossible of performance. Wit- ness the common difficulty in taking pills. Similiarly, to direct attention to one's mode of walking often results in producing a thoroughly artificial gait quite unlike one's normal manner. The early experiences of appearance before the public, as on the stage, illustrate the point. They also suggest the practi- cal wisdom, if one would avoid embarrassment and fail- ure on such occasions, of concentrating attention as completely as possible on the task in hand, throwing oneself wholly into it, so that there may be no mental energy left over to put on one's own bodily status. Habit and Will. — Although we do not commonly think of it in this way, a moment's reflection will show us that all expression of the will depends upon our ability to command habitual muscular coordinations. For example, I decide after careful consideration that duty bids me refuse a friend's request. ISTow note, that if I speak to my friend, I must fall back upon habits of articulation, which cost me much labour 76 PSYCHOLOGY as a child to attain, but which now largely take care of them- selves. If I decide to write my decision, again I must employ habitual activities, and I cannot by any device communicate intelligibly with my friend without employing these or other similar muscular movements which are essentially habits. Neural habit, therefore, is not only the great emancipator of consciousness from the necessities of endless control over the same trivial round of acts, it is the great tool by which that feature of the mind which we call the will executes its behests and renders our mental decisions and choices effective in the world of action. Without habits, consciousness could never get beyond the borders of the inevitable daily routine. With habit, however, it is able to pass from victory to victory, leaving behind in captivity the special coordinations it needs. Intellectual Habits. — We cannot linger to develop the mat- ter, but it may be helpful simply to point out that the assimi- lation of any subject matter, such as mathematics, for in- stance, involves a precisely similar establishment of habits, which, as the material is thoroughly mastered, are left behind for use when required. We do not ordinarily regard such attainments as concerned in any fundamental manner with muscular movements, although we all recognise readily enough that the sole manner of assuring ourselves a reliable command over a subject matter is to use it, to do something with it. We sometimes think of such doing as purely mental. In reality, however, movements are involved in all cases, and, even were this not true, the general principle of habit, so far as this stands for a law governing the transmission of nervous currents, would still be valid. The gain in rapidity, efficiency, and lessened fatigue would remain, not to mention the freeing of consciousness for further achievements. Apart from such command over special departments of in- formation, what are knovm as '^Tiabits of thought," which we are often vaguely told we ought to cultivate, are in reality largely habits of exercising our attention. We are assured, MIND, NEURAL ACTION AND HABIT 77 for instance, that the pursuit of certain studies is valuable because it will teach us desirable habits of thought. Now when this assurance means anything more than the expression of a pious hope, it refers either to the attainment of a familiar- ity bordering on habit, with a useful field of information, or to the securing of general modes of approaching a new subject matter; habits of alert attention, habits of logical division and persistent search for relations, etc. Whether any special studies are preeminently valuable in the production of this second class of results is a question which can -be answered more judiciously,, if at all, at the end of this book. Meantime, we shall not err seriously if we assert that a wholly fallacious value has often been placed upon so-called formal disciplines, which are supposed to teach us how to do things in general, without any special reference to accomplishing particular results. Ethical Aspects of Habit. — The moment one gets clearly in mind the physiological nature of habit and its basis in the nervous tissues, its ominous significance for morality becomes evident. To break up a bad habit means not only to secure a penitent, reformatory attitude of mind, — this is often easy to achieve, — it means a complete change in certain parts of the nervous system, and this is frequently a thing of utmost diffi- culty of attainment. No amount of good resolution can possibly wipe out at once the influences of nervous habits of long standing, and if these habits be pernicious, the slavery of the victim is sure to be pitiable and likely to be permanent. On the other hand, the momentous significance for the indi- vidual and society of deeply imbedded habits of a moral kind cannot be overestimated. The existence of such habits means stability, reliability, and a promise of the utmost possible confidence. It is all but impossible for one to break over the moral habits of a lifetime. One m.ay at times be mildly tempted by the possibilities such breaches hold out, but actual violation in overt action is essentially impossible. The man 78 PSyCHOLOCS who has been vicious all his life is hardly free to become virtuous, and the virtuous man is in a kind of bondage to righteousness. What one of us could go out upon the street and murder the first person we met ? Such action is literally impossible for us, so long as we retain our sanity. In view of these considerations, no one can over-estimate the ethical importance of habit. To make of the body, in which our habits are conserved, a friend and ally and not an enemy, is an ideal which should be strenuously and intelli- gently held out to every young person. One never can say at what precise moment it may become literally impossible to shake off a bad habit. But we know with perfect certainty that our nervous tissues are storing up every day the results of our actions, and the time is, therefore, sure to come when no amount of merely pious intention can redeem us from the penalty of our folly. Meantime, for one who has fallen under the sway of a habit from which he wishes to escape, this general advice may be given : begin the new regime at once, do not wait for a convenient season. If the result be not likely to be physically disastrous, stop wholly, do not taper off. Give yourself surroundings which will offer the least possible temptation. Do not try merely to suppress the bad habit. If possible, put something else which is good in place of it. See to it that you are always occupied in some proper way until you feel sure that the grip of the bad habit is loosened. It is to be frankly admitted that viewed in a broad way the benefits of habit have their limitation. If the world always did things just as they have been done in the past our civilisation would approach that of the Chinese. But the changes which by the consensus of intelligent persons are beneficial to mankind, the alterations of habit which are progressive, are rarely such as have to do with those purely personal forms of action whose perversion constitutes the most flagrant form of vice. Moral progress always consists in a harmonised action of MIND, NEURAL ACTION AND HABIT 79 wider and wider interests, the securing of broader and truer visions of life. Such progress, while it may change old and accepted habits of life, does not for a moment involve any departure from those rules of personal honesty, sobriety, and chastity which the world's history has demonstrated again and again to be foundations of all sane, happy, human life. CHAPTEE IV ATTENTION, DISCEIMINATION, AND ASSOCIATION I. ATTENTION" Consciousness and Attention. — ^^^''e announced our purpose at the outset to adopt a biological point of view in our psy- chological study, and to attempt at every step to see just how the mind aids in the adjustment of the human being to the environment. If we turn from the merely general statement that the fundamental function of consciousness is to better such adaptive activities, and observe any specific instances of the process of adaptation itself, we shall always find that the actual work of accommodation is going on at the point which we call the point of attention. Attention, we shall accordingly discover, represents the very heart of conscious activity, its most important centre of vitality. It therefore deserves our careful notice. In a vague fashion we all recognize this rudimentary sig- nificance of attention. Thus we speak of the awakening of the new-born infant's mind when we first see signs that the child is attending to something. Moreover, we roughly measure the growth of children in intellectual maturity and power by their increasing ability to give prolonged attention to definite trains of thought. Alienists and specialists in ner- vous disorders inform us that mental disease is commonly accompanied by disturbance in the power of attention. In §ome forms of neurasthenia the attention is extremely un- ATTENTION 8 1 stable and irritable, flitting from one subject to another with feverish haste. In mania there is often a similar, but much exaggerated, attention to the flow of disconnected ideas. In melancholia, on the other hand, as in the milder types of neurasthenic hypochondria, attention is morbidly fascinated by some single idea, or group of ideas, and cannot be long lured away to the normal business of life. Definition of Attention. — When we attempt a definition of attention we experience the same sort of difficulty which we met in defining consciousness, and for a similar reason. So long as we are conscious at all, attention in some degree is present. We therefore find it difiicult to define it without employing the thing itself in the definition. Because of this fact, attention has been commonly referred to as a 'general, or universal, characteristic of consciousness,' or as a 'general attitude,' especially as an attitude of expectancy. In default of a wholly satisfactory definition of attention, we may at least illustrate what we mean by the term. When we look at a printed page there is always some one portion of it, per- haps a word, which we see more clearly than we do the rest; and out beyond the margin of the page we are still conscious of objects which we see only in a very imperfect way. The field of consciousness is apparently like this visual field. There is always a central point of which we are momentarily more vividly conscious than of anything else. Fading gradually away from this point into vaguer and vaguer consciousness, is a margin of objects, or ideas, of which we are aware in a sort of mental indirect vision. This fact that consciousness al- ways has a focal point, which reveals the momentary activity of the mind, is what is meant hy the fact of attention, so far as it can be described in terms of the content of conscious- ness. Baldwin has suggested the accompanying diagram- matic presentation of the facts we are speaking of, in con- nection with certain others. (Figure 33.) The margin of mental processes, outside the focal point of attention, con- 82 PSYCHOLOGY I stitntes what James calls the "fringe of consciousness." Whether we are attending to objects in the world about us, or to ideas in our own minds, there is always such a fringe, partly made up of sensations, partly of ideas. Ko matter what we are especially attending to, we are never completely oblivious to all other sensory and ideational processes. Sensations and thoughts to which we attend commonly occupy con- sciousness longer and more steadily and are ordinarily clearer and more intense than the remainder of the field. Thus, if we give our definite attention to a musical note we re- mark its exact quality much more perfectly than when we simply listen to it in a casual way. It is apt to seem more intense, and it cer- tainly tends to linger longer in the mind. Statements of this kind bring out the fact that we use the term attention at times as virtually synonymous with mental activity, and it is this point of view which Justifies us in speaking of directing the attention to an object or to any part of the field of conscious- ness. To turn the attention to an object is simply to direct one's mental activity toward it. Now, our mental activity, considered as directive, is com- monly called conation, and we must accordingly conclude that attention is a rudimentary form of conation, or tuill. This is unquestionably true. We see, then, that attention is capable of being considered in two different ways. We may emphasise the mere fact of Fig. 33. Graphic repre- sentation of the field of consciousness. 1, the unconscious (phys- iological) ; 2, the sub- conscious, by many psychologists not dis- tinguished from 1; 3, diffused, vague con- sciousness; Jf, more act- ive and distinct con- sciousness, often not distinguished from 5, the focal point of at- tention. The several zones shade into one another and are by no means sharply sepa- rated, as the lines of the diagram unfortu- nately suggest. ( Af- ter Baldwin.) ATTENTION 83 mental activity, illustrated by all attending ; or we may dwell upon the structure of any moment of such attentive con- sciousness, and note the fact of its containing a focal point, with a fading margin. But our emphasis upon one or other of these phases of attention does not alter the fact that the mental process, which we describe in these two ways, is one and the same. In the remainder of the chapter we shall therefore make no attempt rigidly to dissever these aspects of every act of attention, although we shall be frankly most interested in attention as an instance of mental activity. Meanwhile, the best practical definition of attention is afforded by such an analysis and description of it as is contained in the remainder of this chapter. Selective Activities Disclosed in "^ Attention. — Probably the most striking characteristic of acts of attention is their selective nature, and the significance of this function will grow more conspicuous as we examine the facts. We have seen that the nervous system is so constituted that by means of its sense organs it is capable of being affected by various forms of motion in the physical world, e. g., light, heat, sound, etc. This fact has itself sometimes been regarded as a form of cosmic, or organic selection. Thus, of all the rates of vibration in the physical world, the normal retina responds only to those between the' limits of approximately 440 trillions and 790 trillions per second. In a similar way the ear selects a certain group of sound vibrations, and so on for the other senses. Undoubtedly there are many forms of vibrations in the physical world to which we are either partially or wholly insensitive, because we have no sense organs appropriately attuned to their special rates, and are thus incapable of receiving them. The X-ray and magnetic currents afford illustrations of such physical phenomena. However all this may be, it is easy to convince oneself that innumerable stimulations of the kind to which we are sen- sitive are always falling upon the sense organs; and were we 84 PSYCHOLOGY conscious of all of them at once our minds would present a curious conglomerate. As a matter of fact, only a few of these stimuli ever succeed in producing simultaneously that form of cortical reaction which accompanies consciousness, and consequently we are never at any one moment aware of more than a small part of them. Apparently the psycho- physical organism selects from the wide range of potential objects those special ones which shall receive attention and so come to consciousness. Thus, when reading an entertain- ing book we may become altogether oblivious to the rattling of carts in the street, to the odour of the smoking lamp, to the contact sensations from our clothing, etc. Similarly, when we are preoccupied with some train of thought, our atten- tion dwells upon this idea, and turns away from that, accord- ing as the one or the other appears to the mind to be relevant and useful for the business in hand. One and the same physical object may be attended to in various ways, so that it becomes mentally several different objects. For instance, the top of my desk is one thing when I give it my attention in the search for a mislaid paper. It is quite another thing when I attend to it in order to determine of what wood it is made, and it changes once again if I attend to it to dis- cover whether it can be moved through a certain narrow door. Indeed, were it not for the- selective activities exercised in the form of reasoning, it is clear that we could never make any consistent mental advance, but that we should always be at the mercy of our sporadic ideas. We can, perhaps, examine this selective function of attention to best advantage by analysing the principal forms in which attention is found to operate. Forms of Attention. — Probably the most fundamental division of attentive processes, and certainly one of the oldest, is that into active and passive, or, as they are better termed, voluntary and involuntary attention. A more satis- factory division, which we shall adopt, adds one more class, ATTENTION 8$ and recognises (A) voluntary, (B) non-voluntary, or spon- taneous, and (C) involuntary attention. A. Voluntary Attention. — Active, or voluntary, attention is precisely what the name implies, attention as the result of definitely self-initiated activity. In its clearest and most unambiguous form it always involves mental strain and effort. Whenever we attend to anything because we explic- itly will to, we are exercising voluntary attention. It mat- ters not what the object may be to which our minds are thus directed. It may be a sound or an odour, an object which we see, or an object which we touch ; a thought in the mind itself, a memory, an emotion, or anything one pleases. So long as it is attended to, as the result of our definite purpose to give it attention, it must be regarded as involving a case of volun- tary attention. ' That we are capable, within certain limits, of thus direct- ing our mental activity wherever we will is one of the easiest of facts to verify introspectively. Probably the reader has found repeated occasion, before reaching the present point in this book, to make just such voluntary efforts of attention to prevent his mind from wandering off to more attractive by-paths. Obviously the selective function upon which we have already insisted so strongly, is conspicuously in evidence in active attention. Moreover, it seems probable that this type of attention, involving, as it does, the purpose- ful direction of our thoughts, would in its fully developed form be a somewhat later achievement than the other forms, which require for their existence far less of experience. To direct one's thought involves the possession of purposes and plans, however rudimentary, and these are the outgrowth of experience and relative maturity. Young infants are hardly capable of voluntary attention in any proper sense, although they ma}' achieve both non-voluntary and involun- tary attention from the beginning. B. Non-Voluntary Attention. — It requires no extended 86 PSYCHOLOGY reflection upoii our everyday experience to reveal to us the fact that in the course of every twenty-four hours we attend in an effortless way to a great many things to which we have no explicit purpose to direct our thought, to which we cannot, therefore, be said to attend voluntarily in the full sense of the word; but to which we certainly are not attending against our will and in spite of ourselves. Such cases constitute what is meant by non-voluntary, or spontaneous, attention. A few illustrations may make the distinction clearer. It happens not infrequently, for example, that we suddenly arouse to consciousness of the fact that for several minutes our minds have been running off on subjects quite discon- nected from the special occupation with which we may at the moment be engaged. We have "lost ourselves,'^ as we say, in some day dream, perhaps. Our prolonged attention to a subject which sincerely interests us is often of this same character. Our attention is not given as the result of any effort on our part. Eather should we find that it required effort to direct our attention elsewhere. It necessitates no strenuous act of will for the boy interested in athletics to give his attention to a newspaper account of a football game. On the contrary, his attention can only be obtained for less ex- citing themes by some artifice on your part, or by a self- sacrificing effort of volition upon his. The attempt has often been made to specify the objects to which we naturally attend in this spontaneous way. Other things equal we seem to attend by preference to intense stimu- lations, to objects which produce pleasure, to moving things, to persons and animals, and in general to everything which elicits emotion. Such a list has, however, little more than a rough suggestive value. It requires to be qualified in many important particulars before it can be accepted unequivocally. So far as these cases of non-voluntary attention reflect the actual nature of our interests, they must be regarded as afford- ing peculiarly intimate information of the real character of ATTENTION 87 our minds, and so of our wills. They are tlms, in this par- ticular, closely related to voluntary attention. After all, what I am interested in is a very close synonym for what mentally and morally I am. C. Involuntary Attention. — However genuinely voluntary and non-voluntary attention may differ from one another, they neither of them involve attention given against the will. But there are numerous cases in which, at first sight, anyhow, this form of attention apparently occurs ; and it is to this that the name "involuntary attention'' has been given. Thus, for example, if the door slams while I am writing this sentence, I am seemingly obliged to hear 4he sound, however much I might prefer not to do so. To be sure, if I am sufficiently preoccupied a very loud noise may in this way escape my notice; and the obliviousness to ordinary sounds, such as the ringing of the dinner-bell, the striking of the clock, etc., of persons thus engrossed in some interesting occupation is too familiar to require comment. Even severe wounds may under such conditions go unnoticed. Archimedes, absorbed in his studies and unconscious of the sacking of Syracuse, is the classical illustration of this kind of thing. But despite the fact that when one is thoroughly immersed in some congenial undertaking one becomes relatively insen- sitive to sensory stimuli, which otherwise would be noticed, the further fact obstinately remains that even under such conditions stimuli of sufficient intensity will force themselves into consciousness. Certainly we should all agree that in this way bright flashes of light, loud sounds, unpleasant odours, etc., repeatedly intrude themselves upon our attention dis- tinctly against our wills. Moreover, there are experiences in which ideas, instead of sense impressions, thus force them- selves in upon our attention against our wills. What are known as insistent ideas are of this character. The hypo- chondriac, for instance, is unable long to keep his attention away from his own bodily ailments, real or fancied. He may 88 PSYCHOLOGY make a sincere effort to divert his mind, but in spite of him- self the unwelcome idea presently shows its face at the door and claims his recognition. Less definitely morbid than such cases, and still illustrative of the imperious command exercised at times over our at- tention by certain ideas, are the intense experiences of the emotional kind. Great joy, great grief, great anxiety, brook no prolonged opposition. We may attempt to force our at- tention on to the lines of the day's work and for a moment succeed, only to find ourselves in the next moment once more mastered by the idea we had attempted to put behind us. Certain psychologists would prefer not to give the name in- voluntary attention to these cases of attention against the will to ideas. But they are clearly more closely related to this form of attention, as illustrated by our forced attention to intense sensory excitation, than they are to the other classes we have distinguished; and we shall accordingly designate them as cases of involuntary attention. Interrelations of the Forms of Attention. — We have al- ready intimated that involuntary and non-voluntary, or spon- tanvX)us, attention are genetically prior to voluntary attention. Undoubtedly the earliest experiences of a baby involve in largest measure spontaneous attention to sensory stimuli. The rude power with which some of these stimulations force themselves on the child's notice might give ground for the postulation of involuntary attention also. But if we confine the term '^involuntary attention" strictly to such cases as those in which we attend against our wills, it is doubtful whether we ought often to apply the designation to a young child's at- tention; for we can hardly speak with confidence of the new- bom child's possessing any resolution not to attend to a given stimulus. Spontaneous attention, then, worhing in the main upon the sensory material supplied by the physical surround- ings, constitutes probably the earliest and most fundamental type of attention process. ATTENTION 89 (1) Voluntary attention is apparently a derivative form of spontaneous attention, which may arise as soon as, and when- ever, there is a tendency to the splitting of attention, a felt tendency to opposition against the direction our attentive energies are taking. Evidently this can only occur when we have developed intellectually to a suflficient degree to set over against some momentary disposition, or action, a more or less definitely formed plan involving interests and purposes op- posed to the present activities. When we say that in volun- tary attention we force ourselves to attend to some particular object or idea, what we evidently mean is, that the mind in its entirety is brought to bear in suppressing certain disturbing objects or ideas, and in bringing to the front the chosen ones. The act of voluntary attention is, in short, an expression of the sovereignty of the whole mind over its lesser parts, i. e., over the disturbing or alluring ideas and sensations. (2) As has been already pointed out, spontaneous, or non-voluntary, attention is likewise in reality just such an expression of our total mental organisation at the moment. Those things to which we spontaneously attend are the things to which our minds, by virtue of their temporary condition, inevitably go out. And if we took into account the entirety of these spontaneous acts of our attention for any considerable period of time, we should undoubtedly secure an extremely accurate portrait of the real constitution of our minds. In the sense, therefore, upon which we commented briefly in an earlier paragraph of the chapter, non-voluntary attention is itself an expression of the individuality of the mind, and thus an expression of the true source of our volitional acts. It is a sort of voluntary attention, in which there is no internal, mental opposition to be overcome, and from which we are consequently apt to feel one characteristic fact of com- plete volition has been subtracted. External obstacles are of course repeatedly encountered and mastered in this form of mental activity. It appears, then, that the distinction be- QO PSYCHOLOGY tween volmitary and non- voluntary attention is not absolute, in the sense that we can always determine without question to which class a specific case of attention belongs. Quite the contrary. It appears that there is a gradual transition from one class to the other, through cases which partake of the characteristics of both forms. Thus, for example, we should have to admit the existence of many cases in which it would be all but impossible to say whether we were attending to certain subjects as the result of a definite purpose and an explicit effort to attend, or as the result of more or less unconscious mental drifting. "What shall one say, for instance, of the attention which is given to the routine duties of daily life? Some of them undoubtedly require definite, purposeful attention. Others enlist our spontaneous interest, require no effort and reveal little or no antecedent purpose to attend. Many others are surely on the border line, where it is not easy to say whether our attention is altogether due to spontaneous interest or to preconceived purpose. Meantime, we must admit that it is in voluntary attention that consciousness raises the human being into the greatest freedom from mere routine, with the greatest inde- pendence from mere temporary surroundings. (3) The true relation of involuntary attention to volun- tary and non-volimtary attention can hardly be understood without reference to the psychophysical organism as a whole. But fortunately we have all along taken this into account, and our present mention of it will mark no change in our point of view. So far as concerns such instances as those in which we are forced against our will, or at all events without our mental consent, to notice intense sensations, it would seem that in- voluntary attention must be fundamentally opposed to volun- tary attention at least, whatever might prove to be the case as regards non-voluntary attention. The one form of atten- tion expresses the will, the other either defies, or disregards. ATTENTION 9 1 the will. Such differences certainly appear to be funda- mental; but we shall see reason to modify this view, when we consider that both forms of attention are vital functions which are brought out and developed in the general adaptive reaction of the organism to its social and physical surround- ings. If we remember that those objects which are harmful to us commonly stimulate the nerves very violently, we shall begin to see how in the general economy of the organism it may be useful to have our senses so constructed that they shall call our attention to such possible sources of danger as are represented by these intense stimuli, even when we do not consciously desire to have our quiet thus invaded. We shall begin to see that in the interests of the continuation of life and health it may be desirable that loud sounds and extreme temperatures, intense lights and violent odours, should have the power to elicit the attentive reactions from us, just as do the pains of over-fatigue and of diseased conditions of our bodily organs. In a sense, therefore, such reactions are instances of a kind of organic selection from among various movements of just those which shall result in our making momentary accommodation to the invading stimulus. If it prove really menacing, we may then take to flight, or adopt such other precautionary measures as the situation demands. If it be, in point of fact, innocuous or insignificant, our minds are left free to revert to the interrupted occupation. Involuntary attention of this kind represents, accordingly, the protest of the primarily physiological portion of the organism against a too complete subserviency to merely in- tellectual conscious processes. Involuntary attention is only involuntary when the mind is viewed in isolation from the body. It is a kind of spon- taneous bodily attention, and it is undoubtedly selective in a true enough sense. Moreover, even when viewed from the mental side alone, such attention could only properly be called involuntary, never passive. The term passive is quite mis- 92 PSYCHOLOGY leading. Involuntary attention, once it is aroused, is just as genuinely a form of mental activity as is voluntary attention. Its antecedents, both mental and physical, are in part different and often its consequences are different too. But both opera- tions are mental acts, and neither of them can properly be designated in terms of pure passivity. Summarising Statement on the Forms of Attention. — In all forms of attention, then, we find selective activity revealed. Selection always implies a purposive, forward- looking type of action, and this is precisely what attention is in all its forms. It stands for the fact that the organism is teleological in its very constitution. That is to say, the organism contains within itself certain ends to be attained in course of development by adjustive activities. In part these ends exist imbedded in the physiological mechanisms, where they come to light as reflex, automatic, and instinc- tive acts, sometimes accompanied by consciousness; and in part they exist as conscious purposes, in which case they appear as recognised intentions. In spontaneous and volun- tary attention the psychological antecedents of the act are more conspicuous, in involuntary attention the physiological antecedents are more prominent. All three forms, however, involve as a matter of course both neural and psychical factors. Figure 34 indicates the genetic relations of the three forms of attention. SPONTANEOUS ATTENTION INVOLUNTARY VOLUNTARY Fig. 34. Showing genetic relations of forms of attention. Duration of Attention. — It is extremely difficult to secure reliable information as to the length of time we can and do attend to objects in non- voluntary and involuntary attention, for the conditions m these forms of attention are necessarily ATTENTION 93 rery unfavourable to accurate introspection. But having dis- covered that the differences among the several forms of atten- tion are relative and not absolute, we may, perhaps, safely assume that the facts which we find in voluntary attention are fairly representative of the other forms, and these facts are fortunately rather easy to make out. All voluntary atten- tion displays a more or less rhythmic pulse, the duration of which varies considerably under different conditions. If we attempt to attend to a letter on this page, we shall find that we can only do this for a moment or two, unless we constantly observe something new about it. Otherwise we invariably find, either that the eye has moved away to something else, or that the mind has wandered off on to an entirely different subject. However constant the physical object may remain, to which we thus attend, we can only continue our attention to it provided we continually see it in some fresh fashion; provided, that is to say, that the mental object keeps changing. This seems to be a fundamental law of our mental life, and did space permit we might profitably enlarge at some length upon its implication. A few consequences we may properly pause to mention. A. Consequences of Change in the Focus of Attention. — Evidently change is the primal law of mental life, as well as of bodily life. Thought processes which cease to move, cease to exist. They simply go out. To keep a thought alive we must keep turning it over, keep doing something with it. Mental paralysis is mental death. It is a familiar experience with all of us, especially with students, that occasionally when a question is asked us our minds either become perfectly blank, or remain for a moment stupidly confronting the mere sound of the words addressed to us. In such a case the only salva- tion lies in doing something, doing almost anything is better than such quiescence. Often to begin speaking is sufficient to break the spell, however pointless our remarks may be. The act of speech starts up the cerebral machinery and presently, 54 PSYCHOLOGY if we keep our composure, we get our thought once more in movement. Similarly, the boy told to think about what he is studying finds himself, in the effort to execute the injunction laid upon him, simply surveying the page before him with an apathetic gaze. He is merely exposing himself innocu- ously to the light waves proceeding from the page. Mentally he is either in a condition of partial asphyxiation, or his mind is off engaged upon something really of interest to him. He is not in any proper sense attending to the subject matter of his work at all. For such a youth the sole possibility of progress consists in taking the topic and forcing himself to turn it over, ask questions of it, examine it from new sides. Presently, even though such questions and inspections be very foolishly conceived, the subject will start into life, will begin to connect itself with things he already knows, will take its place in the general furniture of his mind ; and, if he takes the next and all but indispensable step,_ and actually puts his rudimentary information to some use, applies it to some prac- tical problem, incorporates it, perhaps, in an essay, or even talks about it with others, he will find he has acquired a real mental tool which he can use, and not simply a dead load which must be carried on his already aching back. What we call attending to a topic for a considerable period of time will, therefore, always be found to consist in attend- ing to changing phases of the subject, to ideas associated with it. Thus, to fix one's mind upon history for an hour or two will involve attending to hundreds of thoughts about the special historical subject, or problem, with which we are concerned. Accordingly, these instances of the practical con- tinuation of attention to a single subject strongly confirm our position, instead of contradicting it, as might seem at first sight to be the case. B. Why Attention Shifts. — It has been suggested that the rapid changes of attention are due primarily to fatigue in the delicate cortical cells which are connected with conscious proc- ATTENTION 95 esses. Whether this statement be accepted or not, we gain a very significant suggestion in explanation of these changes, when we remember what the essential function of attention appears to be. We remarked at the outset that attention is simply a name for the operation of the central, and most active, portion of the field of consciousness. We have all along maintained that the real business of consciousness is to be sought amid the adaptive responses of the organism to its life conditions. We have also pointed out that, if this concep- tion be true at all, it is at the point of attention that we shall find the most obvious and important part of the adjusting activity in progress. Now, in the nature of the case, each particular act of adjustment must be of relatively brief dura- tion. In the case of common objects in the world of sensa- tions it consists as a rule merely in the recognition of the stimulus {e. g., as a colour, as a sound, as a book, or a word, etc.), with a motor response, wjiich consists, perhaps, in some movement of the eyes or head calculated either to bring to notice some new and useful phase of the stimulus, or to divert further attention altogether away from it. Thus we look, for instance, at a book, recognize it as the one for which we are searching, pick it up and proceed to examine it; in this way continuing the activity of attending to the book, but, as a matter of fact, continuing it in the form of attention to ever new features. The same sort of thing is true when our atten- tion is occupied with ideas, instead of with sensations. In short, so far as attention is really an activity of the relating, adjusting kind, its work is done when the relation between the mind and the thing attended to is once established. This is the mental, as distinct from the physiological, part of the adjustment; and attention must go elsewhere, because it is intrinsically the adjusting act itself, and other things are demanding of the organism the same energies of adjustment. To retain our attention for any considerable period an object must, therefore, by changing its aspect, present itself as a new 96 PSYCHOLOGY object, to which fresh responses can be made. No doubt we find here the reason why painful objects are so imperious in their monopoly of our attention. They demand an adjust- ment which we are often unable to make successfully and attention consequently recurs to them again and again. Kange, or Scope, of Attention, — The question is often asked : How many things can we attend to at once ? Various answers have been given, some authorities maintaining that we can attend only to one object at a time, others insisting that we may attend to an indefinite number. We must sharply distinguish between the question in the form in which we have given it, and the question often, but erroneously, treated as synonymous with it, i. e., How many things can we do at one time? We have seen in the preceding chapter that there is literally no limit to the number of things we can learn to do at once. It is, in this latter case, simply a question of how elaborate we can make our .habitual motor activities. A skilled pianist, or a trained acrobat, may do dozens of things simultaneously. But the question of how many things we can attend to is much more puzzling. The differences of opinion upon the matter are, however, apparently due in the main to a failure to define with pre- cision the underlying mental conditions. It is the view here adopted, that we never have more than one mental object before the mind at any one moment. This object may be complex, or simple, but if it is really present in its entirety to consciousness, it is cognised mentally as a single thing. To illustrate, we may take the case of perceiving a table. If we examine introspectively the manner in which we are con- scious of such an object, when we allow the eyes to rest mo- mentarily upon it, we find that we perceive it as a complex single object; not as four legs, plus a top, plus a colour, plus a particular shape, etc. N"ow, these characteristics of a table which we have mentioned all correspond to distinguishable parts of it, and we might speak in a certain sense of having ATTENTION 97 attended to all these circumstances at once. But this ■would be an injudicious mode of expression, tending to confuse oui ability to analyse the physical object, or our own conscious- ness of the object, with the fact of the manner in which we actually perceived it in our momentary glance. However many things, therefore, may be present to us at one moment, it seems probable that our consciousness is of all of them as a single mental object, which we may, nevertheless, imme- diately recognise as being complex in its constitution, mean- ing, and references. Indeed, we may go further, and say that in order to perceive an object as one, there must be some com- plexity in it, which we thus synthesise into a unit. A pure, undifferentiated conscious quality never does, and apparently never can, constitute the object of a cognising consciousness. Plurality is, in short, just as necessary for an object of atten- tion as unity; but our mental activity always gives the stamp of unification to these plural particulars. How many such particulars can be brought together in any one act of con- sciousness is a practical problem for experimental psychology. The various interesting experiments which have been per- formed to test the so-called scope of momentary consciousness must all be interpreted in the light of the foregoing consid- erations. Thus, we find that with momentary exposure we can cognise visually four or five letters, under proper condi- tions. When the letters make words the number which we can cognise in this instantaneous fashion quickly rises. It is possible to make the exposure time so short that we cannot perceive anything with certainty. As the duration of the exposure is lengthened, we soon reach a point where we can feel our attention rapidly shifting to take in serially two or more groups of the letters or words. Similar experiments have been made with sensations other than those of vision with results differing in detail but similar in the principles involved. To these facts we shall revert in another chapter. Some sensations, which have become thoroughly dissociated gS PSYCHOLOGY from one another, seemingly refuse to come together at all into simultaneous objects. Thus, experiments have been made which render it altogether problematic whether we can attend to a sound and a colour simultaneously. We hear the sound and then the attention oscillates to the colour, or vice versa. The same thing is true of sensations of contact, when con- joined with either sound or colour. On the other hand, fusions of two kinds of sensations, like those of taste and smell, are of course always attended to as simultaneous. They are not sensed as two. Inattention and Scattered, or Dispersed, Attention. — Inat- tention is often spoken of as though it were a positive mental condition, just like attention. As a matter of fact inattention to any subject simply means attention to some other subject. In school-children of various ages this condition is often exasperating to the last degree. Its cause, however, is not the absolute loss of attention, but the direction of it into some forbidden but attractive channel. Wandering, or sporadic, attention also is never, properly speaking, the negative of attention. It is simply the unstable, flitting, inefficient form of it. This condition is sometimes spoken of as scattered attention, and, when not due to actual mental disease, is cer- tainly attributable, if long continued, to bad mental surround- ings, i. e., surroundings which neither encourage nor give scope for the expression of native and normal interests. It is proper enough to speak of the marginal part of the field of consciousness and of the unemphasized aspects of the focal part as belonging to the region of inattention, but such ex- pressions must be understood as marking differences of de- gree in attentiveness, not a radical distinction in the kind of process concerned. Dispersed attention is another much abused term. To have one's attention completely dispersed would be to become unconscious. The conditions properly describable by this term are illustrated in the general lowering of our mental ATTENTION 99 alertness when we become drowsy. Mental distinctions of all kinds tend, under such circumstances, to become blurred and indefinite. The state is one of fading attention. Never- theless, as long as we are conscious at all, we are always more clearly aware of some part of the field of thought than we are of the remainder. Our attention is never distributed evenly over the whole of the conscious field. If it ever were thus distributed, completely dispersed attention would, indeed, be realised. Motor Accompaniments of Attention. — It will be remem- bered that in our account of the nervous system we mentioned the existence of evidence tending to show the importance of the association areas of the frontal lobes for the higher forms of mental process involving concentration of attention. In our description of attention thus far, we have also made occasional reference to the part played by sense organs and brain; but this has been somewhat incidental, and we have hardly noticed at all the conspicuous position of muscular activities. To bring out the significant facts bearing on these matters it will be convenient to avail ourselves temporarily of another common classification of attentive processes, dif- fering from that which we have employed. This is the division of attention as sensory, or ideational; a division which certain of our illustrations have involved. All atten- tion to objects stimulating the sense organs, every process, therefore, of sensation and perception, involves sensory atten- tion. All attention to ideas, images, thoughts, etc., is idea- tional attention. The first type of activity involves both sense organ and brain, whereas the second type involves irmne- diately only the brain. A. In Sensory Attention.— In normal sensory attention muscular movements seem always to be concerned. These movements are accommodatory, and are calculated to put the sense organs in the best attitude to receive distinct im- pressions from the objects stimulating them. In vision, for lOO PSYCHOLOGY example, if we see to best advantage, the eyes in;ust converge upon the objects at which we are looking, the lenses must be accommodated to the distance of the object, and oftentimes the head must be turned, in order to permit the most effective visual operation. In hearing, we similarly tend to turn the head toward the source of the sound, or at all events, to turn in that direction the more sensitive of our ears. In taste, we press against the substance in the mouth with the tongue in order to detect most fully its flavour. In smelling, we inhale in order to bring the odorous particles against the olfactory membrane at the upper part of the nasal cavity. In touch, we explore the object with the hand, if we desire ac- curate information of its tactual characteristics. We find a similar state of things true, as regards all our sensations, when we make them the object of direct attention. Each of these cases illustrates the function of the sensory- motor circuit. The light rays falling upon the retina set up currents in sensory nerves, which are transmitted to cells in control of the muscles of the eyes; and these cells in turn send out impulses, which result in convergence and accommo- dation. In some cases the sensory impulse may originate in a cortical centre, or in a sense-organ other than that which experiences the modifications of the accommodatory move- ment. Thus, the hand may be moved in response to an idea, or in response to a stimulus from the eye, arid not from the skin of the hand itself. B. In Ideational Attention. — Psychologists have observed a similar kind of muscular accommodation when our atten- tion is directed to intellectual processes. Thus, if we close our eyes and attempt to get a visual mental picture of some particular place, it will generally be found that the eyes tend to turn in the supposed direction of the imagined local- ity. In attempting to recall an odour we almost inevitably make slight movements of inhalation. In calling up images of taste the tongue moves and salivation is stimulated. ATTENTION lot Furthermore;, the effort to fix our attention firmly upon any train of thought is generally accompanied by a strong ten- dency to assume some specific bodily attitude, in which we somewhat unconsciously seek to prevent the distraction of our attention by outside disturbances. In this effort the brows are often wrinkled, the breathing impeded, the body bent over and held rigid, the hands clenched, the head tilted in this way or that. The attitudes which we thus assume evidently share with the sense-organ accommodations already mentioned, the function of putting the organism in the most advantageous position for meeting the special demand mo- mentarily laid upon it. Indeed, many of these attitudes are characteristic of all attentive process whether sensory or ideational. The psychophysical effort at concentration over- flows in movements calculated to assist in reaching the desired end. The actual value of these movements probably varies greatly, and depends (1) upon their success in eliminating, or neutralising, the effect of the disturbing stimuli from without; and (2) in their contribution, through their corti- cal effects, toward the continuation of the ongoing activity. Thus, if more nervous energy is being liberated than can be properly disposed of by the pathways of discharge involved in the special matter in hand, these overflow motor pathways may be called in to take care of the excess of neural activity, and so indirectly further the ongoing occupation. C. Involuntary Muscular Processes and Attention. — Experiments show that the involuntary muscular processes, such as those of respiration and circulation, also reflect the changes in attention. T\Tien attention is much perturbed, they display rapid and relatively violent oscillations. When, on the other hand, attention moves along smoothly, these motor reactions are also stable. Extensive investigations have also been made to establish the correlation of certain fixed forms of circulatory and respiratory activities with voluntary and involuntary attention respectively. The results are too 102 PSYCHOLOGY complex and too imperfectly confirmed to justify description here. Sensory Indices of Motor Attitudes in Attention. — The motor activities which accompany processes of attention necessarily, at least in the case of the voluntary muscles, send back toward the cortex sensory impulses, which may then enter into the general field of consciousness to modify its com- plexion and tone. These are sometimes spoken of as the "strain sensations" of attention. It seems probable that there is a small group which characterises in some measure all attention, and that the use of any special sense, or any special form of ideational process, involves another specific and relatively constant group. The intensity of these sensa- tions necessarily varies widely from time to time, and is com- monly greatest in cases of intense voluntary attention. The muscles most regularly and most obviously affected are those of the face, throat, and chest, although the hand and other parts of the body may be involved. The breathing move- ments are almost sure to be involved in cases of vigorous attention. Dr. Gordon has suggested another interesting explanation of the function of these strain sensations. It is possible that in attempting, for example, to force our attention along some mentally difficult path, we primarily crave more ner- vous excitement and stimulation, more push a tergo; and these muscular activities setting up definite sensory im- pulses, which return to the cortex, may possibly furnish this needed help. It may well be that all these accounts of the motor aspects of attention are correct. After what has been said it is, perhaps, unnecessary to insist that motor processes are bound up in an inextricable way with the movements of attention, both as leading up to its effective activity and as secondary consequences of its operation. The idea of the sensory-motor circuit proves to be radically implicated, there- fore, in every form of conscious action. ATTENTION 1 03 Genetic Features of Attention. — All the evidence which we can command, coming in part from the examination of our own mental operations as adults, and in part from ob- serving how children deal with the objects about them, points to the notion that the active portion of the field of con- sciousness is from the very first given over to the double process of pulling apart and putting together the various ele- ments of experience. These two processes are commonly known as dissociation and association. It seems to be fairly certain that at the outset of life consciousness is extremely vague and crude in its organisation. To begin with, there is, perhaps, no definite distinction felt between the various kinds of sensations, visual, auditory, tactual, etc. Certainly the process of distinguishing the various kinds of sensory qualities within the range of any given sense series — like the spectral colours in the field of vision — is quite slow in developing. The various colours are undoubtedly distinguished from one another very imperfectly even up to a late period in childhood. The discrimination of differences in form definitely antedates this ability to recognise colour distinc- tions and in cases of arrested development the latter may never be acquired satisfactorily even though the former is relatively normal. ISTevertheless, after the first moment of consciousness the mind is constantly at work, splitting up experiences which previously were felt as simple, and bring- ing about an increasingly definite awareness of the several distinguishable qualities within them. The analytical activ- ity disclosed in attention is what we called above dissociation, or discrimination. Although we shall have a great deal to say about it under other titles further on in the book, we must glance at some of its more conspicuous features here. II— DISCEIMINATION AND ASSOCIATION Analytic Aspect of Attention: Discrimination. — When I04 PSYCHOLOGY the different distinguishable elements of any state of con- sciousness blend with one another, so that they lose their in- dividuality, we speak of the resulting condition as a case of fusion. Thus, the partial tones in a piano note are generally lost to us as separate sounds, and we seem to hear only a single musical tone. Similarly, when we grasp a book we seldom distinguish the sensations of pressure from those of temperature and tendinous strain. These sensations fuse. Again, the sensations which we get when eating onions, or when drinking coffee, we commonly speak of as being tastes. In point of fact, they largely depend for their characteristic quality upon smell sensations, which fuse with the tastes and in consequence are entirely overlooked by us. This can readily be proved by stopping the nostrils when the substances are taken into the mouth. The effect of a severe cold in the head in depriving us of our sense of taste is really largely attributable to its influence on the membranes of the nose. Now, it seems probable that the original tendencies of all sensory stimuli, which impinge upon our sense organs simul- taneously, is to fuse in just this same fashion; so that were it not for this discriminative activity which we are describing, we might remain oblivious to much of the complexity of the objective world. Undoubtedly the compelling motive to such discrimination is in the first instance the necessity for practical control over objects. If we could deal with objects successfully while disregarding differences of colour and form and size, dis- crimination would fail to develop. But this of course is not the case. The situation is similar to that noticed in the last chapter where we found gross general movements splitting up into finer and more precise ones. Meantime, it must not be overlooked that once we have succeeded in analysing some of these originally fusing qualities, we may find their distinct- ness and separateness enhanced by being experienced simul- taneously. Colours, like black and white, red and green, may ATTENTION loj gain in definiteness and individuality by the contrast effects of juxtaposition. Primary Conditions of Discrimination. — However it may be in later life, there can be no question that during the first year or two the great agent in furthering discrimi- nation is the change in the objective stimuli, which affect the sense organs from moment to moment. Thus, sounds sometimes occur simultaneously with stimulations of colour, and sometimes they do not. Stimulations of red sometimes occur together with stimulations of blue, and sometimes with white. These changes in the mode of sensory stimu- lation necessarily produce different forms of cortical re- ., , . , „ 0) ( ST ) =1 Q action; and, as con- sciousness is condi- tioned by these cortical activities, we have thus a ( tk ) =2Q==i+x O (2) ::=z = 2 Q basis for different ^ ^ =t+s.+j<=»3Q states of conscious- / ^ ness. That we are able to recognize the fact that one = 2(2=S+X Fig. 35. state of consciousness differs from a second, and is like a third, is an ultimate fact which we cannot further explain. All psychologists agree that this is a fundamental attribute of consciousness, and, so far as concerns the conditions under which we actually come in the first instance to attain this awareness of differences, the description we have just given seems to represent the undoubted facts. We can put the matter diagrammatically, as in figure 35. So long as a certain taste sensation T, and a certain smell sensation S, are always given us together, we fail to note the complexity of the sensation, and we experience (1) a fusion possessing lo6 PSYCHOLOGY a single quality, 1 Q. When, however, (2) the sensation T, or the sensation >S'^ is given alone, or (3) in combination with some oilier quality, we may, when the complex TB is again experienced, discern the two qualities — ^Q, i. e., T and 8. In experiencing either TX or SX we shall also be in a posi- tion to discriminate X. In each case we have, by varying the concomitants, produced a new psychophysical condition, in part different from and in part like its predecessors, and in this way we have provided the prerequisites for the analysis of compounds. Evidently, if these are the preconditions of our original capacity for the dissociating process, any device which facili- tates the arousal of different nervous conditions will assist us in making our discriminations. Submitting objects to successive, instead of simultaneous, inspection produces a maximum of nervous difference; and we find accordingly that if we wish, for example, to detect the heavier of two objects of nearly equal weight, we judge most accurately when we lift them immediately in succession. If we wish to tell whether or no two colours match, we let the eye pass rapidly from one to the other, etc. Of course, when the objects stimulate different sense organs there is already considerable difference in the nervous processes resulting, and to dis- criminate among them it is only necessary to let either sense be stimulated independently. The use of words has been shown experimentally to assist in discrimination in cases in- volving memory, e. g., when we attempt to remember and identify colours, if we can assign them definite names, our task is much facilitated. The kind of discrimination, or comparison, which occurs among ideas in the higher pro- cesses of reflection, reasoning, etc., we shall consider at a later point. The form of dissociation which we have de- scribed clearly underlies the higher form, because it is con- cerned with our primary analysis into its rudimentary features of the world as we first know it- ATTENTION I07 Synthetic Features of Attention: Simultaneous Associa- tion. — Hand in hand with these dissociative, analyticaJ, activities is to be found a synthetic process, "which serves to unite the various dissevered elements, and to which the name association is commonly given. In a logical sense, one phase of this associative process really precedes and underlies the dissociative activity; for it is evident that if we are to dif- ferentiate the two qualities A and B from one another, they must already be associated in some kind of fusion such as we have just been describing. Thus, to distinguish the colour white from the colovir black upon this printed page involves not only that the black and the white objects shall be side by side in the space before me, but also that they shall in a way be together in my mind. It is clear that every act of attention must involve in some degree both discrimination and this form of "simul- taneous association.'^ We may, for example, remark that the colours upon a postage stamp are red and white. Such an act is evidently one of discrimination. But it is also quite as truly one of association, for the qualities must be experienced together, must be mentally synthesised, that this special kind of discrimination may occur at all. It has already been stated that when sensations are expe- rienced in forms where they blend in such a way as to lose something of their individuality, e. g., the partial tones of a violin note, psychologists sometimes speak of the simultaneous association involved as a fusion. When the conscious complex emphasises the individuality of its components or leaves this unimpaired, as often occurs in the perception of colours, it is by certain authors called a colligation.'^ Mental images and ideas show the same sort of differentiation in this particular as do sensations. *Tlie term complication is sometimes applied to combinations involving elements from different senses. We shall mention these cases in our study of perception. io8 PSYCHOLOGY Successive Association. — There is another form of associa- tioiij known i\s successive association, a term which is com- monly restricted to the sequence of our ideas as they pass through the mind. We shall discuss it in connection with imagery and the higher cognitive functions. Even this kind of association of ideas, however, evidently involves discrimi- nation; for the ideas must be noticed as different, in order that they may be separate ideas at all. And conversely, so far as we remark differences in successive moments of con- sciousness, we must admit the presence of associative factors of some kind or other, uniting the several temporally distinct contents of consciousness with one another. Generalising, then, we may say that attention involves both a synthetic and an analytic activity. Sometimes our primary purpose and interest in attending is to analyse and discrim- inate, but we cannot accomplish this without simultaneously employing association. And similarly, although we may be ostensibly engaged in connecting, or associating, the various items of our experience with one another, the execution of our task inevitably involves us in discrimination. CHAPTER V SENSATION Elementary Sensory Processes. — The first step in the activity of the sensory-motor circuit, which represents, as we have seen, the unit of action in the nervous system, is the sensory stimulation. This stimulation is reported in con- sciousness as a sensation, at which point we shall accordingly begin our detailed study of the various portions of our psycho- logical processes.* Our task as psychologists requires that we study each of the great groups of sensation in order to detect its intrinsic psychical peculiarities. This will bring to our notice, begin- ning with the more rudimentary senses, cutaneous, organic, kinaesthetic, gustatory, olfactory, auditory and visual sen- sations. We must analyse these as far as we can into their elementary qualities and attempt to discover the relations of these qualities to one another. We shall notice in each case the more important of the known physical and physiological facts upon which the sensations depend. Toward the end of the chapter we shall describe the function of sensation and consider a distinction which psychologists make between sensation and perception, both of which are sensory pro- cesses. Our undertaking will necessarily involve our examining *Some psychologists regard the feelings of pleasure and pain a3 even more primordial than sensation in this primitive sensory-motor activity of the organism. Be this as it may, we shall find it practically more convenient to examine the cognitive functions of the organism first; that is to say, those which inform us most definitely of objects, including our own bodies. no PSYCHOLOGY various aspects of consciousness one at a time, and we must unavoidably turn our backs temporarily on most of the proc- esses, apart from the special one we are for the moment engaged in studying. We must bear contantly in mind, there- fore, this partial and tentative mode of procedure, remember- ing that the mind, which we thus analyse piecemeal, is in point of fact a real unit. It will assist us to gain a proper appreciation of the sig- nificance of sensation to remark at the outset certain facts about the evolution of sense organs. The Evolution of Sense Organs. — That it may be put into the most delicate and complete accord with the world in which it is placed, the organism must be capable of responding to the various objects found therein. To this end we find the sense organs so devised that they may give information about the most widely differing kinds of physical existence. Each form of sensation which we possess is apparently connected with the activity of a specially constituted receiving ap- paratus. In some cases this apparatus Is extremely complex^ as in the eye for example ; in other instances it is very simple, as in the ease of the so-called pain nerves of which we shall speak in a moment. These end-organs are connected with special parts of the cerebral cortex which they incite to activity. These cortical connections we examined in Chap- ter II. There seems to be no doubt that even very simple forms of organism are sensitive in a rude way to most, if not all, of the types of sensory stimuli to which human beings respond, e. g., light, sound, mechanical impact, etc. This is simply another way of saying that protoplasm itself is sensitive to these modes of stimulation. But so far as concerns the develop- ment of definitely differentiated sense organs, specially de- vised to receive particular modes of sensory stimuli, the facts seem to indicate great irregularity and wide variation among different organic forms. The kinds of sensitivity which are SENSATION III most certainly and regularly present in the lower orders cor- respond most nearly to the human cutaneous sensations of touch, pain, and temperature. But beyond such a statement as this, we are hardly in a position to offer any definite out- line of sensory development. Not a few animal forms well up in the scale of organisms seem to possess sense organs unknown to man, the nature of whose functions we can, therefore, only speculate about. Moreover, when we come to animals on the level of the birds and quadrupeds, we come upon astonishing anomalies. For example, it seems possible that some birds are essentially destitute of the sense of smell. At all events they make little or no use of it. This is said to be true of vultures. On the other hand, certain dogs seem to live in a world in which smell probably plays a predominant part. Speaking generally, advance to any high level of intelligence is accompanied by an increasing prom- inence of vision and hearing, and a decreasing prominence for the rest of the sensations. This fact seems to be largely due to the superior richness and flexibility of the material supplied by these two senses for elaboration into ideational processes. Moreover, these senses are the ones which afford most detailed and accurate information of objects at a dis- tance — an important consideration in developing organisms. Smell is their only rival in this particular, and for purposes of general orientation, as regards prey, or dangerous animal foes, is made large use of by many wild creatures. We are now ready to pass to a detailed consideration of the several sensations. Analysis of Cutaneous Sensations. — From the skin we obtain as the rudimentary qualities of sensation, cold, warmth, pain, and pressure. Certain psychologists maintain that heat — commonly thought of as merely intense warmth — is quali- tatively distinct from warmth and depends upon the simul- taneous stimulation of both warmth and cold. It is from this viewpoint in reality a fusion, whether it be so sensed or not. 112 PSYCHOLOGY The evidence for our statement, as to the elementary quali- ties of the cutaneous sensations, consists in the careful ex- amination of every kind of psychical experience which we can obtain from the stimulation of the skin. These stimu- lations can be produced by mechanical impact — either push- ing or pulling — by certain chemicals, such as the acids, by electricity, and by temperatures distinctly above or below that of the skin itself. At first, it may seem that we have many other elementary qualities peculiar to cutaneous reactions. Thus, it is com- mon in the older text-books to see such asserted sensations as hardness, softness, wetness, dryness, active and passive touch, sharpness, smoothness, roughness, etc., referred to the skin. It is true, of course, that these several impressions originate in the skin. But they are quite certainly either compounds of pressure with some of the other sensations already mentioned, or else mere modifications of pressure it- self. Thus, if one heat a drop of water to the exact tempera- ture of the sldn, and then place it on the hand, it will prove very difficult to imagine any sensation caused by it other than pressure. Similarly, if a hard and a soft object be made thermally indifferent, and both be laid very gently against the skin, pressure will be the only sensation confidently felt. As the intensity of the pressure increases, the difference will be remarked. But hardness simply means more intense pressure, plus, on most occasions, certain sensations of effort, resistance, or strain, which come from muscles, or tendons, and not from the skin. And so with the other experiences suggested above. When carefully examined, they will all be found capable . of resolution itto pressure, or pressure and some other sensation, like that of temperature, or ten- dinous strain. ^ Itching, tickling, and creepy sensations of the skin prob- ably originate at times from the effects of circulatory changes upon the dermal end-organs. Occasionally, however, they SENSATION 113 are due to very light pressure stimulations. The creepy feel- ing is often a complex of the prickly pain sensations with cold sensations. There seems no reason to postulate any new elementary forms of sense experience because of these reactions. If one takes a cool blunt-pointed object, like a knitting needle, and explores gently some portion of the skin, such as the back of the hand, it will be found that at certain points there flashes out a distinct sensation of cold. At other spots nothing but pressure will be felt and if the impact be very gentle, not a few places will be found from which no sensation at all is gotten. If the point be slightly warmed, a similar series of occasional warmth sensations will be elicited. If a fine broom straw or horse hair be substituted for the knitting needle and the explorations be continued with a gentle pressure, many spots will yield a distinct cut- ting pain sensation. From other spots a somewhat dull sen- sation of pressure will be noted and from still others, the so- called 'pressure spots,' will issue a sensation described by many persons as feeling like a grain of sand caught beneath the skin. This sensation is reported by certain observers to be less simple in composition than the others. It is some- what like a combination of mild pain with pressure. The dull sensations are held to be simply dim, faint sensations from neighbouring 'pressure spots.' Under moderate stimu- lation, then, the skin appears as a delicate mosaic of sensitive and insensitive points. The temperature sensations can be produced by electrical stimulation, and by tapping upon the skin with an object which is thermally indifferent. Moreover, sensations of cold are sometimes gotten from stimulation with objects slightly warm. These are the 'paradox' sensations of von Frey. Such facts would evidently seem to indicate the existence of some special organs for these particular sensations. These organs when stimulated would always respond with a specific sensa- tion, regardless of the nature of the stimulus. The funda- 114 PSYCHOLOGY mental peculiarity of the temperature sense is its ability to effect accommodations to changes in the objective tem- perature. The air feels cold when we first go out-doors on a winter day, but presently we cease to notice it. We accommodate to it. No wholly satisfactory explanation o f this capacity of the tempera- ture nerves has been found. Fig. 36. C, cold spots; H, hot ^. ^n -, -i spots. (McKendrick and Figure 36 shows a rude map Snodgrass after Gold- of the temperature spots, which scheider.) , n ,^ are less numerous than the pressure spots and much less numerous than those respond- ing with pain. Naturally, it often happens that the various sorts of sensi- tive spots (pain, pressure and thermal) are very close to- gether, so that it is frequently possible to secure several kinds of sensations from what is apparently one and the same spot. Furthermore, it is broadly speaking true that if the stimu- lus be made very intense, any portion of the cutaneous sur- face will respond with the appropriate sensation. But the widest variations of sensitivity are encountered. Upon the cornea even the gentlest contact is likely to be painful; whereas there is an area upon the inner surface of the cheek which is said to be quite insensitive to the prick of a needle. Neural Basis of the CTitaneous Sensations. — The facts about the cutaneous end-organs have been strangely difficult to determine and the statements made in this section are in large part frankly conjectural. They represent, however, the best opinion at this time. It may be that the structures pictured as receptive organs are in reality merely protective or something of that kind. They are found in the skin and mucous membranes. (See figure 37.) The sensations of touch or contact probably come from the SENSATION 115 stimulation of minute structures in the dermis — the true skin — (tigure 37C, E), and from nerves ending about the HJ^ Fig. 37. A, a diagrammatic cross section of the skin showing E. L., the horny layer of the epidermis, C. L., the clear layer, G. L., the granular layer, M. L., the mucous layer, P. L., the papillary layer, forming the outer border of the dermis ; N. E., nerve endings, and N. T., the trunks of the nerves. B, diagrammatic cross section of the skin showing a hair and the nerve winding about its base; H., the hair; E. L., horny layer of the epi- dermis; 2V., nerve trunk with terminals, T., about the base of the hair. G, a tactile corpuscle of Meissner. AX., the axonic processes wrapping about the tissue of the corpuscle. A. C, naked axis cylinders. D, end-bulb of Krause. AX., axones entering the bulb; N. F., naked axone fibres; T. C, so-called touch cells; C. T., connective tissue of the skin. E, Pacinian corpuscle; AX., axone entering the corpuscle with axis cylinder terminations at A. C; G. T., connective tissue. F, Ruffini's nerve endings; AX., axones; T. 0., terminal organs; G. T., con- nective tissue. O, termination of sensory nerve in tendon; AX., axone; T., tendon; T. 0., terminal organs. (Modified from Cunningham, Retzius, Morris and Toldt.) roots of the hair (figure 37B). Sensations of cold prob- ably originate from organs in the skin, such as are shown in Il6 PSYCHOLOGY figure 37D, It is possible that sensations of warmth come from the stimulation of special structures, such as are shown in figure 37F; and in the epidermis (the tough outer layer of the skin), as well as elsewhere, are found the so-called free nerve endings, i. e., nerve fibres which become much attenuated and terminate without contact with any special end-organ (figure 15A). The stimulation of these fibres in the epi- dermis is believed to produce the cutting, smarting, burning sensations of physical pain, which must not be confused with the experience of mere disagreeableness.* It is not necessary to repeat in detail what was said in chapter II about the central conduction pathways for these forms of sensory excitation, nor to describe again their cortical centres in the region posterior to Eolando. Genetic Features of Cutaneous Sensations. — The touch, pain, and temperature apparatus in the nervous system is fairly complete at birth. The dependence — at least partial — of the delicacy of the action of the cutaneous senses upon the richness of the supply of nerve endings is suggested by the fact that children have a finer and more accurate sense of touch than adults. In the child there are practically as many * Drs. Head, Rivers and Sherren of London have recently published the results of some interesting experiments on the manner in which sensitivity is restored to the skin and underlying regions, after sec- tion of the sensory nerves. Their results do not bring evidence of any new sense qualities, but may well necessitate a revision of our ideas about the psychological and anatomical relations represented in the cutaneous senses. They find that the afferent fibres may be divided into three groups. ( 1 ) Those which "subserve deep sensi- bility and conduct the impulse by pressure." The fibres of this sys- tem run chiefly in conjunction with motor fibres and are not affeeted by section of the sensory nerves to the skin. They enable accurate localization of vigorour pressure stimuli. (2) A system of fibres ("protopathic") which respond to painful cutaneous stimuli and to extremes of temperature. They may be stimulated also by moving the hairs. They recover their functions relatively rapidly after sec- tion of the sensory nerves. (3) A system of fibres ("epicritic") which respond to very light touch stimuli and convey the power to discriminate stimuli accurately with reference to their size, shape, intensity, etc., as the other fibre systems do not, These fibres re- generate slowly after section. SENSATION 117 nerve endings for any given area of the skin as in the adult. But in the adult these nerves have to supply a much larger area, owing to the spreading of the skin through growth. The difference is most marked on surfaces not regularly used for touching, e. g., the back of the arm. Kinaesthetic Sensation Qualities. — Closely connected with the skin sensations are the kinaesthetic sensations, some- times classified as organic sensations. When one lifts a heavy weight there is quickly noticeable, over and above the pressure sensation in the hand, a feeling of strain in the arm. When the hand is firmly clasped, this strain is also detectable. This sensation without doubt is largely referable to the tendons. There is also undoubtedly a muscle sensa- tion. But without experimental appliances it is hardly pos- sible introspectively to isolate the sensation from the cutaneous and tendinous sensations which accompany it, except in the case of moderate muscular fatigue. The sensa- tion which arises under such conditions of fatigue is the specific sensation concerned. The joints, too, are contributors to this group of sensations, if not directly on their own ac- count, then indirectly through their effect upon the tendons. Certainly we are extremely sensitive to their movements. But there is some difference of expert opinion as to the anatomical and physiological facts involved. The sensation which is experienced when v/e attempt to isolate the joint activity is strikingly like ordinary pressure. This isolation can be accomplished with sufficient accuracy by attaching a heavy weight to a cord, and then, while holding the cord, allowing the weight to sink rapidly to the ground. At the moment when it strikes, one feels a sort of "snap-back" sen- sation in the joints. Movement of particular parts of the body obviously constitutes the normal stimulus to these sen- sations. We notice them almost as distinctly when the parts are moved for us, as when we move them ourselves. Neural Basis of the Kinaesthetic Senses. — It is known Il8 PSYCKOLOGY that sensory nerves are connected with muscle tissues and with the tendons. They are very numerous about the joints. The methods of termination are sufficiently similar to those already described in connection with the skin to render a detailed description superfluous. See figure 37G for sketch of a nerve ending in a tendon. The cortical centres which receive impulses from these nerves are no doubt chiefly in the Eolandic region, presumably posterior to the fissure. Organic Sensations. — The respiratory and circulatory pro- cesses produce certain sensory experiences closely akin to the cutaneous ones, e, g., the sensation of "closeness" in the air, perhaps, comes from a genuine intra-thoracic sensation. The sexual organs have a specific sensory quality, and the alimen- tary tract gives rise to the experiences of nausea, thirst, and hunger. It may, perhaps, be questioned whether these last experiences are not resolvable into other simpler constituent sensation qualities, in which pressure and pain, for example, possibly play a part, and with which the affective factors of pleasantness and unpleasantness are markedly connected. But the disposition among psychologists seems on the whole to be in favour of regarding them as real sensations, with probably some specific end-organ, although the case is far from clear. Pain itself is often ranked as an organic sensation. The pains from the viscera and other deep lying organs must cer- tainly be recognised in addition to the cutaneous pains already mentioned, however they be classified. The massive agony of certain of these pains contrasts strikingly with the ordinary experiences of dermal pain. Moreover, we occasion- ally experience pressure and temperature sensations from the internal surfaces of the body and such sensations should then be designated organic. Properly speaking, the term 'organic sensation' applies to such sensations as report changes in bodily organs by which changes they are caused. The kinsesthetic sensations should strictly be grouped here. But they have functions so im- SENSATION 119 portant for general conscious process as to render it judicious to mention them separately. We have used the term 'organic sensation^ to designate those sensations which indicate most distinctly the progress of the vital internal affairs of the organism. We shall notice one group of sensations which forms a transition from the kinsesthetic to the organic class, i. e., the static sensations. When the whole body is moved, as occurs in a train or an elevator, we receive a distinct group of sensations which, quite apart from vision, report the fact of translation. If the body is whirled, we obtain the sensations of dizziness and dis- turbed equilibrium. Dizziness may of course be produced in many other ways, e. g., by being on high places, by seeing objects in very rapid movement about us, 'and so on. Neural Factors in Organic Sensation. — Our present knowledge of the end-organ arrangements of the sensations from the vital organs is rather too fragmentary and the sub- ject as a whole rather too complex to warrant discussion and detailed exposition here. Speaking broadly, impulses from the sensory nerves of this group probably reach the cerebral cortex in the region immediately posterior to the fissure of Eolando. The static sensations have been referred to the semicircular canals of the internal ear, which it will be more convenient to study in connection with sensations of hearing. It is questioned by competent authority whether they con- tribute to our sense of translocation of the body, except when the movement is of a whirling character. It is at least cer- tain that many other organs contribute to these sensations, notably the eyes and the viscera. We do not naturally refer the sensations to the semicircular canals. We simply find our equilibrium disturbed without localising the organ re- sponsible for the sensation. Undoubtedly the cerebellum par- ticipates in the control of equilibratory movements and consequently in their misbehaviour. The dualities of Taste Sensations. — There are, without ISO PSYCHOLOGY much question, four and only four elementary qualities of taste sensation, i. e., sour, salt, sweet, and bitter. What we commonly call tastes are generally compounds, or fusions, of taste with temperature, pressure, and smell. Thus, as we have remarked at an earlier point, the characteristic taste of onions will be found astonishingly altered, if one close the nostrils firmly before taking the onion into the mouth. Some au- thorities incline to add two other elementary tastes to the list of gustatory qualities, i. e., alkaline and metallic. But on the whole, it seems probable that these are compounds of the others already mentioned. Certainly it is remarkable to see how completely these four suffice to de- scribe the true taste sensations, when we are given a large number of sub- stances to test by taste alone, without knowing in advance what they are to be. To make this experiment satisfactorily, one must see to it that smell is absolutely ruled out, that the temperature of the substances is that of the mouth itself; and one must be careful not to confuse the cutaneous pricking, puckering effects of certain substances, which are not taste sensations at all, with the true taste quality. Furthermore, one must employ solutions to make the test, for many food substances produce characteristic contact sensations which we instantly recognise. Other facts will be mentioned in the next paragraph confirmatory of the view that these four qualities of taste are exhaustive of the elementary forms. Neural and Physiological Basis of Taste. — The cells in the taste buds, found as a rule only in trough-lik« Fig. 38. Taste bud seen in the papilla foliata of a rabbit y 560 d. g, taste bud, showing outer supporting cells; s, fine ends of taste cells ; p, taste pore. ( Mc Kendrick and Snodgrass aftef Stohr.) SENSATION 121 depressions about certain papillae of the tongue (though occasionally elsewhere in the mouth), furnish us with our taste sensations. (Figure 38.) In order to get at these deep-lying cells the stimulus for taste has to be in fluid form. The end-organ cells are not true nerve cells, but are receptive and probably selective cells whose counterparts we shall find in the eye and ear. It seems probable that there is still further differentiation of the forms of this end-organ than is suggested by the mere existence of an end-organ cell; for certain regions, like the base of the tongue, are often espe- cially sensitive to some one taste, in this case bitter. The sides of the tongue are particularly responsive to sour, the tip to sweet and to salt. The centre of the tongue is generally altogether insensitive to taste. The leaves of the plant called gymnema sylvestre will, if they be chewed, paralyse the sen- sitivity for bitter and sweet without affecting the other tastes. Cocaine, if applied to the tongue, causes first a loss of the ability to distinguish bitter, then sweet, and finally salt and sour. Furthermore, some substances, e. g., saccharine, pro- duce one taste in one part of the mouth, and another taste in another part of the mouth. Saccharine is sweet to the tip, and bitter to the base, of the tongue. All these facts are easy to explain, provided there are taste cells, which always respond, however they are stimulated, with some one taste quality. But the facts are not as yet definitely deter- mined, and we must consequently eschew dogmatic statements. The cortical centre for taste is not conclusively estab- lished. It is supposedly near that for smell. It may be added that the sense of taste is well developed at birth, a fact which has, perhaps, a certain evolutionary significance. The sense is often defective in the feeble minded, a condition which suggests the readiness of ani- mals to eat foods whose taste revolts the normal human being. Olfactory Qualities.— It is impossible at the present time to say anything definite about the elementary sense qualities 122 PSYCHOLOGY of smell. The evidence at present available would make it seem probable that the number is large. We seldom make any attempt at classifying odours by their sense qualities, probably because practical exigencies do not require it. Our only common classification is based upon the affective con- sequences of the odour stimuli, which we divide into the two great classes, agreeable and disagreeable. We designate odours by the objects from which they come, e. g., violet, orange, leather, etc., adding occasionally to these terms metaphors borrowed from taste, e. g., sour, sweet, terms which are not always applied unambiguously to the mere sense quality, but often involve reference to affective processes, and to other concomitant activities, both muscular and sensory. For example, a sour smell is often one which stirs up unpleasant gustatory sensations, with choking contractions of the throat. The classification most used in a practical way at the present time is Zwaardemaker's modification of Linngeus' table: 1 — Ethereal smells, including fruit odours. 2 — Aromatic smells, e. g., camphor, spice. 3 — Fragrant smells, e. g., many flowers, violets, sweet peas, etc. 4 — Ambrosiac smells, e. g., musk. 5 — Alliaceous smells, e. g., garlic, chlorine. 6 — Empyreumatic smells, e. g., burning tobacco, buml toast, coffee. 7 — Hircine smells, e. g., cheese. .8 — Virulent smells, e. g., opium. 9 — Nauseous smells, e. g., decaying animal matter. This classification of the table has a purely practical value, however, and cannot be in any way accepted as representing the irreducible sense qualities. Interesting efforts have been made to determine the rela- tions of smell sensations to one another by the method of fatiguing the nose. For example, one smells of some sub- stance until it ceases to be noticed, a condition which super- SENSATION 123 venes rapidly with many odours. Thereupon if other sub- stances are inhaled, it will be found that some of them are clearly noticeable, whereas others are difficult to detect. It is assumed that those difficult to detect are similar in quality to the fatiguing odour. The results of this method are as yet very incomplete. Physiological and Neural Basis of Smell. — The olfactory nerves terminate about the olfactory cells of the mucous membrane lining the upper portion of the nasal cavity, (Figures 39 and 40.) These ceils are themselves true nerve cells. The cells of which we have spoken as possible receiving cells in the skin and tongue, are not themselves nerve cells. Those which re- ceive the stimuli sent to the eye and ear were probably originally epithe- lial cells which have taken o n neural functions. In this particular the olfactory cells are unique. Whether correctly or not, this fact that they are themselves nerve cells has been connected with the fact of their ready fatigue under stimulation. The cortical neurones which receive stimuli from the olfactory organs are in the hippocampal region, as may be seen by reverting to chapter II, figures 13 and 20. In the human being the olfactory membrane lines the upper portion of the back of the nasal cavity, so that the air currents of our breathing do not normally affect it much. But if we inhale vigorously, the air is drawn higher up in this cavity and we at once obtain distinct odour sensations. The stimulus must be in very fine form, generally gaseous, in order to permit this result. Fig. 39. Isolated cells from the olfactory region of rabbit; st, supporting cells; s, short, stiff cilia, or, according to some authorities, cones of mucus re- sembling cilia; r, r, olfactory cells. The nerve process has been torn off the lower cell marked r. (McKendrick and Snodgrass after Stohr. ) 124 PSYCHOLOGY Genetic Features of Olfactory Sensations.— Smell is sup- posed to have developed later than taste and in air-breathing animals this is doubtless true of the sense in its present form. The most acute perceptions of smell are probably not obtained before seven years of age, because of mechanical difficulties in the form of the nostriL The abundance of mucus in infancy has a similar effect, producing obtuse smell sensitivities. Fig. 40. Diagram to show the location of the olfactory end-organs and the course of the air currents when we breathe. 0, the olfactory membrane into which the olfactory nerve comes down through the bone above. The black line numbered 1 indicates the usual course of the air in natural breathing. The lighter line numbered 2 indicates the course of the air when we inhale strongly. (Modified from Zwaardemaker. ) Analysis of Auditory Sensations: A. Noise and Tone. — — Our auditory sensations fall naturally into two great groups — noises and tones. But each of these can be sub- divided again into a very large number of distinguishable qualities. The normal stimuli for hearing are air waves. The greater the amplitude of these waves, the louder the sound. We get the sensation qualities which we call noise when less than two complete vibrations of a sound wave are allowed to reach the ear; or, what is perhaps, owing to the reflection of the sound, the same thing, when the waves which do reach the ear are irregular and non-periodic in their mode of vibration. These irregularities may evidently be indefinite in number, and so we get such differences in the sounds as distinguish, for example, the noise of a train from the noise of a drum. These last mentioned cases, however, are what are called complex noises, and are conceived as made up of aggregations of the simple noises first mentioned, of which we can detect some 550 or more. The sensation of SENSATION 125 tone comes from bodies which vibrate periodically and regu- larly, like the pendulum. Such bodies are represented best by tuning-forks. We can distinguish some 11,000 simple tonal qualities. The differences among these qualities are primarily what we call differences in pitch. These arise from differences in the vibration rates of the sounds. We can hear tones ranging in vibration rate from 16 to 50,000 per second. The great majority of musical experiences arise from tones whose vibration rates fall between 64 and 5000. In the central region of the musical scale, i. e., with vibra- tions ranging from 500 to 1000, keen observers can detect variations in pitch of only one-fifth of a vibration. The tonal element in noise is easily discernible in the differences in pitch which are often manifest. The roar of a freight train crossing a bridge is much deeper than the rattle of a dray on a street pavement. Practically all the sounds which we hear are combinations of tone and noise. The human voice is an excellent example of this fact. In enun- ciating words the vowel sounds represent the tonal element, the consonants the noises. It must be remembered that the musical tones which we commonly hear are not simple, but complex, being constituted of a number of tones — the fundamental and its overtones. The nature, number, and relative intensity of these partial tones determines the timbre of a sound. The characteristic differences in the tone quality of different instruments have this fact as their basis. In the piano, for instance, there is a rich and well-balanced set of the lower partial tones. In the clarinet the odd overtones are predominant; in the flute these particular overtones are few and weak, etc. The evi- dence for these facts is not easily obtained without the use of apparatus. The fact that we can analyse complex tones so that we become clearly conscious of their partial tones, as well as our capacity to remark the constituent notes in a chord or .26 PSYCHOLOGY other group of tones is one of the remarkable things about audition. We shall connect this fact conjecturally "with the construction of the internal ear when we come to speak about the end-organ. It is evidently possible to connect certain of the more fundamental attributes of sound sensations with their physi- cal antecedents. Arranging them in pairs we have: tone = periodic vibration ; noise = non-periodic vibration ; pitch = vibration rate; intensity = amplitude of vibration; tone quality = vibration composition. B. CombinatiGn Tones. — When two tones occur together under certain conditions several additional tones are heard. These supplementary tones are known as combination tones and are divided into difference tones (of the first, second and higher orders), and summation tones. Difference tones of the first order correspond in vibration rate to the differ- ence between the vibration rates of the generating tones. Those of the second order correspond to tones whose vibra- tion rates are equal to twice the rate of the lower generator minus that of the higher.* The summation tones correspond to tones with vibration rates equal to the sum of the rates of the prime tones. These combination tones are not ordinarily noticed by lay observers, but they are often very powerful and undoubtedly contribute to produce certain important musical effects, e. g., in the minor chords. The theories of their production are too numerous and too unset- tled to warrant discussion. It may be that the tones are ordinarily objective (extra-organic) and physical in origin instead of subjective and physiological (intra-organic), as has generally been supposed : or it may prove that sometimes they are objective, sometimes subjective, and sometimes both. C. Consonance and Dissonance, — The consonance and dissonance of tones has long been a subject of psychological perplexity. Certain tones {e. g., C and G on the piano) * Description of the higher orders is omitted. SENSATION 127 fuse with one another, that is to say they lose their individual distinctness. Other tones (e. g., C and Oil) refuse to fuse and are harsh and discordant in their effects upon us. These tonal complexes are generally marked with strong feeling- tone. They are agreeable or disagreeable. On this account we shall defer further discussion of them until we take up the elementary gesthetic feelings. Genetic Features of Audition. — We have once before called attention to the fact that, owing to the presence of mucus in the middle and external ear, the new-born child is generally insensitive to ordinary sounds. The joosition of FlQ. 41. Diagram of the cochlea seen in transverse section. S. T., the scala tympani; S. V., the scala vestibuli; C C, the canal of the cochlea; A. N., the auditory nerve rimning out through the bone to join the canal of the cochlea; B. M., the basilar membrane; R. M., Reisner's membrane; T. M., tectorial membrane; 7. H. C, inner row of hair cells; 0. H. C, outer roAv of hair cells; S. C, supporting cells; R. C, rods of Corti. (Modified from Stewart.) the drum membrane also contributes to this insensitivity. About four days after birth most children will show response to loud sounds by expressions of fright. The sensitivity to high-pitched sounds seems to develop sooner than that to low sounds. Localisation of sounds seems to begin with many children at about four months of age. Children a year and more of age are often extremely sensitive to very weak sounds which older persons cannot hear at all. Neural and Physiological Facts of Audition. — The auditor}^ nerves terminate about the bases of hair cells in the internal ear, such as appear in figures 41 and 43. These 128 PSYCHOLOGY cells are immersed in liquid contained by the sac-like mem- branes of the inner ear. Figure 43 will make evident the relations to one another of the internal, middle, and external ear. The external ear gathers up the sound waves and focusses them upon the drum membrane of the middle ear. The middle ear contains a chain of small bones stretching between the membrane Just mentioned and another smaller membrane on the side of the inner ear. The Eustachian tube comes up from the throat into this middle ear cavity, and whenever v/e swallow allows air to enter from the throat. • ©' Fig. 42. Cross section of the organ of Corti; p and p^, internal and external rods of Corti ; i and i^, internal hair cells ; e^, exter- nal hair cells; mh, basilar membrane; re, nerve fibres leading from the hair cells inward to the central nervous system. (Barker after Retzius and Rauber.) thus keeping the air pressure in the middle ear like that outside. If the pressure were uneven on the two sides, the membrane would be stiffly bulged out or in and could not operate sensitively to impacts of sound waves. The bones and membranes of the middle ear have been supposed to multiply the x>ower of the vibrations they transmit to the inner ear, thus enabling the relatively feeble sound waves in the air to set up vibrations in the liquids of the inner SENSATION 129 ear. (They form a powerful lever system and the receiving membrane has a much larger surface than the delivering mem- brane.) But the discovery of cases in which the mechan- isms of the middle ear have been destroyed without seriously impairing hearing, renders it possible that their function is more protective and less purely acoustical than has been sup- posed. At all events they do not appear to be indispensable. Fig. 43. Diagram of the ear. A, auditory canal of the external ear; B, tympanic membrane separating the external from the middle ear, G ; D, Eustachian tube leading from the middle ear to the throat; E, one of the semicircular canals of the internal ear, arising out of the utricle upon which, as upon the adjacent saccule, fibres from the vestibular branch of the eighth nerve are shown terminating; F, the spiral of the cochlea, through the central pillar of which the auditory nerve is shown entering to spread out toward the hair cells of the cochlea canal, as indicated in figures 41, 42; G, the main trunk of the eighth nerve. (After Hough and Sedgwick.) There are many thousands of the hair cells of the inner ear, and the precise mode of their stimulation is still prob- lematic, despite the numerous explanatory theories in the field. I30 PSYCHOLOGY The cells are mounted chiefly on the sides of the rods of Corti, which form a triangular tunnel as may be seen in figures 41 and 42, These rods rest on the fibres of the basilar membrane which forms the floor of the tunnel and coils about 3.5 times in the spiral cavity of the cochlea. The membrane is considerably broader at the top than at the bottom, so that it affords a series of stretched strings of different lengths like the strings of a harp. It has been generally supposed, following the authority of Helmholtz, that these fibres, or groups of them, could respond *sym- pathetically' when a tone was sounded corresponding to their own natural rate of vibration.* The movement of the fibre was supposed to stimulate the cells resting upon it, where- upon the cerebral cortex would presently receive an excita- tion peculiar to the given tone and different from every other. The fact that the ear can analyse complex tones was referred to this stimulation of special fibres by each element of such com- plexes. Tone deafness and the exist- ence of Hone islands' suggest the correctness of some such theory as the above. Certain persons cannot distinguish any change in pitch over considerable ranges of the scale. This is easily ex- plicable on the basis of the Helmholtz theory, if certain fibres of the basilar membrane are for any reason inca- pacitated. Of late many difficulties have been encountered which the Fig. 44. Membranous laby- rinth ( diagrammatic ) . c, cochlea; s, saccule united by p, the ductus en- dolymphaticus, with u, the utricle, arising from which are seen the three semicircular canals. ( After McKendrick and Snodgrass. ) * If one press gently down a key on a piano and then sing the tone corresponding to the key, the string belonging to the key will be heard giving out the tone which it has taken up 'sympathetically'. SENSATION 131 theory has hardly met successfully. These are physical, physiological, and psychological. But we cannot go into them. Suffice it to say that the facts at present known render it probable that the analysis of tones, however this be brought about, is performed by the mechanisms of the internal ear rather than by the cortex as has been suggested. The cortical centres for audition have already been suf- ficiently described in chapter II. The semicircular canals of the internal ear (figures 43, 44) also contain sensory fibres, which terminate, like the true auditory fibres, about the bases of hair cells. The fluid in the canals contains little calcareous particles called otoliths. When the body moves in any given direction some of these otoliths are supposed to lag behind, because of their inertia, thus striking the hair cell filaments and setting up a sensory disturbance. As the canals are at right angles to one another, the fluids of some one or two of them would always be most affected by a single movement, and the sensory excitations arising from them might thus be connected either reflexly or by experience with speciflc kinds of movements, e. g., for- ward, backward, upward, etc. Of the cerebral cortical regions possibly involved in the activity of these canals nothing specific is known, beyond whatever is included in the disturbance of other sensory processes like vision, whose representation in the cortex is determined. It is known, however, that the cerebellum is engaged in their operation. Analysis of Visual Sensations. — Like the auditory sensa- tions, our visual sensations fall into two general classes — sensations of brightness and sensations of colour. The bright- ness sensations are caused by the impingement upon the retina of mixed light waves of various lengths; thus, what we call white light is made up of light waves of all lengths. Pure colour sensations are produced by homogeneous light waves, or waves of practically equal length. The more homo- 132 PSYCHOLOGY geneous these waves, the more saturated, the purer, the color. As a matter of fact, we never experience colours without get- ting a measure of brightness sensation also. Although it is convenient to distinguish the two forms of sensation from one another, this concomitance must not be forgotten. Under ordinary conditions the brightest region of the spectrum is in the yellow. If the illumination of the spectrum be suf- ficiently lowered, the region of maximum brightness will be transferred from the yellow to the green; and the red end of the spectrum will become relatively darker in colour-tone while the blue end becomes lighter. This phenomenon -is known after its discoverer as the Purkinje phenomenon. As in the case of sound, the intensity of the sensations par- allels the amplitude of the light wave. If we gradually de- crease the intensity of white light, we pass first through a series of shades, to which we should ordinarily apply the name grey, and come finally to black. Black and white are thus the extremes of the brightness series of sensations, and be- tween them occur the various shades of grey. Black is a relative term applicable to great contrasts with white. The retina is itself always active, so that even in perfect darkness we see floating clouds of dim "^idio-retina? light. We are able to distinguish some 700 different brightness qualities between the deepest black and the most brilliant white. We are in the habit of referring to the spectral colours, or qualities, as being seven in number, i. e., red, orange, yellow, green, blue, indigo-blue, and violet. This is, however, a merely practical and somewhat arbitrary division. These names apply to distinctions in colour tone which we promptly and easily remark when looking at a sunlight spectrum. But in reality the colour between pure green and pure blue is just as truly entitled to a separate name as is orange, a colour which distinctly suggests both red and yellow. Purple, too, which can be formed by mixing red and violet, the colours at the ends of the spectrum, is a perfectly genuine colour quality, SENSATION 133 deserving to rank in this respect with the spectrum colours themselves. When we are given proper experimental condi- tions we find we can distinguish some 150 spectral qualities. This includes the purple. Some 30,000 distinguishable qualities can be produced by combining the several spectral qualities (150) with the bright- ness qualities (700). Thus red, for example, can be mixed with white to produce various tints, which we call pink; or with black to produce various shades, which we designate brown. Figure 45 displays in ^ a general way these relations. Elementary Colour Rela- tions: (1) Mixtures and Complementaries. — If we now apply to vision the mode of analysis we have employed heretofore in the case of other sensations, and attempt to re- duce the visual spectral quali- ties, apart from brightness, to those which seem really ele- mentary, we shall find four such colours remaining, i. e., red, yellow, green, and blue. All the others, when closely in- spected, appear to us to be compounds. Orange, we have already remarked, appears both reddish and yellowish. Violet has traces both of blue and red, and so with all the transitional hues leading from one of these elementary colours to another. Moreover, if we be given these four colours, we can, as we should naturally expect, produce all the other spectral hues by Fig. 45. The colour pyramid. The line WB corresponds to the white-black series of colours; the plane Bl.RYG represents the most satur- ated spectral colours, e. g., blue, red, green. The lines joining W and B with the letters representing the several spectral colours, e. g., Bl. and Q, illustrate the transitional tints and shades. (After Ebbing- haus.) 134 PSYCHOLOGY mixing these elements in proper proportions. Among the mix- tures which we can make in this way are certain very peculiar ones, which result when we take two such colours as yellow and blue, or red and blue-green. • These pairs of colours, when mixed together, give us, instead of a new spectral hue, simply grey. Colours whose mixture results thus in grey are called complementary colours, and every colour has some comple- mentary in the spectral series, except green, whose comple- mentary is purple, a mixture of red and blue. (Figure 46 shows these relations.) (2) After-images. — Our visual sensations are in one par- ticular very remarkable, as compared with our sensations of other kinds. The obvious after-effects of sensory stimulation last longer and are more peculiar than is generally the case elsewhere. Neglecting minor variations, there are two prin- cipal forms of after-images, as they are called, i. e., positive and negative. After-sensations would, perhaps, be the better term for them. If one suddenly looks at a very bright light, and then closes the eyes, the light continues to be seen for some seconds in approximately its proper intensity and hue. This phenomenon is a positive after-image. If one looks for a few seconds fixedly at a bit of blue paper, and then closes the eyes, or turns them upon some neutral grey back-ground, one sees a yellow patch corresponding in shape to the blue stimulus. This is a negative image. Negative images invert the relations of brightness in the stimulus, so that what was white in the object appears black in the after-image, and vice versa. They also convert all spectral colours and their com- pounds into their several complementaries. While all the senses display after-effects similar to the positive visual after- image, none of them has anything precisely comparable with the negative image. (3) Colour Contrast. — The phenomena of contrast also, although characterising in a measure all sense domains, and for that matter all conscious processes, are especially striking SENSATION ^3S in vision. Yellow and blue appear respectively yellower and bluer, when seen side by side, than when seen apart. This seems to be largely because of the fact that the eye moves slightly from one to the other; and the eye fatigued for blue already has a disposition to react with the yellow after- image. If the part of the retina containing this yellow after-image process is then exposed to the real objective yel- low, the power of the stimulus is much enhanced, and we see a deeper, more intense yellow than we otherwise should. This RED" '^^.W33yo-3n-^^ Fig. 46. The colours at opposite ends of any diameter of the circle produce grey, if mixed with one another. Purple, which is the complementary colour to green, is not found in the spectrum, but is produced by a mixture of the end-colours of the spectrum, red and violet. Colours opposite blank seg- ments are psychologically pure and elementary. Colours opposite shaded segments are composite. phenomenon is called successive contrast. Simultaneous con- trast is an even more interesting phenomenon, and may be illustrated by putting a small bit of grey paper upon any coloured field, and then covering the whole with thin white tissue paper. The grey patch will, under such conditions, 136 PSYCHOLOGY always appear as of a colour complementary to that of the field, i. e., it will appear blue when the field is yellow ; yellow, when it is blue; reddish when it is green, etc. The explana- tions offered for this phenomenon would take us too far into physiological psycholog}^, and we must rest content with the general conclusion that our colour sensations are dependent, not only upon the colour of the object immediately fixated, but also upon the colours surrounding it, and upon the im- mediately preceding stimulation. (4) Defects in Colour Vision. — Finally, we may remark, that the peripheral portions of the retina are seriously de- fective in their colour reactions. Accurate colour vision belongs only to the central portion of the retina around the fovea. According to most observers, red and green are only seen accurately for a short distance outside this region. Yel- low and blue are lost next, and in the extreme periphery all colours appear white or grey. This condition suggests the pathological colour-blindness from which many persons suffer even at the fovea. Eecent investigations indicate that pos- sibly all the spectral colours can be seen at the periphery, provided their intensity be sufficient. These observations imply the existence of colour weakness in the marginal re- gions of the retina, rather than true colour-blindness. Pathological Colour Blindness. — Colour-blindness is some- times, but very rarely, total. The patient sees all colours as white, grey, or black. Two types of partial colour-blindness are recognised, the one red-green blindness with two subordi- nate forms, and the other blue-yellow blindness. In red- green blindness the spectrum is seen as half yellow and half blue. The quality of the yellow or blue changes with the region of the spectrum observed. In one type of this form of blindness the greatest brightness of colour is seen in the pure yellow, and the red end of the spectDim is relatively bright. The other type finds the brightest colour in yellow- greeUj, and sees the red end of the spectrum relatively dark. SENSATION 137 In both types a neutral grey band is seen between the blue and the yellow regions of the spectrum. In blue-yellow blindness the violet end of the spectrum is dark and little saturated. Yellow and white are confused. This classifica- tion is Hering's. It should be added that many persons are slightly defective in their colour vision without properly be- longing in the group of the colour blind. Theories of Colour Vision. — Of the many theories of colour vision that of Helmholtz is probably most widely known, although it is quite certainly untenable. It assumes three fundamental colours, red, green, and violet, by com- binations of which all the other colours including white are produced. For example, red and green will produce yel- low; red and violet, purple; and all three elementary colours taken together will produce white. It explains the facts of colour mixture well, but it is unable to account for the psy- chological simplicity of blue and yellow, which do not seem to us compounded of other colours. Orange, for instance, instantly suggests to us the red and yellow of which it is com- posed. The facts of colour-blindness, to mention nothing further, are inexplicable by it. Hering's theory is at present probably most widely held. It assumes three fundamental pairs of colours, white-black, blue-yellow, and green-red. These pairs are in relations of opposition to one another such that if one member of a group be stimulated, the other member must become active before the equilibrium of the retina is restored. The black-white substance is always stimulated by light of every kind and it is evolutionarily the oldest, red-green being the most recently acquired. Mixtures, complementary effects and after-images can all be accoiinted for by the theory. Mixtures are explained as in the Helmholtz theory. The positive after-image results from the continuation of the effect of the stimulus. The negative image arises from the activity of the colour pro- cesses antagonistic to those aroused by the stimulus. Com- 138 PSYCHOLOGY plementary colours simply offset one another and leave the grey of the black- white process. Unfortunately the green which is the complementary of spectral red is not pure green, as it apparently should be, but blue-green and there are some other difficulties too technical to discuss here, which render the theory imperfectly satisfactory. The theory at present apparently most adequate to the various facts is that of Mrs. Ladd-Franklin, although scholars have not generally conceded its truth. Mrs. Franklin assumes that the retina originally responded only to differences in brightness. The outer region of the retina is still in this condition as are probably the retinge of certain of the lower animals. The conscious quality corresponding to this stimulus is grey. In the course of evolution the chemical substance which originally gave rise to sensations of grey only, has been diffentiated so that the various spectral colours produce partial disintegration of it and lead to the sensations which we now see from red to violet. The first differentiation which took place corre- sponded to the colours blue and yellow, and we consequently can see these hues farther out on the retina than red and green, for which sensitivity was later evolved. The yellow process is supposed to differentiate into red and green. The blue has remained relatively unchanged. The grey of com- plementary colours is explained by the entire distintegration of the original visual substance by the summative effects of the partial disintegrations which have been evolved from it. Thus when yellow and blue are mixed, each colour disinte- grates a portion of the original visual substance, and together they effect a complete disintegration of it. The facts of colour mixtures can be explained much as in other theories. Contrast phenomena are due to the progressive break down of the chemical substance assisted in certain cases by the circulation. Although in this account emphasis has been laid upon the SENSATION 139 genetic aspects of the theory, Mrs. Franklin regards these considerations rather as confirmatory of her view than as r * Seler. Fig. 47. Opt., optic nerve; Fov. c, fovea centralis; Scler., sclerotic; Chor., choroid; Ret., retina; Conj., conjimctiva; Pr. cil., ciliary processes by means of which lens is adjusted; Cam. ant., anterior chamber filled with aqueous humour; p, posterior chamber. Just below p the capsule and ligament supporting the lens are shown attached to the ciliary processes. Corpus vitreum, the vitreous humour of the main cavity of the eye-ball. affording it a foundation. She starts from the fundamental and immediate facts of colour vision, such, for example, as I40 PSYCHOLOGY (I the basic differences in quality among the colours red, yellow, green and blue. Physiological and Neural Basis of Vision: A. The Eye- ball. — The essential anatomical facts about the eye are shown in iigures 47 and 48. The eye is a small spherically shaped dark-room, the inner walls of which are covered with the sensitive retinal membrane. Light is admitted to this mem- brane through the aperture in the iris. The light passes first through the transparent spherical cornea where it is refracted (figures 47 and 50) ; then into the anterior chamber filled with a clear fluid known as the "^aqueous humour/ thence through the lens where -S - it is again refracted, so that it may form a per- fect image on the retina, after which it passes through the Vitreous humour,' thus finally reaching the retina where it sets up neural changes that are transmitted to ^ the cerebral cortex. Ch The eye has a tough, S thick outer coat, the scle- Scheme of retinal fibres, rotic, to which are at- after Kuss.) lYop, optic tached the large muscles nerve; S, sclerotic; Ch, cnoroid; B, -, t ■-, ,^ retina; P, papilla (blind spot, that move it. inside the where no retinal structure is gderotic is another mem- ' ' brane, the choroid, which carries blood vessels and is provided with a dense, dark pig- ment that renders the inside of the eye essentially impervious to all light, save that which comes through the opening in the iris. Inside the choroid again is the retina itself, shown in figures 48 and 49. By contracting and expanding, the iris 'P - Ch Fig. 48 (James SENSATION 141 alters the amount of light admitted in such a way as to best serve clear vision. In dim lights it expands to allow entrance to more light, in bright lights it contracts. Fig. 49. Scheme of the structure of the retina. A, layer of rods and cones; a, rods; 6, cones; E, layer of bipolar cells; Q, layer of large ganglion cells; H, layer of nerve fibres; s, centrifugal nerve fibre. (Barker after Ramon y Cajal.) B. Convergence and Accommodation. — By means of six muscles which are attached to the external surfaces of each eye we are enabled to direct them toward any object at which we may wish to look. This process is convergence, or divergence, as the case may be. By means of the lens in each eye, which can be made more or less convex, the rays of light from the object at which we are looking are brought to a focus upon the so-called fovea centralis, the central spot of the retina and the point of clearest vision ; and thus we secure a clear, well-defined image upon each retina. This act is called accommodation. 142 PSYCHOLOGY The cornea also plays an important part in bending the light rays into the proper directions for clear vision and it is to defects in the sphericity of its surfaces that astigmatism is generally due. The rays ■ coming from a perpendicular line, for example, may be bent more sharply than those coming from a horizontal line. In consequence they cannot both be seen clearly at once. If one is properly accom- modated for, the other will have its light rays focussed either in front of, or behind, the retina. Short sightedness and far sightedness are ordinarily due to faulty form of the eye- ball or the lens. Bays of light instead of coming to a focus on the retina, do so in front of, or behind, its surface, so that the images are blurred and indistinct. Lenses or prisms put in front of the cornea are used to offset these accom- modatory defects. (Figure 50.) Sometimes the muscles which move the eye-balls are not well balanced in power and then prisms may be used to lessen the work done by the weak muscles. C. The Retina. — The retina, which differs from all the other sense organs in being in reality a part of the brain removed by growth from its original location, contains a most elaborate series of structures. These are shown in figure 49. The optic nerves enter from the back of each eyeball, and the nerve fibres are then distributed radially all over the spherical surfaces of the eyes, as far forward as the lens. (Figures 47, 48.) The fibres turn backward, away from the centre of the eye, and lose themselves among the basal cells of the retinal structure. The light waves make their way in through the dioptric media of the eye, as already described, and finally, after passing through the transparent optic fibres, come to the retinal end-organs, the rods and cones. (Figures 47 to 49.) At this point the physical ether vibrations which we call light set up physiological changes in the nerve, and the nervous current runs backward along the nerve fibres, and so to the brain. SENSATION 143 At the point where the optic nerve enters the cup of the eye there is no retinal membrane. This is the blind spot. (Figure 48.) It is slightly nasalward from the fovea and its presence can easily be demonstrated by placing two dots three inches apart on a sheet of paper. By closing the left Fig. 50. Diagram show- ing difference between •normal (A), myopic or near-sighted {B) and hypermetropic or far-sighted (C) eyes. In A rays of light from objects at a dis- tance come to a focus precisely upon the retinal surface. In B they come to a focus too soon and are di- verging again when they reach the retina. In C they do not come to a focus until after they have passed be- yond the retina. In B and G the dotted lines represent the course of rays after correction by glasses put in front of the eyes. The diagram may also serve to il- lustrate astigmatism by supposing that the lines in A represent the vertical rays from an object, which in such a case come to a focus properly on the retina, while those in S or C represent the horizontal rays which come to a focus either in front of, or behind the retina. In such an instance it is evident that objects would be seen blurred in all diameters other than those which come to a focus on the retina, as do the vertical ones. (After Howell.) eye and looking at the left-hand dot, while moving the paper to and from the face, a position will be found where the second dot wholly disappears. The retina responds to vibration rates of ether between 144 PSYCHOLOGY 440 trillion and 790 trillion per second. These are the rates of the light waves of the visible spectrum of the sun. The rods and cones are distributed differently over the retinal surface. The cones are in exclusive possession of the foveal depression, the point of clearest vision. They decrease in number and are gradually displaced by the rods as we pass toward the periphery of the retina, until at the extreme forward limits of that membrane the rods alone are found. There is not a little evidence to indicate that the rods mediate only brightness sensations and that their most important fimctions are perhaps connected with vision in dim lights.* Certain it is that we are often able to notice faint lights with the periphery of the eye, where they are numerous, which are not visible at the fovea. This can be demonstrated upon faint stars. It is often noticed at sea where the lights of distant vessels can be thus discerned when invisible to direct vision. The cones are probably then the important organs for colour vision. The cortical centres for vision in the occipital lobes have already been described at some length in chapter II. * The rods contain a substance known as 'visual purple' which bleaches rapidly under the influence of light. It has been suggested that the Purkinje phenomenon, mentioned in an earlier paragraph, may find its explanation in the way in which this visual purple affects the retinal action of coloured light. This substance is bleached most rapidly by green light, a trifle less rapidly by blue light, and least rapidly by red light. The colours at the red end of the spectrum may consequently produce less retinal effect on the visual processes in the rods, than do those at the blue end. On the basis of a theory such as that of Mrs. Ladd-Franklin, this fact should result in decreasing the relative brightness of the red end of the spectrum. According to this theory, sensations of brightness are occasioned by the disintegration of the primitive colour molecule found in the rods. As the green and blue rays Avould operate more effectively on the retina in dim lights than the red rays, they would break down this molecule more rapidly and vigorously, and the resulting brightness sensations would be more intense. Thus the blue end of the spectrum would appear brighter than the red end. The fact that the Purkinje phenomenon is said not to be present in foveal vision, and the further fact that the operation of the visual purple is practically confined to vision in dim lights, would tend to con- firm such an explanation as this. SENSATION 145 Genetic Facts of Vision. — The retina is well developed at birth, and some children apparently have a slight control over the movements of fixation at birth. This is, however, rare, and such control generally does not come until the third week. But there is much variation. Older children surpass adults in their ability to see in a dim light, and to see small objects at a distance. This is probably because the optical media, e. g., the humours of the eye, etc., are with them more transparent. The colour sense is often apparently defective in children. But this probably means simply a lack of experience in distinguishing colours. The brighter colours are generally preferred. Genuine colour blindness is extremely rare among girls, whereas perhaps one in every twenty-five or thirty boys is defective. Summary of Sensation Qualities. — After our analysis of the several types of sensation we may now bring together certain of our results in numerical form. If we consider only the irreducible sense qualities, like redness and sweetness, abstractly considered, and call these the sensation elements, we have probably not more than 20 or 25 when smell and sound are left out of the count. The problem of reduction to simple sense forms is, in the case of these last two groups of sensations, fraught with great difficulty and uncertainty. But if we take into account the actual concrete sensory quali- ties as we find them, e. g., red combined with a given bright- ness, we are supplied with more than 42,000 distinguishable qualities. This latter figure again disregards smell, about which no confident statement can be made. General Characteristic of the Sensation Quality. — The fundamental characteristic common to all the sensations is a certain something which they occasion in us, for which shock is possibly the most appropriate name. This characterises all transition in consciousness, and especially consciousness of immediate sense activities. The Intensity of Sensations. — We have remarked incident- 146 PSYCHOLOGY ally a number of times in this chapter, that our sensations originate from the stimulation of specific sense-organs by some form of motion in the physical world about us, such, for example, as the air waves, the ether waves, the heat waves, etc. But it is not only necessary that these various forms of stimuli should fall upon the sense organs. It is also nec- essary that they should possess sufficient intensity, if we are to become conscious of them. A very faint light, a very faint sound, a very faint odour, may fail altogether to produce a sensation in us. The point at which such a stimulus becomes intense enough to produce a sensation is called the limen, or the threshold. It is also a matter of frequent observatiorv that when sensory stimuli become very intense, the}'' cease to be felt as they were before, and we experience pain instead. A very bright and blinding light may cause acute pain. A loud, shrill sound, extreme heat, and extreme cold are all painful. The point at which the various stimuli are thus felt as painful is known as the upper limit of sensation. Between the limen and the upper limit fall an indefinite number of gradations of sensory intensities. It should be noted in passing, that certain olfactory and gustatory stimuli can hardly be obtained in sufficient intensity to be called painful; and also that many very weak sensations are unpleasant, e. g,, weak sounds and faint lights, the tickling from delicate contact, etc. Weber's Law. — Exhaustive experiments have revealed a very interesting law, known after its first careful investigator as " Weber's Law," which obtains among the relations of these sensation intensities, as we experience them. When we place a weight of 20 grams upon the hand, we find that we observe no change in the pressure sensation until a whole gram has been added to the 20. If we take 100 grams, we must add 5 grams before we can observe the change in inten- sity; and, speaking generally, whatever absolute weight we start with, we find always that we must add the same fraction SENSATION 147 of its own weight, that is, 1-20, in order to feel that the pressure has changed. A similar thing holds true of the intensity of sounds, but in this case the fraction is approxi- mately 1-3. In sensations of brightness the change must be 1-100, etc. In all these cases the formula is most nearly true in the medium ranges of intensity. A\Tien we approach the limen or the upper limit, the relations seem to become irregu- lar, and in the case of certain senses, like smell, the appli- cation of the law is somewhat dubious. Duration of Sensations. — We have seen that every stimulus must possess a definite intensity before it can give rise to a sensation; and it is even more obvious that every such stimu- lus must also possess a certain duration, if it is to be felt. Moreover, many sensations are very profoundly altered by prolonged duration. Thus, colour sensations will be found to grow dim and to fade, if long continued. Some sensations of sound, on the other hand, seem to become more intense, if continued, and finally occasion pain. The detailed facts about the influence of duration upon sensory processes cannot at present be both accurately and briefly set forth, and we shall therefore pass them by. Extensity in Sensations. — Certain sensations, like those of vision and touch, always possess, in addition to the pre- viously mentioned characteristics of duration and intensity, a definite quality of extensity. Some distinguished psycho- logical authorities insist that all sensations are thus extensive or voluminous, sensations of sound and smell and taste, as well as those of touch and sight. This is not, however, the prevalent view, and we shall not discuss the matter here. It will be considered in the chapter on space. Suffice it to say, that a colour sensation cannot exist at all without being experienced as possessing extensity. The same thing is true of pressure ; and, in general, all sensations which ever possess the quality of extensity always possess it, Just as they possess duration and intensity. The kinsesthetic sensations are 148 PSYCHOLOGY admitted by all psychologists to belong, with pressure, tem- perature, and vision, to the spatial senses. The Attributes of Sensation. — If we bring together the points we have gone over in discussing the quality, extensity, duration, and inten3ity of sensations, we shall see that quality is, in a definite sense, the most fundamental thing about a sensation, and that the other characteristics can fairly be regarded, for our psychological purposes, as subordinate attri- butes of quality. Thus, a given musical tone may last one second, or three, without essential change in the pitch, which is its quality, psychologically speaking. It may be louder, or softer, without changing its pitch. Furthermore, it may change its timbre, which seems to be a sort of secondary- quality, by changing its overtones, and still retain its pitch, or primary quality, unaltered. Similarly, a sensation of red may come from an object one inch square, or from one two inches square, without noticeably changing the hue of the colour, although if it be made sufficiently small, the colour cannot be detected. Kevertheless, it must be recognised that if any one of these attributes becomes zero, the whole sen- sation disappears. A sensation lacking either duration or intensity, for instance, is no sensation at all. The term 'attribute' is consequently not without ambiguity in this con- nection. Functions of Sensory Processes: (1) Instigation of Move- ments. — From the physiological side it is evident that the primary organic function of the sensory processes must be that of instigating movements. In chapter III, we exam- ined certain typical instances, in which we found these proc- esses operating to produce movements, and then further operating to report the results of the movements, thus assist- ing in the establishment of useful coordinations. When we say that sensory stimulation instigates movements, we must not make too sharp a distinction between the stimulation, as sensed, and the movement, when a response is made with- SENSATION 149 out deliberation. The nervous process is practically a con- tinuous progress of impulses from the sense organs clear around to the muscles. There is nowhere any essential break in this feature of the activity. The act is literally a unit. Similarly^ if we examine the facts closely, we shall see that on the psychological side the sensory reaction is simply the registration in consciousness of a certain kind of act, and that it varies markedly with the sort of response that is executed by the muscles. A sensation of a disagreeable odour produces not only consciousness of a certain kind of olfactory quality; it produces also the consciousness of tendencies to movement, e. g., choking movements in the throat, violent expiratory movements, movements of the head away from the source of the odour, etc. The sensation of the odour is instantly merged with other sensations which these move- ments call out, and is markedly modified by them. Further- more, the kind of sensation which we get from an odour in the first instance will be determined intensively at least by the kind of movement in progress at the moment when we come into contact with the stimulus. If we are not expecting the odour, our breathing may be free and deep. In consequence, we obtain a deep inhalation of the noxious fumes, and from the blending of this impression with the ongoing mental activity, one kind of sensation results. If we are expecting the odour, or if our breathing happens momentarily to be superficial, the sensation is much modified and weakened. So we see that our consciousness of sensory stimuli is quali- fied on both sides by movements, i. e., by those movements which lead up to it, and by those which follow it. (2) Source of the Material of Knowledge. — Many psy- chologists define sensation as the consciousness of the quali- ties of the objects (including the tody) stimulating the sense organs. These qualities which we have been describing in the present chapter, e. g., redness, blueness, warmth, and cold, are highly abstract affairs isolated by us for our psychological I50 PSYCHOLOGY purposes from the larger matrix of actual conscious 6'ii:peri- ence of which they form a part. But as a matter of fact when our sense organs are stimulated, we are commonly con- scious of objects rather than of mere qualities. The con- sciousness of objects, or 'thinghood' is technically called perception and will be studied in the next chapter. James has hit off the point, in one of his happy inspira- tions, sajdng that sensation gives us mere "acquaintance with objects,^' whereas perception gives us "knowledge about" them. As a matter of fact, it is clear that our sensory experi- ences which involve simply becoming acquainted with objects are few and far between. The all but universal reaction is one in which we place, or classify, or recognise, the stimu- lus in some way, thus relating it vitally to our past knowl- edge. A literally pure sensation would only be possible as a first experience prior to all other experience. On the other hand any sensation may be regarded as elementary which cannot be further analysed. It should be added, too, that the assignment of objective character to our sense experiences is especially prompt and convincing in those senses which most definitely contribute to our awareness of extension, resist- ance, and externality to the organism, i. e., touch and vision. Despite their abstract and unreal character when taken in isolation, sensations furnish us the basic material upon which our world of knoMdedge rests. We clothe them with meaning and with associations of innumerable sorts, and in the perceptual and ideational forms, which we shall encounter in our further study, we employ them as the foundation for all our thinking. From both the psychological and physiological sides there- fore, sensory processes are fundamental. CHAPTEE VI PEECEPTION" Perception, Sensation and Ideation. — Perception has some- times been defined as "a consciousness of particular material things present to sense." Perception is as a matter of fact always a larger thing than this definition would imme- diately imply; because we are always aware in the "fringe," in the background of consciousness, of sense activities other than those we speak of as being perceived, especially those connected with the internal operations of our own organism. Perception as psychologists describe it, is therefore, like sen- sation, something of an abstraction.* Our definition, however, marks ofE perception from sensa- tion in its emphasis upon the consciousness of objects, or things. Sensation, as we saw in the last chapter, is more appropriately conceived as concerned with the consciousness of qualities. The two processes have this in common, that both are produced by the stimulation of a sense organ. This circumstance serves to mark both of them off from such men- tal conditions as memory and imagination, in which our consciousness may equally well be engaged with objects. They are probably more apt to lead to immediate motor reactions than these latter ideational processes. ISTevertheless, it seems * It will be seen from this definition that the psychologist uses the term perception in a somewhat narrower sense than that recog- nised in ordinary usage. We speak in common parlance of per- ceiving the meaning of a theory, when we refer to our appreciation, or apprehension, of it. In such cases we may be engaged in reflection upon the theory, and our thought may thus be quite independent of any immediate stimulation of sense organs. 152 PSYCHOLOGY possible, as we shall see more fully in later chapters, that the sensuous material of perception and imagination and memory is qualitatively one and the same. Visual mental stufE, for example, whether perceptually or ideationally produced, is sui generis, and totally unlike any other kind of mental stuff, such as auditory or olfactory. It will he seen that the radical distinction above mentioned between the perceptual consciousness of objects and such con- sciousness of them as we may have in memory and imagina- tion rests upon a physiological basis, i. e., the presence or absence of sense organ activity. The only difference on the mental side is commonly to be found in the intensity and objectivity of the two. Perceptions are ordinarily more intense, and feel more as though given to us, than do our memories or imaginings. Nevertheless, there are many per- sons whose imagery frequently takes on an almost perceptual vividness and is followed by motor consequences such as nor- mally belong to sense stimuli. The thought of blood, for example, or the description of a wound will in these cases elicit the most life-like visual images followed by nausea and even vomiting. In hallucination, too, it seems as though mere mental images assumed the vividness and externality of per- cepts; and in the case of very faint stimulations, e. g., of sound or colour, we cannot always be confident whether we have really perceived something, or merely imagined it. This principle of distinguishing the two is, therefore, not always to be depended upon. Fortunately for our practical interests, the distinction is generally valid and we do not often confuse what we really perceive, with what we imagine. It must be said that certain distinguished psychologists maintain that there is a real difference in quality between perceptual and ideational material. They base their view partly upon introspective grounds and partly upon alleged evi- dence from cases of mental disease, where the power to obtain images is lost without entire loss of perceptual capacity. To PERCEPTION 153 the author the evidence does not appear wholly conclusive for either alternative and he provisionally chooses the simpler. It may well be that the quality of the total psychical conditions is different when one is experiencing a visual percept and a visual image. The difference may well be due to changed organic conditions of some sort. But it by no means follows that the visual qualities as such differ in the two cases, other- wise than intensively. We pointed out the fact in the last chapter that, save for the earliest experiences of infancy, sensation, as a concrete mental state distinguishable from perception, probably does not occur. The great masses of our sensory experiences are, accordingly, perceptions, and it obviously behooves us to examine them with care. Analysis of Perception: A. Its Unifying Character. — ^We may evidently have perceptions which originate from the stimulation of any sense organ, and we might select an example from any sense department for analysis. Because of their importance for everyday life we may, however, profit- ably choose a case from visual perceptions for our examina- tion. Let us take the instance of our perception of a chair. AVhen our eyes fall upon such an object we instantly react to it as a single object. The reaction itself is a unifying act. Although the chair has four legs and a seat, we do not see each of the legs as separate things, and then somehow put them together with the seat, and so mentally manufacture a chair for ourselves. On the contrary, our immediate response is the consciousness of a single object. We know of course that the chair possesses these various parts, just as we know that it has various colours, and in a sense we notice these features when we perceive it. But the striking thing is, that despite the great number of sensory nerves which are being stimulated by such an object, we perceive it, not as an aggre- gate of qualities a-{-h-\-c, but as a unit, a whole, which we can, if necessary, analyse into its parts. There is on our part 154 PSYCHOLOGY a certain unity of interest in the thing which binds its mem- bers into a single whole. The same thing is true as to our perception of words. We naturally see them, not as so many separate letters, but as wholes> or at most as groups of sylla- bles; a fact which modern education wisely takes advantage of in teaching children to recognise entire words at a glance. Evidently this is another phase of the fact which we noted at the time v/e were studying attention, when we remarked the selective and synthesising nature of the mind in its operation upon sensory stimuli. We also came across the same fact in our description of the action of the cortex of the cerebrum. We observed there, that the cortex has its activity determined, now from this sensory source, and now from that, but the response is always of a unifying, synthe- sising character. This seems to be the reason, too, that our perceptions are so regularly definite, instead of vague, as they apparently might be. The cortical reaction tends toward the systematised orderly form. We note first, then, in our analy- sis of visual perception, that we commonly perceive objects as single and distinct, not as vague, confused, and aggregated compounds. B. Part Played by Experience in Perception. — If we describe for ourselves just what we perceive in such a case, we should add to our consciousness of the colour of the chair our sense of its size and its shape. We say, for example, that the seat is square, that it looks square. Now it requires only a moment's reflection to convince us that, as we stand at a little distance from the chair, the image of its seat, which is reflected upon the retina, is not square at all, but is a kind of rhomboid, with two acute and two obtuse angles. We become more clearly aware of this fact when we attempt to draw the chair as it appears. We are obliged under these conditions to draw just such a rhomboid as the seat presents to the eye. If we draw a real square on the paper we cannot make it serve acceptably for a chair seat, PERCEPTION 155 seen as we now see the chair of our illustration, which is supposed to be at a little distance from us. Now, how does it come about that we can perceive a rhom- boid as a square, which is what we unquestionably do in this case? The reply contains the secret of the fundamental fact about all perceptions. We see it as a square, because we see it, not as it actually is to our vision at this moment, but as our past experience has taught us it must be. Were it not for the influence of this past experience, this habitual reaction upon objects like the present chair seat, undoubtedly we should not see it as a square. The same thing is true as regards our perception of the height and size of the chair, and the material of its construction. Had we no previous experi- ences that resembled the present one, we should be hopelessly uncertain as to the element of size. To judge of this with any accuracy we must, to mention only a single circumstance, know with considerable exactness the distance of the chair from us ; for the nearer an object is, the larger our visual image of it. Experience has taught us the common size of chairs and tables, and has taught us to allow correctly for the effects of distance, etc. We come at once, then, upon this striking fact, that in some manner or other perception involves a rudimentary reproductive process. Somehow, our former perceptions are taken up and incorporated into our present perceptions, modifying them and moulding them into accord with the past. Moreover, if we interrogate our consciousness carefully, we shall find that in visual perceptions we often, perhaps gen- erally, get an immediate impression of the contact values of the seen object. We get instantly something of the cool- smooth-feeling when we look upon highly polished marble. Velvet seen near at hand gives us similarly a feeling of soft- ness. It is not simply that we know the marble to be cool and smooth, or the velvet to be soft. That would be merely a matter of associating certain ideas with the percept. We 156 PSYCHOLOGY mean to designate a phase of the actual perceptual synthesis. Individuals vary greatly as regards the manner and the degree in which these secondary sensory implications are experienced. Certain bizarre forms of a similar process, known as synses- thesia, illustrate the point in an extreme way. For example, certain persons when they hear music always experience colour sensations accompan3dng it. We may regard it as certain, therefore, that sensory stimuli affecting only one sense organ may set up perceptual reactions involving directly more than one sensory area in the cortex, so that the percept result- ing may be regarded as a coalescence of several different sense qualities. Auditory perceptions show just the same influence of experi- ence as do the visual perceptions which we have analysed. When we first hear a foreign language spoken, it is a mere babel of sounds. Presently, as we come to learn the lan- guage, the sounds become words with meanings intelligible to us, and our perception of what we hear thus manifests, as in the case of vision, unmistakable dependence upon our past experience. So also with touch. We learn that certain kinds of contact experiences mean door-knobs, or pencils, or books, etc. We might run through the whole list of sense processes and find the same thing true in varying degree. We may conclude then, that a second important factor in perceptual processes, in addition to the tendency to perceive objects as definite wholes, is the striking combination of the present with the past, of novelty with familiarity. Were it not for the fact that the perceived object connects itself in some way with our foregoing experience, it would be entirely meaningless and strange to us. This is the way the words of an unknown language impress us when we hear them. On the other hand, the perceived thing is in some particulars dif- ferent from these previous experiences, otherwise we could not distinguish the past from the present. Perception is, then, evidently a synthetic experience, and the combination PERCEPTION . 157 of the new and the old is the essential part of the synthesis. This process of combining the new and the old is often called apperception. In perception, therefore, the raw material supplied by the several senses is taken up into the psycho- physical organism, and there, under the process of appercep- tion, given form and meaning by its vital and significant union with the old psychophysical activities. Material taken up in this way becomes as truly a part of the organism as does the food which enters the alimentary tract. Genesis of Perception. — It is evident from the facts we have examined in the immediately preceding paragraphs, that the development of perception depends upon the degree to which our past experience enters into the results of each new sensory excitation. In the discussion of habit and of atten- tion, we observed that the mind undoubtedly does make itself felt, first in splitting up the undifferentiated, vague con- tinuum of consciousness into parts; then in connecting these parts with one another ; and finally in endowing the organism with habits whereby it may the more promptly and efficiently cope with the conditions it has to meet. Clearly, a fully developed perception is itself simply a kind of habit. That I should be able, when looking at a plane surface limited by four lines making two acute and two obtuse angles, to see a square table-top is only explicable by remarking that this perception has been acquired just as most other habits have been, i. e., slowly and by dint of many repetitions. So far as we can determine, experience begins to operate upon our sensory excitations at the very outset of life, and the process of perception accordingly begins, but in a very rudi- mentary manner, immediately after the hypothetical "first moment" of sensation to which we referred in the previous chapter. ISTevertheless, we must suppose that for many weeks the perceptual process is on a very low level of advancement. In the first ^lace, as we pointed out, a perception involves our having some knowledge, however simple, about the object. 158 ■ PSYCHOLOGY But such knowledge about objects depends uj)Oja. our ability to connect various sensory experiences with the same object, and this in turn depends largely upon our ability to control our movements. We mentioned in an earlier chapter that such control is a relatively late acquirement, and accordingly our perceptual processes get no available opportunity for develop- ment in early infancy. An illustration will make this clearer. Let us take the possible course of events involved in a baby's acquiring the perception of a bell. Obviously the visual factors involved cannot be satisfactorily employed, until some control has been attained over the eye muscles, so that the child's eyes are able to converge and follow an object. This attainment is commonly achieved about the third or fourth week of life, although there is great variation here. If the child never touched the bell and never heard it, he might still learn to recognise it when he saw it, as something he had seen before ; but he evidently would have no such per- ception of it as you and I have. As a matter of fact, the bell will be put into his hand, and during the random move- ments of the hand his eye will sometimes fall upon it. The occasional repetition of this experience will soon serve to fix the association of the touch-hand-movement feelings with the visual consciousness of the bell, so that the thing seen will inevitably suggest the thing felt and moved, and vice versa. Moreover, all the time this has been going on there ^ have been sensory stimulations of sound from the bell. This group of elements, therefore, becomes annexed to the rest of the group, and straightway we have the rudiments of the process by which, when we see or touch or hear a certain kind of object, we promptly perceive it as a bell, i. e., as a something to which a certain total mass of familiar experi- ence belongs. Such a case as this is t3rpical, and despite certain omissions of detail, may serve to represent the kind of activities which always accompany the acquiring of perception. Obviously PERCEPTION 159 the perceptual process involves the establishment of rela- tions. In the case which we have used for our illustration these relations show clearly in the connecting of one group of sensory experiences with, another. The auditory group comes to mean the eye group, and both of these come to mean the hand-movement group. Moreover, the definite establish- ment of these relations is practically dependent upon the motor factors by which the hand and eye come to control the object. When such relations as these are once set up, we have a definite perception of an object about which we know something, i. e., that it is an object from which we can get certain kinds of familiar experiences. It will be seen at once that in this series of events by which the perception becomes definite, the several steps involved are brought about on the strictly mental side by the activities involved in attention, which we have previously sketched. First, there is the dissociative process, throwing out into the foreground of consciousness the visual characteristics of the bell, as distinguished from other things in the visual field. This is followed by the associative, or relating process, which connects this visual bell with the auditory and tactual- motor experiences. It remains, then, to inquire what further development takes place after the accomplishment of this synthesis of the different sensory activities of sound, sight, and touch into the consciousness of a single object. Perception and Habit. — We spoke of fully developed perceptions a moment ago as habits. If this metaphor were entirely appropriate, it might seem that perceptions would come to a certain point of development and then stop. Clearly, our reference to habit was in one particular misleading. Our most perfect habits are all but unconscious. A perception, on the other hand, is distinctly a conscious process. The truth of our statement lies in this fact, i. e., that we tend to become unconscious of objects and to react to them in accordance with the principle of mere habit, just in the degree in which l6o PSYCHOLOGY our necessities permit us to perceive and react upon them in literally the same manner, time after time. We thus become almost wholly oblivious to the exact appearance of a door- knob which we have occasion to turn very often. Our eyes may rest upon it momentarily, but only long enough to guide the hand in its movement, and often without registering any visual impression of which we could immediately afterward give an exact account. There are also certain features of the neural process in perception which warrant our com- parison with habit, and to these we shall come in a moment. The great mass of our perceptions, however, are of objects whose relations to us change sufficiently from time to time to make any complete subsidence of our consciousness of them incompatible with their effective manipulation; consequently we continue to be definitely aware of them. Development of Perceptual Process. — The development of perception, which goes on in a certain sense more or less all our lives, and in a very definite sense up to the period of mental maturity, is plainly not a development involving simply a more automatic response to objects. Quite the con- trary. The process which we commonly think of as growth in the powers of perception consists in the further elabora- tion of our discriminative and associative activities. We learn to see new things in the old objects, new characteristics, which before escaped our knowledge. We also learn more about the objects, and thus, when we perceive them, perceive them in a modified and more intelligent way. Speaking literally, it therefore appears that development in perception really involves perceiving new objects in the old. A moment's reflection will show the similarity of this fact to one which we noted when analysing attention, i. e., that to continue our attention to an object for more than a moment, we must notice something new about it, see it in a new way. We might of course substitute the word perception for the word attention, inasmuch as attention is an attribute of all PERCEPTION i6i consciousness, and then the proposition would read: we can- not continue to perceive an object beyond a moment or two, unless we perceive it in a new manner. Perceptions which we do not execute in a new way, we have already seen do actually tend to lapse from consciousness, passing over into habits of response which we make to certain physical stimuli. When a child is taught to observe the arrangement of the petals of a flower, he henceforth perceives the flower in a new way. To him it really is a new object. All development in perception is of this kind, and constitutes a sort of trans- formation by the unfolding of the old object into the new and richer one. The larger part of this perceptual develop- ment occurs during childhood and adolescence. Neverthe- less, there is a continuation of the process in an inconspicuous way far into old age. Thus, we come in childhood to recog- nise the salient characteristics of the common things about us in every-day life. During adolescence we enrich this material by observing more accurately the details of these things, and by increasing our knowledge of their general purport and relations. After attaining maturity our further advance is almost wholly connected with the affairs of our professional, or business, life. The musician becomes more sensitive to the niceties of harmonic accord and the nuances of melodic sequence. The business man becomes more observant of the things which pass under his eye, so far as they are related to his specialty. The elementary school teacher learns how to keep the corner of her eye sensitive to iniquity upon the back seat while apparently absorbed in listening to the recitation of virtue upon the front bench. The mother learns to watch her children with an increasingly intelligent discrimination between acts which indicate illness and those which indicate fatigue, excitement, and transitory irritation. Everywhere development is primarily shown by fresh skill in the detec- tion of new features in old things. Illusions. — Certain instances of illusion furnish a striking i62 PSYCHOLOGY confirmation of the general idea of perception which we have been explaining. An illusion is a false^, or erroneous, percep- tion, which is often spoken of as a deception of the senses. But this is often misleading, as we shall presently see, for the senses frequently operate properly enough. The difficulty is with our reaction upon the sensory material furnished to us. Indeed, there is undoubtedly a measure of illusion in most perception, but unless it is sufficiently significant to cause practical difficulty, we entirely overlook it. Among the most frequent of such illusions is the misread- ing of printed words. We sometimes read the words put before us as we have reason to suppose they ought to be, not as they are. Thus, if we come across the word mispirnt, many of us will read it in all good faith as misprint and never see the difference. We react to the general visual impression and its suggestion, and we see what really is not before us. If the sentence in which the word occurs is such as to give us a definite anticipation of the word, the probability of our over- looking the typographical error is much increased. Similarly when we come into a darkened room where sits a spectral form — an experience which as children most of us have had — we see a person with startling clearness; and the subsequent discovery, that the supposed person consists of clothing hang- ing upon a chair, is hard to accept as true. Illusions of sound are very common. We fancy we hear our names called, when in point of fact the sound we thus interpret may have been anything from a summons to some other person of simi- lar name, to the barking of a dog, or the whistle of a locomo- tive. Tactual illusions are also easy to produce. The so-called "illusion of Aristotle" is a good specimen. (Figure 51.) Children often achieve it by crossing the first and second fingers, and then moving to and fro upon the bridge of the nose with the crotch thus formed between the fingers. Presently one becomes distressingly impressed with the fact that one possesses two noses. PERCEPTION 163 The Causes of Illusions : A. Central Interpretative Factors. — This last instance is typical of many illusions, in that it is caused by stimulating with a single object the sides of the two fingers which are not ordinarily in contact with one another, and for the stimulation of which, accordingly, two ob- jects are commonly necessary. We react in the familiar, the habitual, way to the simul- taneous stimulation of these areas of the skin. This has tt ct riG. 51. invariably been accomplished hitherto by the pressure of two objects, and two objects we therefore feel. It is clear that in such a case the sense organ is in no way at fault. It sends in the impulses communi- cated to it just as it has always done before; but the reaction which we make upon the impression also follows the usual course, and in this special case happens consequently to be wrong. The same explanation applies to our reading of incorrectly spelled words. Many illusions of movement, e. g., such as we obtain in railroad trains, are of this character. The same general principle holds, but applied in a slightly different manner, when we see, or hear, or otherwise perceive, some object not actually present, because we are expecting to perceive it. Thus, if we are listening for expected foot- steps, we find ourselves time after time interpreting other sounds as those of the awaited step. At night the nervous housewife wakens to hear the burglars passing from room to room along the corridor. Step follows step in stealthy but unmistakable rhythm, though the whole impression has no other objective basis than the occasional cracking of floors and partitions, phenomena which are the constant accom- paniments of changing temperature. Illusions of this sort are readily induced if we have recently had experiences which might suggest them. Recency of similar experience has, then, Fig. 52. 164 PSYCHOLOGY to be added to expectancy and liabit as a possible source of illusory perception. It is clear tbat a consideration of certain types of illusion affords new and striking confirmation of the part played in perception by previous experience. The cortical reaction suggest- ed by the stimulus does not happen to correspond to the object actually present. But this corti- cal reaction is evidently determined by the impress of old perceptual experiences whose traces have been preserved. The same point is admirably illustrated by such drawings as the accompanying, figures 52 and 53. We can see the stairs, either as they appear from above, or from below. In one case the surface a seems nearer to us; in the other case 6 seems nearer. We can see in the other figure a big picture frame, the frustrum of a pyramid, or the entrance to a square tunnel. Yet one and the same object is presented to the retina in each case. The eye can hardly be accused of entire re- sponsibility for the shifting re- sults. But lines like these have actually been connected in our former perceptions with the several objects named, and in consequence the cortical reaction appropriate to either of them may be called out. It would seem abundantly certain, therefore, that wliile a portion of what we perceive is always supplied from without, another portion, and often the dominant por- tion, is supplied from within ourselves. \~7 Fig. 53. PERCEPTION 165 B. Peripheral Factors. — There are many kinds of illusions, be it said, which do not come immediately under the head- ings we have discussed. For example, such illusions as that in figure 54 are much too complex in their basis to be prop- erly included, without modification, under the explanatory rubrics we have considered. The innervation of the eye muscles is probably an influential element in many illusions of this character. In the upper figure the short angular lines carry the eye in large sweeping movements out beyond the main line, whereas in the lower figure these movements Fig. 54. Despite their contrary appearance, the two horizontal lines will be found of equal length, tend to be checked by the recurrent angular lines. Even though the eye does not make a very different excursion in the two cases, we notice a distinct difference in the seem- ing magnitude of the movements and this difference is natu- rally transferred to our judgment as to the extent of the lines. In certain forms of this type we sometimes find that there is a suggestion of an enclosed figure, which in the case of the lower of these particular figures is evidently smaller in its horizontal dimensions than that of the upper figure. Photo- graphs have been made of the eye while observing illusory figures of many sorts and from these it is perfectly obvious l66 PSYCHOLOGY that while the eye seldom follows precisely any of the lines of a figure, nevertheless the movements which are actually executed vary greatly in dependence upon the position of the various lines which make up the figure in its entirety. Where these movements involved in perceiving are very different, it is to be expected that our judgments of the space rela- tions of the objects perceived should also vary. Probably the actual conformation and the muscular mecha- nism of the sense organs, especially the eye, may be immediate causes of a number of illusions. The tendency to see a vertical line as longer than a horizontal line of equal length has been regarded as an instance of this sort, because more muscles are involved in vertical movements and therefore pre- sumably more complex innervation is required. We judge that line longer which requires the greater effort to traverse. To make clear other cases of this kind would require more space than can properly be given here. Certain it is, however, that we perceive all objects in ways which vary with their surroundings. We noticed in the chapter on sensation that colours are seen very differently when combined with differing companions. Eed seen beside yellow looks quite different from red seen beside blue. A sound seems much louder if heard in the midst of quiet than if heard amid louder sounds. Large objects are made to appear larger by contrast with very small ones. In short we perceive all things in relations which modify them and many of these modifying circumstances are primarily conditions in the sense stimuli. Hallucination. — In distinction from illusion, which is essentially perception, (i. e., a consciousness of particular material things present to sense — though other things than those really perceived happen to be present), hallucination is the name given to the consciousness of objects felt to be physically present, when as a matter of fact no object of any kind is at hand. Illusions are every- day experiences familiar to all of us. Hallucinations, while by no means infrequent, PERCEPTION ~ 167 are much less common and consequently more difficult to describe satisfactorily. Many of tlie alleged telepathic phe- nomena involve hallucinations. Thus, for instance, one is sitting alone in a room and suddenly sees another person, known to be thousands of miles distant, come in and sit down. Again, when alone in the same way, one suddenly hears some sentence clearly spoken. In neither case, needless to say, is anyone actually present, save the owner of the hallucination ; and there are no obvious external phenomena which could be held accountable for the experience. All the senses seem to be represented from time to time in the hallucinatory percep- tions, although hearing and vision are, perhaps, the ones most frequently involved. An interesting distinction has been made between true hallucination and what is called pseudo-hallucination. In the first case the perceived object not only seems external and real, but there is in the mind of the person experiencing the hallucination no suspicion at the time that the object seen, or heard, is not actually real and present. In the second form there is a sort of background consciousness, such as we sometimes note in dreams, which assures the victim that the phenomenon is after all imaginary and unreal, despite its genuinely objective appearance. It has been suggested that hallucinations are really extreme forms of illusions, extreme cases of misinterpretation of sen- sory stimuli, resting upon highly disintegrated cortical forms of reaction. The sensory source of the stimulation has been sought at times in pathological conditions of the sense organs, e. g., congestion of circulation in the eye, or ear, etc. There are many facts which tend to confirm this view, which is advocated by certain of the most competent judges; and some others which are very difficult of reconciliation with it. A discussion of the point at issue would take us too far afield for present purposes, and readers who are interested in such matters must consult some of the more extended and special- i68 PSYCHOLOGY ised treatises. Meantime, we must admit that unless tliis last suggestion is correct, hallucination furnishes an excep- tion to the general rule that cortically initiated conscious processes are less vivid and less definitely externalised than those which originate in sense organs. If hallucination is not peripherally initiated, it belongs to the group of phe- nomena which we shall examine in the chapter upon imagina- tion, and we may defer further discussion of it until we reach that point. Neural Process in Perception. — The nervous pathways involved in perception have already been described in a gen- eral way in chapter II. In vision, for example, the occipital regions in the cortex are unquestionably employed, in cases of auditory perception the temporal region is active, etc. Undoubtedly the association areas also play a very important part. Connected with their activity there is this highly important fact to be taken more explicitly into account, i. e., that in perception the cortical activity, which is in part decided by the Tcind of neural stimulus sent into it, is in large measure determined by the modifications which previous experiences have impressed upon the structure of the hemi- spheres. Evidently this is but a statement in physiological terms of the doctrine which we have already enunciated in psychological form. As we observed in our discussion of habit, every nervous current which passes through the cen- tral system seems to leave its impress behind it, and this impress modifies the nature of the neural excitations which follow it. The case of perception is, accordingly, only a spe- cial instance of this general principle, albeit a peculiarly important and conspicuous one. It is on this account, i. e., because of the fundamental importance of the accumulating modifications of the cortex, that we compared perception, earlier in the chapter, to the case of habit. From the side of neural action, therefore, perception cannot be referred simply to the employment of a certain pathway throughout PERCEPTION 169 the sensory-motor tracts; it must be referred to a certain Icind of action, in which the result in consciousness appears to be a product of two neural factors — sensory stimulus into cortex modified by previous experience. General Function of Perception: A. Its Organic Rela- tions. — In order to give perceptual processes their proper setting among the psychophysical activities of adjustment, we must revert once again to our notion of the sensory-motor cir- cuit. We have already observed that in this device the sense organs represent so many telephonic receivers ready to trans- mit inward messages from the external world to the organism. We have also described in a general way the method by which certain kinds of motor reactions to these sensory stimu- lations are brought to pass. But in the higher brain centres the pathways connecting sense organs with muscles are often extremely complex, and a stimulus transmitted inward by the afferent nerves may lead to innumerable intermediary brain activities before it issues again in movements of the voluntary muscles. Now perception is the conscious con- comitant of certain of these brain processes. Memory, imagi- nation, reasoning, etc., are others. Bearing these facts in mind, and observing closely what actually occurs when we are engaged in perceiving objects, we readily detect the main functions of perception. B. Perception as an Elementary Form of Knowledge. — Perception represents the immediate, organised, mental reac- tion of the individual upon his environment. The process is sometimes called presentation, and this is a good name for it. In it the world is presented as a system of relations — not merely reflected as a disorganised mass of atoms and molecules, but constructed by the various activities of atten- tion into definite objects. If sensation is properly described, after a common fashion, as the process in which the mind and the world of matter first come together, perception may be described as the point in which the past and the present I70 PSYCHOLOGY come together for the creation of a new object. The per- ceived thing is not simply the physically present vibrations of atoms and molecules vt^hich we call light, or sound, or what not; it is these vibration's, as they are interpreted by a psychophysical organism which exposes to them a nervous system already affected by past experiences, that enable it to get only certain specific kinds of results from the present synthesis. Evidently we make far more constant use of our past experience than common-sense observation would lead us to suppose. It is not only when we reflect upon our past life that we shape our action in accordance with its instruc- tions and admonitions; every time we open our eyes to see, or our ears to hear, what we can see and hear is in a true sense and in a large measure determined for us by what we have previovsly learned to see and hear. It is a moralistic truism that only the good can really love and appreciate virtue. But this principle is not simply, nor primarily, a moral tenet. It is based on irrefutable and unavoidable psychologi- cal foundations. It states a law of the mind which we might wish at times to change, but cannot. The first and basic function of perception, then, is to afford us our primary knowledge of a world of objects amid which we have to live., It is the first actual, definite, and complete step in the process of knowledge whose further and more complex features we have next to examine. C. Perceptual Control over Movements. — The second great function of perception grows out of the first. Indeed, it might be regarded as in a measure simply a corrolary of the first. All the sensory and afferent processes have their ulti- mate value, as we saw must be the case in chapter II., because of the more efficient movements of adjustment to which they lead. Perception is no exception to this rule. ISTow in order that sensory stimulations may not lead at once to motor responses, but may be interpreted and correlated with other sensory impulses, it is evidently necessary that there PERCEPTION 171 should be some provision for halting them momentarily, and identifying them, when they come again and again. Perception is the process by which this identification is made possible; and so it comes to pass that perception is the first, both logically and genetically, of the conscious operations by which the life of control is inaugurated. We have repeatedly seen that perception involves immedi- ately within itself the effects of antecedent experience, and a secondary result of this complication with memory processes is that when we perceive an object which is in any way familiar we instantly recognise it. If the object thus rec- ognised be one about which our previous experience is unam- biguous, we respond almost instantly with appropriate move- ments — those of aversion, if it be repulsive or harmful, those of approbation, when the contrary sentiments are aroused. If the object have no such definite antecedent reactions (whether native or acquired) connected with it, we straight- way fall to deliberating as to our course of action; or if the impression be wholly fleeting, we pass to some more stimulat- ing excitement. Perception is thus the gateway through which the mass of sensory excitations (save those already grown purely habitual) must pass before they can be permitted to set up motor responses of the volitional kind. Often the perceptual activity is sufficient to decide this volition. The clock strikes and we rise to leave the room. When mere perception is not felt to be adequate to the case, the matter is handed over to reflective deliberation. In either event, voluntary response is safeguarded. The formation of the elements of the process of knowledge and the inauguration of the control over move- ments in accordance with the mandates of experience — these are the two great functions of perception. This statement applies without modification to the special phases of percep- tion, to which we shall next advert. CHAPTEE YII PEECEPTION" OE SPATIAL AND TEMPOEAL EELATIONS I. SPACE The objects which we have mentioned in our analysis of sensory consciousness are all objects perceived by us as parts of a spatial and temporal order; and it is evident that our account of them would be extremely defective if we altogether omitted a study of these time and space relations. We shall consider space first. Two Fundamental Problems. — Psychologists are divided in opinion upon two fundamental problems concerning our space perceptions. It is maintained in the first place by some of them, the nativists, that the capacity to perceive space is an innate, hereditary trait possessed by us in advance of experience. Others, the empiricists, maintain that spatial judgments are as much the results of experience, are as truly acquired, as piano playing or the liking for caviar. We shall not discuss the question, for this would require more time than we can give it. But we may register the dogmatic opinion that both parties to the controversy are in a measure correct. We hold that the crude, vague consciousness of extension, of volume, is a genuinely innate experience, occurring at once upon the reception of appropriate sensory stimulation; and that it is underived by mere experience from non-spatial psy- chical elements. So far we are nativists. On the other hand, we are confident that practically all accurate knowledge of the meaning of the space relations in our space world, all precise SPATIAL AND TEMPORAL RELATIONS 173 perception of direction, position, contour, size, etc., is a result of motor experience, and could never be gained without it. So far we are empiricists, holding to a genetic point of view regarding the development of our adult space consciousness. Effective space perception involves not only the experience of vague extension, but also movements of localisation. In the human being there are surely but few localising move- ments which are wholly innate. The analyses and discussions which follow will serve to furnish some of the evidence upon which this view rests. Sensory Basis of Spatial Perception. — The second main point upon which psychologists are unable to agree concerns the sensory sources from which we gain our spatial judg- ments, a matter to which we made cursory reference in chap- ter "V. The majority of psychologists maintain that vision and touch are the only real avenues of spatial perception; whereas certain others, like James, boldly maintain that all forms of sensory consciousness are "voluminous," — smell and taste and audition, as well as sight and touch. The doctrine maintained in this book is that all forms of sensations are immediately suggestive of spatial attributes, e. g., position, size, distance, etc. ; but that only sight and touch possess intrinsically and completely the full spatial characteristics. We include in touch, when thus mentioned, all the cutaneous sensations and the motor, or kinsesthetic, sensations. As a matter of fact, however, the temperature and pain sensations, considered apart from pressure and sensations of movement, are ordinarily negligible elements. When involved in con- junction with pressure, they often modify our perceptions materially. Thus a cold object, e. g., a coin laid on the fore- head, often feels larger than a coin of equal size, but of the body temperature. Doubtful Cases. — Taste and smell and hearing are really the debatable sensations. Taste we throw out of court at once, because taste stimuli practically involve invariably the 174 PSYCHOLOGY stimulation of cutaneous sensations of contact and tempera- ture. We cannot, therefore, submit the matter to unam- biguous introspective analysis. Smells we undoubtedly classify at times in ways suggesting spatial attributes, and by turning the head until we determine the direction of maximum intensity we undoubtedly localise them roughly. The smell of illuminating gas seems somehow a more massive, extensive sort of thing than the odour of lemon peel. But if one lessens the disparity in the intensity of the two odours, by getting just the merest whiif of the gas and inhaling freely and deeply of the lemon odour, the spatial difference between the two begins to evaporate. There can be no question but that we tend to think of the more intense and more widely diffused odour as the larger. Nor is this remarkable, since we find it actually occupying more of the atmospheric space about us. But when we note that with mild intensities of odours their spatial suggestiveness wanes; when we further note that we have no definite impressions of size, much less of shape, under any conditions; and finally when we remark that even our ability to localise odours is extremely imperfect, we may well question whether smell has itself any properly space quality. The case of auditory space is similar to that of smell. We are told, for instance, that the tones of the lowest organ pipes are far larger, far more voluminous, than those of the high shrill pipes. A base drum sounds bigger than a penny- whistle, a lion's roar than the squeaking of a mouse, etc. Such illustrations, when adduced as evidence of the spatial character of sounds, evidently contain three possible sources of error. In the first place, we often know something about the causes of these sounds, and we tend to transfer the known size of the producing object to the supposed size of the sound. Secondly, and of far more consequence, sounds affect other organs than those of the internal ear, especially when they are loud or of deep pitch. Powerful tones thus jar the whole SPATIAL AND TEMPORAL RELATIONS 175 body, and are felt all over. Moreover, vibrations of the drum membrane of the middle-ear undoubtedly set up crude sensa- tions of pressure, or strain, to which we may come to attach a spatial significance associated with the sound. Add to this, thirdly, the fact that we readily convert judgments based upon the intensity of sounds into judgments about their extensity, just as in the case of smell, and one has a large mass of considerations leading to scepticism concerning the genuineness of intrinsic auditory space relations. Of course, no one doubts that we localise sounds, and of the factors involved in this process we shall have more to say presently. But the fact that certain sounds are located within the head (e. g., when two telephone receivers are placed against the ears and an induction shock sent through them) has been cited to prove the native possession of a true auditory space; for here apparently experience from the other senses, such as vision, would give no direct assistance. But these cases are certainly capable of explanation by means of the intra-cranial sensa- tions set up in pressure nerves by bone vibrations, and by the effect of the imagination, visual and otherwise. Taken alone, such evidence could hardly be conclusive. If we come back, then, to ordinary introspection, we find that all which the most ardent partisans of an auditory space can claim is a much emaciated form of the visual and tactual article. A vague sense of volume, or mass, much vaguer even than that given by mere temperature, with some crude sense of position, would seem to be the utmost capacity. Any sense of contour or shape or exact size, any ability to measure, is lacking. Clearly such a space, even if genuine, which we doubt, would ill deserve to be ranked beside the space of eight and touch. The manner in which we localise sound may best be described after we have analysed visual and tactual space. Growth of Space Perception. — Our adult cognition of €pace relations is generally so immediate and unreflective, the 176 PSYCHOLOGY feeling for space values so compelling and seemingly inevit- able, that we find it difficult to believe that these reactions are the results of a slow process of growth and learning. Nevertheless, this is unquestionably the fact. Babies evi- dently have no precise perceptions of space until they have acquired a considerable degree of motor control; and even then their appreciation of large expanses and distances is often ludicrously inexact. The child reaching in good faith for the moon is the stock illustration of this sort of thing. That we have no precise appreciation of visual space relations until experience has brought it to us is abundantly proven by the cases of persons born blind and successfully operated upon for the restoration of sight. Immediately after the operation such persons are almost wholly at a loss for accurate impres- sions of size, shape, or distance. After the hands have explored the objects seen, and the eyes have been allowed to pass freely to and fro over them, these spatial impressions gradually be- gin to emerge and take on definiteness. By the use of properly arranged lenses and prisms experiments of various kinds have been made on normal persons, showing that we can speedily accommodate ourselves to the most unusual inversions and distortions of our visual space. We can thus learn to react properly, although all the objects, as we see them, are upside down and turned about as regards their right and left rela- tions. The new relations soon come to have the natural feel- ing of ordinary perceptions. These observations show very strikingly that our space perceptions are functions of experience and can be changed by changing the conditions of the experience. Moreover, it is easy to demonstrate that the space relations, as we perceive them by different senses, are far from homoge- neous. Indeed, the impressions which we gain from the same sense are often far from being in agreement. N"ever- theless, we feel our space relations to be objectively homo- geneous, a result which could hardly come about under such SPATIAL AND TEMPORAL RELATIONS 177 circumstances of sensory disparity without the harmonising effects of experience. To illustrate — the edge of a card pressed gently upon the forearm will feel to the skin shorter than it looks. The same card, if the finger tip is allowed to run slowly along it, will feel longer than it looks. The dis- appointing disparity between the cavity of a tooth, as it feels to the tongue and appears to the eye or feels to the finger-tip, is a notorious instance of the same thing. The tongue and the finger-tip both give us pressure sensations. Yet they give a very different report of the same object. Similarly, objects seen upon the periphery of the retina appear smaller than when seen by the fovea; and often they undergo a certain distortion in form. That we should per- ceive, amid all these possible sources of confusion, a fairly stable and well-ordered space world betokens unmistakably the systematising effects of experience, controlled no doubt by the exigencies of our practical interests in effective orientation. Part Played by Movement. — Even though we recognize the fact that experience brings order and precision and effective- ness into our space perceptions, the general manner by which these results are achieved is not yet clear; much less what factors are chiefly employed in their attainment. It requires only the most cursory examination to convince one- self that the all-important element in the building up and correlating with one another of our various spatial sensa- tions is movement. In acquiring accurate touch perceptions, for instance, the finger-tips and hands move over the object, grasp it now in this way and now in that, until a complex set of tactual impressions has been gained from it. Without such movement our touch perceptions are vague in the extreme. If we close our eyes and allow another person to put a series of small objects upon our outstretched hands we receive only the most indefinite impressions of form and size and texture. But allow us to manipulate the same objects in our fingers, and we can give a highly accurate account of 178 PSYCHOLOGY them. Similarly, if we wish to compare visually the magni- tude and contours of two objects, we must allow our eyes to move freely from one to the other. Indeed, reflection must assure us that the vital meaning of all space relations is simply a given amount and direction of movement. To pass toward the right means to make a certain kind of movement; to pass upward means to make another kind, etc. To be sure, we assign arbitrary measures to these relations, and we say an object is a mile away, or is a foot thick and six inches high. But the meaning to us of the mile, the foot, and the inch must always remain ultimately expressible in movement. Were it possible to get at the exact stages in the process by which the child acquires its control over space relations, we should thus secure the most penetrating possible insight into our adult space perceptions. But as this is at present impracticable, we must content ourselves with an analysis of the factors which seem clearly involved in these adult con- ditions, without regard to their genetic features. Touch and Vision. — It is certain that touch and vision practically cooperate from the beginning, and we shall isolate them from one another only to point out their respective peculiarities, and not because their operation is independent. The most important, and for practical purposes the most accurate, part of our touch perceptions comes from the hands and finger-tips. By moving the hands over the various parts of the body we come to have a fairly accurate notion of their touch characteristics in terms of the hand as a standard. Moreover, each hand touches the other, and we thus get a kind of check from touch on the tactual standard itself. Generally speaking, when two parts of our body touch each other we feel the one which is quiet with the one which is moving. Thus, if we stroke the forehead with the fingers we feel the forehead ; but if we hold the hand steady and move the head, we feel the fingers. 'Now in order that we should be able to learn in these ways that a certain amount of sensation SPATIAL AND TEMPORAL RELATIONS 179 in the finger-tips means a certain area on the forehead, and, much more, that we should be able to tell with so much accuracy when we are touched what part of the body the sensation comes from, seems to depend upon what Lotze calls the "local sign." Local Signs. — If one is touched upon the palm and upon the back of the hand, one obtains from both stimulations sensations of pressure; but however much alike they may be as regards duration, intensity, and extensity, we promptly feel a difference in them, which leads us to refer each to its appropriate region. E"ow this something about touch sensa- tions which permits us to recognise them as locally distinct, although we recognise all of them as being cases of contact, is what is meant by the local sign. These local signs, then, are the relatively fixed elements in our space-perceiving proc- esses. It is by learning to correlate one group of them with another group that we can develop by experience the accuracy of our perceptions. Thus, for example, we come to learn that the stimulation of one series of local signs in the order a-i-c means a special movement of one hand over the other, say the downward movement of the right hand over the left. The same series stimulated in the order c-h-a means the reverse movement. It must be remembered very explicitly at this point that we are including the kinesthetic sensations of movement under the general heading of touch; since we doubtless have local signs of movement distinct from those of the cutaneous pressure sense, and they doubtless play a very important part here. But they are commonly fused in an inextricable way with the pressure sensations, so that a separate treatment of them seems hardly necessary in a sketch of this kind. A Caution. — A warning must be held out at this point against the fallacy of supposing that in learning his space world a child uses these local signs in any very reflective way. He does not say to himself: "That movement of l8o PSYCHOLOGY localisation was inaccurate because I used the wrong local sign to control it." He generally employs the "try, try again method/' until he hits the mark. But his success carries with it a recollection of the total feeling of the successful experience, and in this total feeling the local sign element is an indispensable part, even though the child is not himself definitely cognisant of the fact. The simultaneous stimulation of a group of these local signs gives us the extensity feeling of touch, and when the impressions come from three-dimensional objects we get, through our motor reactions upon them, experiences of change of motion in three cardinal directions. This seems to be the basis of our tactual tri-dimensionality. Delicacy of Touch. — In normal persons touch falls far behind vision in its spatial nicety of function, and far behind its possible capacities, as is shown by the astonishing accuracy of blind persons, who do not, however, seem to be notably more accurate than seeing persons as regards the parts of the body which are not used for tactual exploration, e. g., the forearms and the back. But despite its lesser delicacy, touch- movement undoubtedly plays an important role during child- hood in furnishing interpretative checks upon our visual estimates of large areas and great distances. The visual per- ception of a mile, for instance, gets a practical meaning for us largely through our walking over the distance. More- over, although vision so largely displaces touch in our actual spatial judgments, touch always retains a sort of refereeship. When we doubt the accuracy of our visual perceptions we are likely, whenever possible, to refer the case to touch, and the verdict of this sense we commonly accept uncritically. Peculiarities of Vision.- — Vision resembles the non-spatial senses of smell and hearing in one particular which marks it off characteristically from touch. Touch sensations we commonly refer to the surface of the body itself, although when we tap with a cane, or a pencil, we seem to have a SPATIAL AND TEMPORAL RELATIONS l8l curious kind of projection of part of our sensations out to the farther tip of the object. Visual objects we always place out- side ourselves. Even our after-images gotten with closed eyes often seem to float in a space vaguely external to ourselves. It seems necessary to assume a system of local signs for vision, comparable to those of touch-movement, although doubtless more complex. It must be admitted, however, that introspection is much more uncertain in its deliverances here, than in the case of touch, and we shall be on somewhat spec- ulative ground in assuming the nature of this visual local signature. It seems probable that this attribute of sensa- tions from the periphery of the retina consists primarily in reflex impulses, or tendencies, to movement toward the fovea, the fovea itself furnishing a peculiar sense quality which serves more or less as a fixed point of reference. Certain it is that stimulation of any part of the retina tends to release movements turning the fovea toward the stimulus. Moving objects are especially eflective in producing such movements. The incessant and complicated movements of the eyes over the visual field must speedily render the relation of the various retinal points as conjoined by movements, intri- cate in the highest degree. But such relations as exist must pretty clearly rest on the intermediation of movements Avith their motor and retinal effects upon consciousness; and it seems probable, therefore, that the space value of any retinal point comes to be determined by the position it occupies in such a system of movements. Thus, a point 20° to the right of the fovea in the visual field comes to mean to us a definite kind of motor impulse. One 20° to the left, another kind of impulse, etc. Whether the visual local sign is actually this sort of a fused retinal-kinsesthetic affair or not, there can be no doubt that, as adults, we have a remark- ably accurate sense of the general space relations of the objects in the field of view, and that we can turn our eyes with unhesitating accuracy to any part of this field. Moreover, lS2 PSYCHOLOGY experiments have shown that the behaviour of the eye move- ments depends upon the condition of the entire visual field. For instance, the eyes are ordinarily more stable in their muscular balance when looking at a field where a considerable complexity of detail is discernible than when the surface is plain. Their movements in dim light are much less well balanced and coordinated than in a bright light. The Binocular Conditions of Single Vision. — In the chapter on sensation we explained the processes of accommo- dation and convergence by which the eyes are turned together towards any object we desire to see and the rays of light from it focussed so as to produce a clear image on the retina. Fig- ure 55 illustrates the conditions under which we receive either single or double impressions from any given stimulus. When the fovege of the two retinae are stimulated, as in ordinary convergence upon an object, we always see a single object. If two tubes ten inches or thereabouts in length be supplied with thin white paper caps fastened smoothly over the ends, an interesting demonstration of this statement can easily be made. Upon each of the paper caps mark a straight black line corresponding to a diameter. Then hold the tubes parallel to one another in front of the eyes and look into the open ends. This will insure the stimulation of the fovea of each eye by the line across the end of its own tube. If the lines be in a position of parallelism with one another, their images will swim together into a single line. If they be held at an angle to one another, they will appear as a single figure forming a cross of one or another form. If the caps be given very different and complex figures, we shall generally see first one and then the other of the figures, but while the tubes are parallel we never see two separate objects. This last phenomenon is known as retinal rivalry. Each point on each retina has a point Iniown as its "^corresponding point" on the other retina which, if stimu- lated with it, leads to single vision. The stimulation of SPATIAL AND TEMPORAL RELATIONS 183 non-corresponding points produces double images or blurred vision, as the case may be. The legend under figure 55 will make clear the details. Fig. 55. The two lower circles represent the retinal surfaces of the two eyes as seen from behind. F is the fovea, B, the blind spot where the optic nerve enters the eye. The retinae are divided into four quadrants. Each quad- rant corresponds to its geo- metrically (not anatomical- ly) similar quadrant in the other eye, which bears the same number. The nasal half of one retina corres- ponds to the temporal half of the other, Corresponding points whose stimulation pro- duces single vision are lo- cated in geometrically sim- ilar quadrants. The stimu- lation of other than corres- ponding points leads t o either blurred or double vision. The upper part of the diagram represents the eyes fixated on the point F whose images fall on the two foveal re- gions ff and produce single vision. is the optic nerve. Rays of light from such points as E and D fall on the corresponding points ee and dd and also produce single vision. Such a line as EFD, or it may be a surface, all of whose points are seen as single, is known as a horopter. When the eyes are fixated on F, points like B and C, which lie respectively behind and in front of F, are seen double. The rays proceeding from them will be found in non- corresponding quadrants of the retinae at 66 and cc. The rays from B fall at b and 6 which are both inside the foveal points, whereas c and c are both outside these points. The former pro- duce 'homonomously,' the latter 'heteronomously' doubled images. The reality of these double images may easily be verified by holding up pencils in front of the face, one about a foot behind the other, and then fixating first on one and then on the other. The unfixated pencil will be seen double. If an assistant paas a screen in front of one of the eyes, the double image on the same side as the screen will disappear when the nearer pencil is fixated. This is the case of the 'homonomous' image. The l84 PSYCHOLOGY The Third Dimension. — Psychologists have always been especially interested in the problem of the visual perception of distance, or the third dimension. Bishop Berkeley main- tained in his celebrated work entitled "Essay Toward a New Theory of Vision" (1709), that vision cannot give us any direct evidence of distance, because any point in the visual field must affect one point and one only in the retina, and it can affect this no differently when it is two feet away from what it does when four feet away. Therefore, Berkeley con- cluded that our perception of visual distance is dependent uj)on our tactual-motor experiences. This view overlooks several important facts, including its plain contradiction of our common conviction about the matter. In the first place, we have two eyes, and each eye sees a part of solid objects vary- ing slightly from that seen by the other, as may easily be proved by looking at some solid object like a lead pencil with first one eye closed and then the other. Compare figure 55. The psychical percept of such objects appears to be a fusion of the factors supplied by the two eyes, and we get from this source the visual sense of solidity. The stereoscope employs this principle, and by giving us pictures which exaggerate somewhat the disparity in the point of view of the right and left eye affords us a most startling impression of distance and volume. If the pictures presented to the two eyes be exactly similar, we see a flat surface instead of a solid. By allowing each eye to see the side of the object ordinarily seen by the other, the pseudoscope renders hollow objects apparently solid and solid objects hollow. Furthermore, we converge our eyes more upon near points image in the side opposite to the screen {i. e. heteronomoua ) will disappear when the farther pencil is fixated. Such a figure as the prism EXD illustrates in an extreme form the facts of binocular stereoscopic vision. The right eye sees only the surface XD, the left eye only EX. The figure as seen by both eyes appears as a solid. Ordinarily there is a field comtaon to both eyes as in looking at a sphere. SPATIAL AND TEMPORAL RELATIONS 185 than upon far, and the muscular strain thus brought about may serve to inform us of differences in distance. Similarly, the muscles controlling the lenses contract with varying degrees of intensity in the effort properly to focus rays of light from objects at different distances. Monocular vision has therefore a motor index of tri-dimensional properties, but it is extremely imperfect in practical exigencies. How far our consciousness of these focussing movements is significant for our judgments of distance it is difficult to say. But it is at least clear that there are factors operative other than those Berkeley emphasised, and the genuineness of the optical sense of distance can hardly be seriously questioned. The eye is, in short, not merely a retina, it is a binocular motor organ as well. Normally, therefore, visual perceptions are always fused stereoscopic binocular-motor experiences. We use in actual practice other forms of criteria for dis- tance. Thus, the apparent size of the object is used as a clue to its distance. By the apparent size of a man we may judge whether he be a mile or a hundred yards away. Conversely, when we know the distance, we can emjDloy it to form an estimate of the size of an object at that distance. Thus, if we know the approximate distance, we can be fairly sure whether the person we see is a man or a boy. The seeming size of objects runs roughly, but not precisely, parallel with the size of the retinal image. We make a certain compensation for objects at considerable distances.* * Much mystery has attached to the fact that the image on the retina is upside do\\Ti, and still we see things right side up. This irrelevant wonder is like marvelling how we can see a sphere, when the cortical cells responsible for our seeing are arranged in a shapeless mass. The fact is, we have no direct personal con- sciousness of either retina or brain cells. The psychical image is a thing entirely distinct from the retinal image. To speak of the parts of this psychical image as having one position rather than another is simply equivalent to saying that a certain set of motions is necessary to pass from one part to another of the object which it represents. To pass from what we call the bottom to the top means a certain aeries of eye movements, or hand movements, and so on. l86 PSYCHOLOGY The distinctness of the perceptual image is another crite- rion. Things seen diml}^, other things equal, are judged to be far away. Objects near at hand seen dimly in this way, as during a fog, seem much magnified in size. We have dim- ness, the sign of distance, conjoined with a large image, and we consequently judge the object to be much larger than it is, because of its seeming distance. The contrary form of this confusion is experienced by persons going into the mountains for the first time. The unaccustomed atmospheric clearness renders distant objects unwontedly distinct, and so they are misjudged as much nearer and much smaller than they really are. Color also affects. such judgments. Moun- tains having a greenish hue appear nearer than those of a violet or bluish tinge. Our judgments of distance are seri- ously disturbed, also, when deprived of the assistance of familiar intermediary objects. Persons unacquainted with the sea are wholly unable to guess accurately the distance of ves- sels or other objects across the water. Light and shadow give us many trustworthy indications of contour, and even the absolute brightness of the light seems to affect our judgment, bright objects seeming to be nearer than those which are less bright. We use these various criteria of form and distance habitually and without much of any conscious recognition of the facts upon which our perceptions are based; but that the factors mentioned are really operative and essential is shown by the changes our judgments undergo the moment one of them is altered. Inaccuracies of Space Perception. — Despite its general accuracy, our visual perception is subject to sundry eccentric- ities, the precise causes of which we cannot pause to discuss. In many cases, indeed, the reasons for them are far from cer- tain, as we intimated when discussing illusion. Most of them we manage to disregard in practical affairs. The upper por- tions of vertically symmetrical figures look larger than the lower portions. The printed letter S and the figure 8 SPATIAL AND TEMPORAL RELATIONS 187 illustrate the supplementary principle, that to make the top and bottom parts appear of equal size the bottom one must be made larger. The seeming size of objects is affected by their surroundings. Figures 56 and 57 illustrate this. We might mention many other instances, but space forbids. In the establishment of effective correlations among our several sources of space perception, there can be no question, as we have previously insisted, that movement is the great factor. Objects touched are, by the movement of the eyes, at the same time seen. The superposition of one object upon another, and the successive passing of one hand after the other over the things we touch, must rapidly serve to build up Fig. 56. The middle lines of the two figures are of equal length. To most observers the lower one seems shorter. This result ia attributed to the effect of the surrounding lines. elaborate space preceptions upon the foundation of local signs, some of which are visual and some tactual. Our space, as we know it in adult consciousness, is, then, a distinctly synthetic and relational affair, developed from two or three distinct sensory sources, through the intermediation of localis- ing and exploring movements. The unity which it possesses is primarily a practical unity brought about by the motor reactions which we make upon it. Space limen. — We may add for those who are interested in the quantitative aspect of these matters, that the limen for space perception in vision has generally been given at 60", i88 PSYCHOLOGY this being the angular distance at which two lines can just be distinguished as two. Eecent experimenters report a far smaller anglC;, one observer finding the limen at 15", another at 2.5". In touch, the threshold for the detecting of two points as two is, for the finger-tips, roughly, 2 mm. The tongue is even more sensi- tive. But this can hardly be called the space limen with propriety, for single points are felt as having some ex- tension. Apart from the tongue, the finger-tips are the most delicate tactual sur- faces. Speaking generalh'', the delicacy of tactual space perception seems to be a function, first of the rich- ness of nervous innervation (those places which are most richly innervated being gen- erally most sensitive), and second, of practice, or use. Localisation of Souiid. — Although we may not admit that auditory sensations are themselves spatial, we cannot question that we localise sounds with considerable accuracy? In our view, however, this localisation occurs in the space world of vision-touch-movement. The two most important factors in the localisation of sound are, first, the relative amplitude of the sound waves distributed to the two ears, and, second, the acoustic complexity of the sound waves. If the right ear is more violently stimulated than the left, we locate the stimu- lus on the right side of the body. If the two ears are stimu- lated equally, we judge the sound to be somewhere in the median vertical plane, at right angles to the line joining Fig. 57. These figures are of equal size. To most persons the upper one appears smaller. One is perhaps misled by the disparity in length of the adjacent lines forming the top of the lower figure and the bottom of the upper one. SPATIAL AND TEMPORAL RELATIONS 189 the ears. But of the precise point in this plane we are very uncertain. With sounds that have many partial tones, these tones, especially the higher ones, are so affected by the bones of the head and by the external ear, that they reach the two ears in distinctly different condition, save when they occur in the median plane. In consequence the timbre of complex sounds differs with their direction; and it seems quite certain that we employ these differences in our auditory localisation of direction, and possibly also of distance. Our auditory esti- mates of distance, however, are highly inexact. To put it graphically, a sound on the right side may be heard as a fusion of tones a-h-c-d-e-f by the right ear, whereas by the left ear it could only be heard as a fusion of a-h-c. Now if the sound be moved to a point a little to the right of straight back, the right ear gets a-h-c-d-e, the left ear a-b-c-d. Our perception of the sound is of course always a fusion of the increment coming from the two ears. But our illustration may serve to show how these differences in timbre may act as local indices. Eecent experiments indicate that under certain circumstances at least the phase in which the sound wave impinges upon the ear may be a determining factor in localisation. Most persons seem to make their localisation of sounds either in the form of visual imagery, or in the form of quasi-reflex localising movements of head and eye. Many animals of course employ the movements of the conch of the ear to make their localisations, a method rendered impracticable for men by reason of the atrophy of the con- trolling muscles. It is possible that cutaneous sensations from the drum membrane are of some consequence in certain localisations, but the evidence for this is hardly conclusive. Functions of Space Perception. — It is not necessary to re- peat the statements made in the last chapter concerning the general functions of perception, although they all hold true here. Perception is the process by which we first become I90 PSYCHO]X)GY conscious of things, or objects. In the preceding chapter we were chiefly engaged in analysing the peculiarities of this awareness of "thingness/' or "thinghood/" as it is sometimes called, without direct reference to the spatial and temporal characteristics involved in it. But it must not be forgotten that things are encountered as parts of a spatial and temporal world, and it is through our ability to perceive space re- lations that we are enabled to adjust ourselves to the distance, form and size of objects. One has but to recall the funda- mental nature of these spatial attributes of objects in the world of common daily experience to appreciate how indis- pensable our space perceptions are to all effective conduct. One incapable of discerning the size, shape and distance of things would be practically helpless. II. TIME. Space and Time. — Although certain of our sensations may not, perhaps, contribute directly to our consciousness of space, all of them participate in furnishing us our sense of time. "We are probably never wholly oblivious to the feeling of pass- ing time, and now and then it monopolises our entire atten- tion. Unlike our perception of space, however, our direct perception of time is a very limited, cramped sort of an affair. The eye permits us to range over the vast distances of interstellar space, but our perception of time, so far as it is an immediate sensory process, never gets far beyond the present moment. It seems to be based upon our awareness of the changes occurring in consciousness itself. Primary Characteristics of Time Perception. — We may perceive the passing of time, either in the form of a mere vague duration, or as an interval, depending upon whether we give our attention to the filling of the period, or to its limit- ing stimuli. In either case what we become aware of is never a mere point of time, sharply marked off from that which has SPATIAL AND TEMPORAL RELATIONS 191 gone before and that which follows. It is always a conscious- ness of an extent of time which confronts ns, however limited this extent may be. The Specious Present. — This consciousness of the sensibly present moment is often referred to as the '^specious present" — a phrase suggested by E. E. Clay. This specious present seems to owe its extended nature to the fact that objects which have once been in consciousness do not drop out instantaneously^ but fade out often somewhat slowly. We are at any given moment, therefore, aware in the fringe of consciousness not only of that which a moment ago engaged our attention but also of that which a moment hence- is more fully to occupy us. This period of waning which our thoughts display before passing entirely out of the field of consciousness is often entitled the period of "primary mem- ory." In any case our direct perception of the passing of time is simply this process in which from moment to moment we become aware of the coming and going among our con- scious activities. Evidently the scope of such a perceptual process must be very circumscribed. As a matter of fact our direct, as distinguished from our indirect and inferred, con- sciousness of time never exceeds a few seconds. Under favourable conditions it may mount up to twelve seconds or thereabouts, but ordinarily it is much shorter. Factors in Direct Perception of Time. — Although all the senses may be employed for this purpose, hearing is the sense from which we gain our most accurate direct perception of time relations. Touch and the motor sensations rank next, and in actual practice generally operate with hearing. If we are attempting to judge accurately the length of two time intervals we tend strongly to tap, or make other rhythmi- cal movements, and our judgment is much assisted by these movements. The shortest interval which we can feel as a time period between two sounds is about 1-50 to 1-80 of a second. Sounds succeeding one another more rapidly than tg2 PSYCHOLOGY this we may distinguisli as qualitatively different from abso- lutely simultaneous sounds, but we hardly recognise them as temporally separate. Furthermore, we may feel as successive two stimuli which are objectively simultaneous. This is said to be true of the combination of a noise and a light sensation. When the auditory stimuli follow each other at the rate of less than 1-2 second, we seem to sense the sequence in one way. When they come at intervals of 1-2 second to 3 sec- onds, we have a different mode of reaction. These latter cases we feel distinctly as durations. Probably the sensory content of these durations is largely made up of kinesthetic sensations, especially from the respiratory muscles. The shorter intervals first mentioned we sense more as "mo- ments,^' although they may vary considerably in actual length. They are in no true sense, therefore, felt as mere points in time. If we compare intervals longer than three seconds we find ourselves beginning to employ our consciousness of the number of sensations, or ideas, which come into the mind. We tend to overestimate very small intervals and to under- estimate long intervals. The region of relatively correct judgment may be called the indifference zone. This is about 6-10 to 7-10 of a second. Much as in the case of space perception, we judge richly filled intervals as longer than relatively vacant intervals. "Empty time" is a myth. We always have some consciousness of change, so long as we are conscious at all. We are also subject to illu- sions and to the effect of contrast, as in spatial processes. An interval seems shorter when preceded by a long interval than when preceded by a short one, and vice versa. An interval bounded by intense stimuli seems shorter than one with more moderate limiting stimuli. If our attention is very much engaged upon some expected event we may perceive it as com- ing before another event which it actually follows. Generally speaking, our consciousness of time, as such, is proportional to our interest and absorption in the occupation SPATIAL AND TEMPORAL RELATIONS 193 of the moment. When we are bored, as in waiting for a train, or when ill, time drags outrageously. We may be con- scious of every loathsome increment in it. When, on the other hand, we are thoroughly interested, long intervals may pass as in a flash. Certain drugs, such as hashish, have a curious effect upon our time perception, lending a vastly magnified perspective to it, so that events of a moment since seem ages remote. Dreams often display a similar distortion. Indireet Time Perception. — Clearly our practical use of time relations depends largely on other processes than those of direct perception. For our consciousness of the hour, the day, and the year we resort to the sun and moon, to clocks, watches, calendars and other indirect means of information. Despite the fact that the subject does not bear immediately upon per- ception, it will be convenient to add a few words at this point upon one or two general features of our time consciousness. General Characteristics of the Apprehension of Time Relations.— When we recall intervals of time which belong to the more or less remote past, we immediately remark a seeming paradox. Intervals which actually passed very slowly for us appear retrospectively to have been very brief. Thus, a tedious illness, when time palled upon us almost beyond endurance, may in recollection seem very short, although we actually know it occupied weeks. Conversely, intervals which passed in a twinkling appear to us in memory as long drawn out. The reason for the paradox is obvious. Our feeling for the length of these remembered intervals depends upon the amount of content, the number of events, which we can read back into them. The interesting intervals are full of such things, whereas the tedious periods are characterised by a depressing sameness, which afl'ords our memory little or nothing to lay hold upon. The change which comes over our attitude towards the various intervals of time as we grow older is an interesting and familiar phenomenon. In childhood the year seems 194 PSYCHOLOGY interminable, the month majestic, the week momentous, and even the day important, to say nothing of the hour. In adult years all these periods shrink, the longest ones most mark- edly. Our attitude towards very short intervals, like the second and the minute, undergoes no change of which we can speak confidently. Our notion of very remote times, whether thought of as past or future, is gotten in an almost wholly symbolic way, like our notion of vast numbers. The difference between 2000 B. C. and 6000 B. C. is a thing for which we have a cold intellectual apprehension, quite distinct from our feeling for the difference between 1776 and 1860. Neural Basis of Time Perception. — We can say very little about the neural basis of time perception, and that little is largely of an inferential and speculative character. If the awareness of passing time rests, as we have maintained, upon our consciousness of the waxing and waning of the thought processes, there should be some fairly constant phase of the cortical activity corresponding to this conscious metabolism. We may suppose this to consist in the rising and falling of the pulses of neural activity throughout the various regions of the cortex. Time consciousness would depend, therefore, upon the overlapping of the activity of various groups of neurones. Beyond some such vague formulation as this we cannot go. Let it be remarked, however, that the conception, though vague is wholly intelligible. Physiological Time Sense. — In connection with the neural basis of time perception, we may mention two striking and perplexing peculiarities which many persons possess. One of these is the capacity for telling with great accuracy the precise hour, whether by day or by night, without any recourse to watch or clock, and without any deliberate com- putation or estimate. The other is the ability to awaken exactly at any given hour, without any preliminary disturbance of the soundness of sleep. Both of these SPATIAL AND TEMPORAL RELATIONS 195 performances probably rest upon some sort of recognition by the cortical centres of the rhythm of physiological activities constantly in progress in the body. But after all is said, the matter remains something of a mystery, a mystery which is enhanced, rather than removed, by the familiar attempt to find an explanation in "subconscious" activities. It sug- gests certain of the experiences met with in post-hypnotic suggestion. Of hypnotism itself we shall have something to say in the final chapter of this book. Functions of Time Perception. — In addition to the per- ceptual functions already mentioned, it only remains to call attention explicitly to the part played by perceptions of time. Under the conditions of ordinary life we rely very largely upon the indirect means of determining time, to which refer- ence has been made at an earlier point. This is altogther natural, because our ability to discriminate with accuracy the longer intervals of time is notoriously imperfect. Never- theless, the significance of our direct awareness of the passage of time is well brought out by the consequences of complete absorption in some occupation, as a result of which we suddenly find that we have failed to keep an important engagement. In a world in which events occur in temporal sequence a measure of constant, or at least frequent, alert- ness to the flight of time is an essential precondition to effective conduct. The constant change in progress in the events of the external world is itself a vigorous corrective of any tendency toward entire obliviousness to the movement of time, for by virtue of this change we are incessantly subjected to fresh stimulations. Although we come to rely so extensively upon artificial means for determining time, it may be questioned whether we are ever long without a direct awareness of its passage. By means of space perception we accommodate to tlie world of tri-dimensional coexistencies. By means of time perception, direct and indirect, we accom- modate to the world of sequential events. CHAPTEE VIII IMAGINATION General Account of Re-presentation. — In the preceding chapters we have seen that even in perceptual processes where the sense organs are most obviously engaged, the effects of past experience are very conspicuous. This fact will suggest at once the probable difficulty of establishing any absolute line of demarcation between processes of perception and those which, in common untechnical language, we call memory and imagination. We shall find as we go on that this difficulty is greater rather than less than our first impressions would indicate, and it will be well to come to the matter with the understanding that we are examining various stages in the development of a common process, rather than with any idea of meeting entirely separate and distinct kinds of mental activity. We called attention to this same point at the out- set of our analysis of the cognitive functions. Our study of habit brought out clearly the strong tendency of the nervous system to repeat again and again any action with which it has once successfully responded to a stimulus. The undoubted retention by the nervous organism of the modifications impressed upon it by the impact of the phy- sical world, in what we call experience, is commonly desig- nated " organic memory," and forms beyond question the phy- siological basis of conscious memory. Thus, in perception, as we have just seen, the sensory nerves may bring in excita- tions of as novel a character as you please, but the brain insists on responding to these stimulations in ways suggested by its previous experience. That is to say, it repeats in part IMAGINATION Ip7 some previous cerebral action. Similarly, we observe that from time to time thoughts flit through our minds which we have had before. This we may feel confident, from the facts we examined in chapter II, means a repetition in some measure of the cortical activities belonging to an earlier experience. Sometimes these thoughts are what we call memories, i. e., they are thoughts of events in our past lives which we recognise as definitely portraying specific experi- ences. Sometimes they are what we call creations of fancy and imagination. But even in this case we shall find it dif- ficult to convince ourselves that the materials of which such thoughts are constituted have not come to us, like those of clearly recognised memories, from the store-house of our past lives. Although we shall postpone the detailed examination of memory until the next chapter, and must therefore anticipate somewhat the full proof of our assertion, we may lay down the general principle at once, that all psychophysical activity involves a reinstatement, in part at least, of previous psycho- physical processes. Stated in terms of mental life alone, and reading the principle forward instead of backward, it would stand thus : all the conscious processes of an individual enter as factors into the determination of his subsequent conscious activities. With this general conception in mind, we have now to analyse the special form of representation known as imagination. General Befinition of Imagination. — The term imagina- tion, in its ordinary use, is apt to suggest the fanciful and the unreal, the poetic and the purely aesthetic. "VVe speak in this way of great poems as "works of imagination." We describe certain persons as of imaginative temperament when they are subject to romantic flights of fancy, etc. These implications are of course properly a part of the meaning of the word, when employed in its usual untechnical sense. But the psychologist uses the term in a broader way than this. In 198 PSYCHOLOGY the preceding chapter we discussed the consciousness of objects present to the senses. Imagination, in the psycholo- gist's meaning, might be called the consciousness of objects not present to sense. Thus, we can imagine a star which we do not see; we can imagine a melody which we do not hear, an odour which we do not actually smell, etc. Stated in the more usual way, imagination consists in the ideational revival of previous sensory excitations. Speaking broadly, both per- ception and imagination evidently involve the consciousness of objects, and their primary distinction from one another is to be found in the physiological fact that one arises immediately from a sense organ stimulation, while the other does not. The principal psychical differences we pointed out in a previous chapter. The perceptual consciousness, which is peripherally originated, is almost invariably more vivid, enduring, detailed, and distinct than the centrally initiated process of imagination, and seems to be more coercive, to be somehow more definitely " given " to us. Imagery is generally more vacillating, more fragmentary and perhaps less provocative of movement. But the similarity of the one process to the other is quite as obvious, and quite as important, as their difference. This fact is well brought out by the familiar experience in which a new and fascinating melody 'runs in the head.' All day long we are obliged to hear it mentally, and from time to time we are irresistibly impelled to sing it or whistle it. Finally it wears out and disappears. The stuff, so to speak, out of which visual imagination is made is apparently qualitatively the same kind of material as that out of which visual perception is made. Indeed, when we describe imagination as a consciousness of objects, we have already suggested that which is really the fact, i. e., that all imagination is based in one way or another upon previous perceptual activities, and consequently the psychical material IMAGINATION 199 which we meet in imagination is all of a piece with the material M^hich perception brings to us, and altogether like it, save that in imagination the fabric is often much faded and sometimes much cut up and pieced. So far as we approx- imate pure sensations in sense experience, so far do we have images reinstating approximately pure qualities as distinct from objects. Images of warmth, for instance, may have in them relatively little suggestion of objective character. Analysis of Imagination. (A) Content. — If we were to ask a dozen persons to think of a rose for a few moments, and then relate for us the ideas which had passed through their minds, we should find that some of them had at once secured a mental picture of the rose in which the colour and the form were represented with considerable accuracy and detail. These persons evidently got visual images of the rose. Others would have found that the word " rose " came at once into mind, followed by other words such as " American Beauty," " red,'^ " bud," etc. These words would, perhaps, have been Jieard mentally, and together with this mental hearing the more acute observers would report for us a similar conscious- ness of the sensations of movement which arise from the throat and lips when one is enunciating the words. This group of persons would have experienced auditory and motor imagery. Still others would report a faint consciousness of the odour of the rose, which involves olfactory imagery; and a few might tell us that they fancied they got tactual images, such as would arise from the thought of touching the soft petals. It might occur, although we should find this result rare, that some individual would report all of these images as passing through his mind in sequence. It has been asserted that we have no genuine motor, or kinsesthetic, images, because every attempt to think of a movement results in our actually making the movement in a rudimentary way; so that we get a kinaesthetie sensation instead of a kinsesthetic image. There can be no doubt that 200 PSYCHOLOGY this is often the case; e. g., the effort to think how the word " back " sounds will by most persons be found to be accom- panied by definite sensations in the tongue and throat. More- over, there can be no doubt that the normal tendency is that kinsesthetic ideational excitement should produce movement, like other forms of ideational process. Meantime, there seems to be no reason in the nature of the case why we may not have kingesthetie images in a form definitely distinguishable from the kingesthetie sensations to which they may lead; and many observers insist that their introspection verifies the reality of these images. According to the commonly accepted doctrine there are, theoretically at least, as many kinds of images as there are sense organs. If our experiment be amplified and a large number of persons be submitted to it, we shall find that it is much easier for most persons to secure with confidence accurate and reliable images of the visual, auditory, and motor varieties than it is to secure those of the gustatory, thermal, organic, and olfactory types. Tactual images seem to form a transition in difficulty of attainment from one class to the other. Later on we shall inquire into the prob- able reason for these differences. Moreover, we should find in the same way, if we gathered statistics upon the subject as others have done, that many persons, even though they can with sufficient effort command various forms of images, actually have their imagination in its ordinary use dominated by some one or two forms. From this observation has arisen the recognition of mental " types,'^ and currency has been given to the division into '''visiles," "audiles," "tactiles," "motiles," etc. These types are, as we have just pointed out, seldom or never absolutely exclusive of one another. But they indi- cate the prevalent form of mental material. With most of us there appears to be a relatively good representation of several forms, especially the visual, auditory, tactual, and IMAGINATION 20I motor. In any event we find that specific images of one kind or another always constitute the content, the material, of imagination. Image and Idea. — It may serve to clarify the terminology employed from this point on, if we pause to distinguish tenta- tively between the terms image and idea. So far as in our descriptions we have in mind the sensuous content of a thought, e. g., its visual or auditory character, we use the term image. So far as we wish to emphasise in addition to, or in distinction from, this fact of sensuous constitution the purport, significance, or meaning of the image, we use the term idea. Images and ideas do not refer to two different states of consciousness, but to one and the same state, looked at now from the side of sensory character and antecedents, now from the side of meaning. Moreover, the two aspects vary from time to time in their relative prominence. Some- times there is present to consciousness very little save the awareness of meaning. On other occasions the sensuous detail is profuse and noticeable. The matter will be dis- cussed more fully in our analysis of the concept. It should also be reiterated that in speaking of images as though they were distinct mental events, we do not mean to imply that the image constitutes the whole of consciousness at any given moment; nor that thought is made up of dis- connected bits of stuff called images. We are simply indulg- ing the kind of abstraction in which we frankly announced our purpose to indulge. Images merely represent, on the cognitive side, the more substantive moments in the onward flow of consciousness. They rise by indiscernible gradations out of antecedent conscious processes, and fade away into their successors without a vestige of abrupt separation. More- over, any given image is merged in a setting of sensory proc- esses representing the momentary bodily conditions, attitudes, etc., of which we made mention in discussing the physiologi- cal accompaniments of attention. 202 PSYCHOLOGY (B) Mode of Operation of Imagination. — If we watch the play of our images under different conditions, we observe regardless of the sense department to which they belong, cer- tain marked peculiarities which evidently call for separate classification of some kind. In dreams, for example, there often appears to be the utmost chaos in the fashion in which the images succeed one another; and when we have regard to their composition and character, they occasionally seem to be utterly novel and bizarre inventions, the like of which we have never known in waking experience. The hobgoblins of nightmares, with their inconsequential torments, are illus- trations of this sort of thing. On the other hand, in revery our minds occasionally wander o£E amid trains of images which are coherent in their relations to one another, and which evidently spring from recognisable experiences, of which they are in a measure faithful representations. Thus, the recollections of a journey may pass through our minds, diversified by excursions into connected fields of thought suggested by the various incidents of the trip. Can it be that these two forms of imagination are really identical? Is the process which brings back to mind the recollection of the sound of the multiplication table one and the same in kind with that which leads to the sudden perfection of an invention, or the inspiration of a fine verse? To answer this question in even a provisional way requires a closer exam- ination of these two forms of imagination, to which psy- chologists have assigned the names "reproductive" and " productive " respectively. Reproductive Imagination. — Eeproductive imagination consists in the representation of perceptions, or images, which have previously appeared in our consciousness. Thus, I may close my eyes and obtain a visual image of the desk at which I am writing. Such an image would illustrate what psy- chologists mean by reproductive imagery, inasmuch as my imagination would in this case simply repeat, or reinstate. IMAGINATION 203 some conscious experience wliich has previously been present in my mind. Evidently at this rate the great mass of the events which we are able to remember would be recalled by means of reproductive imagination. Our ordinary memory processes would be instances of reproductive imagination, or, as it is sometimes called, re-presentation. Productive Imagination. — Productive imagination on the other hand involves the appearance in consciousness of images which have never before entered the mind in their present order and form. Thus, the visual image of an eight- legged dog might be called up, although it is reasonably cer- tain that most of us have never seen such an animal, nor even a picture of it. Such an image would illustrate, in a rough way, what is meant by productive, or constructive, imagination. Now it is a favourite conceit of the untutored mind to suppose that it is possible mentally to create absolutely new materials for ideas, that it is possible to burst over the bounds of one's past experience and beget thoughts which are wholly novel. This is a flattering delusion which a little reflection will effectually dispel, although there is a distorted truth underlying the vanity of the belief. In the case of the eight-legged dog it is clear that, although we may never have encountered just such a creature in any of our adventures, the superfluous legs with which we have endowed him, which constitute his sole claim to novelty, are merely as legs familiar items in every experience with the canine breed. The productivity of our imagination consists, therefore, in the modest feat of putting together in a new way materials olL a thoroughly familiar kind. Although in many instances the process is less purely mechanical than in the illustration above, there is, and can be, no question of our having originated de novo fresh elements of the psychical imagery. We shall find a similar thing true of any instance we might 204 PSYCHOLOGY examine in which a genius has created a new poem, a new- statue, a new melody or symphony, a new machine, or a new commercial process. Often the result is achieved by inspiration as we say. It is not consciously thought out. This is true of the great works of art, whether in literature or the plastic arts. At other times the result may issue from persistent thought processes which we should ordinarily call reasoning. The so-called scientific use of imagination is largely of this kind. In each and every case, startling as is the result, and novel as may be the combination in its entirety, the elements which have been thus ingeniously juxtaposed are all of them drawn in one way or another from the richness of the individual's previous experience. The point mentioned earlier in the chapter must be borne in mind here, i. e., that in the use of our imagery sensuous detail often drops largely into the background, leaving us its meaning as the conspicuous thing. But in this instance there is also intimate dependence upon previous knowledge. Productive imagination is productive, therefore, only within the limits set by the possibility of combining in new ways the materials of past states of consciousness, and in discern- ing among them relations previously unnoticed. But such limitations, be it said, afford scope for an amount of orginal- ity and creative fertility which far surpass any human accomplishment thus far recorded. When we give free rein to imagination and allow it to run undirected, the process is sometimes known as fancy. When the thought is directed and made subservient to some persistent purpose, we should commonly speak of the process as thinking, reasoning or reflecting. In such mental activities there will naturally be the most complicated intermingling of imagery elements of the productive and reproductive kinds. Relation of Productive to Reproductive Imagination. — It appears at once from the foregoing statement that in one sense all productive imagination is really reproductive; IMAGINATION 205 and that in consequence we have in the last analysis only one form of relation obtaining between our present imagery and our previous consciousness. Strictly speaking this is undoubt- edly true. The differences which attract our attention to the seemingly distinct modes of imagination are primar- ily differences in the degree to which any given image, or any sequence of images, actually correspond to the entirety of some antecedent conscious event in our lives. When the cor- respondence is obvious, we think of the imagery as reproduc- tive. When it is not, we are likely to credit it with creative characteristics, and justly so, within the limits which we have designated. It only remains to notice one peculiarity about reproductive imagery which serves to modify some- what the purport of our conclusion. It is altogether problematical whether any image is ever in a thorough-going way a mere reinstatement, or repetition, of a previous perception or image. I may to-day, for example, think by means of an auditory-motor image of the word psychology ; I may do exactly the same thing to-morrow, and I shall then speak of having had the same image on two occasions. But it is clear in the first place that I cannot prove the two images to be really alike; for I can never get them side by side in my mind for comparison. When one is there, the other has gone, or has not yet arrived, as the case may be. Furthermore, if we turn to the considerations which we canvassed when we discussed the operations of the cerebral cortex, we shall find reason for thinking that no two images ever can be quite alike. For we saw that our con- sciousness, in which these images appear, and of which they are a part, apparently runs parallel with the brain activities; and it is quite certain that the brain, through its constant change of structure and tension, is never twice in precisely the same condition; and consequently is never in a position to lead twice to the same excitation of consciousness. On the whole, then, it is perhaps nearer the truth to saj 2o6 PSYCHOLOGY that all imagination is productive, rather than reproductive. When we speak of having had the same image on several occasions, what we really mean is that we have had in this way images which we employed to refer to the same object. They have thus served our purpose quite as efficiently as they could have done by being actual copies, the one of the other. The same thing is more obviously true as regards any image which purports to represent a perception. Functionally, as regards what it does for us, what it symbolises, it really does reinstate the perception; but it is not on this account neces- sarily an exact copy of the perception. The distinction between reproductive and productive im- agination must not, therefore, be conceived of as resting on ultimate differences. It marks a practical distinction, i. e., in the degree to which present thoughts resemble previous thoughts, which is useful in enabling us to indicate signifi- cant variations in the operations of our imagery. Successive Association of Images and Ideas. — This is a convenient point at which to consider the principles con- trolling the sequence of our ideas and images, as they pass through the mind. The so-called law of association, which has played historically so important a part in psychology, undertakes to formulate the facts under a single general principle, i. e., the principle of habit. We have mentioned in an earlier chapter the phenomenon known as simultaneous association. The process which we are to examine at this juncture is designated successive association. The law of association asserts that whenever two images, or ideas, have been at any time juxtaposed in the mind, there is a tendency, if the first of them recurs, for the other to come with it. Experiments seem to show that there is also a tendency for the first idea to appear if the second be present in con- sciousness. That is to say, the associative nexus works in IMAGINATION 207 a measure backwards as well as forwards. Stated more gen- erally it means that a part of any total train of thought is likely if brought to mind to reinstate the whole. Further- more^, the law asserts that so far as concerns the sequence' of ideationally aroused imagery, no image ever comes into the foreground of consciousness unless it has been in some way connected with its immediate predecessor. The order of our thoughts is, in short, determined by our antecedent experience. It is clear to the most casual reflection that this principle, if true, must operate under a number of definite limitations. "We know, for example, that a given idea comes into the mind on one day with a certain set of accompaniments, and on another occasion presents itself with a wholly different escort. Principles Controlling' Association: A. Neural Basis. — ■ How is such a variation to be accounted for? It is gen- erally agreed nowadays that the retention or preservation of associative tendencies is primarily a property of neural processes. It is a physiological thing. When the ideas are actually recalled, mental processes are also involved and the act is a psychophysical one. If we follow James in formu- lating the associative relation in brain terms, we may say that the liability of any special cortical activity, such as x, connected with the thought x", to arouse any other cortical activity, such as y, connected with the thought y^, is propor- tional to the 'permeability of the pathway joining the brain areas involved in the production of x and y, as compared with the permeability of all the other pathways leading from the brain area involved in x to other regions of the cortex. (Figure 58.) Kow this permeability must be largely a func- tion of previous use; that is to say, pathways which have by repeated employment become deep-cut in the brain tissues will, other things equal, be most pervious. Stated in purely psychological terms, this will mean that the oftener any two ideas have actually been associated with one another, the 2o8 PSYCHOLOGY more chance there will be that if the first one appears in con- sciousness, the second one will accompany it. Moreover, in so far as the principle of association depends upon the law of habit in the cortex (and this undoubtedly is its founda- tion), it must apply to all forms of psychic life, as well as to ideas and images. This is, indeed, the fact, as we shall dis- cover in our further study. But it is convenient to formulate the principle, as has been historically the accepted usage, in con- nection with ideas where its operation is particularly obvious. B. Effect of Frequency, Intensity, and Recency of Asso- ciation. — Among the many factors which must affect the permeability of the brain paths, three important ones are easily discernible. These are the frequency, intensity, and recency of associative connection.* Ideas which have been frequently asso- ciated evidently must be connected with neural ac- tivities which will tend, if once roused, to react in the regular habitual way. The ideas of Lincoln and the Civil War may serve to illus- trate such frequent con- junctions. Ideas which have been connected with one another in some vivid expe- rience will be connected with intense neural activities. Fig. 58. Although, pathways exist connecting the brain process as with the brain processes a, h, c, d, and y, if the pathway from X to y is more pervious than the others, the activity of X will be followed by the activity of y. * It will be remembered that in chapter VI we noticed a similar group of factors influencing the formation of certain illusory per- ceptions. IMAGINATION 209 whose modifications of the brain tissues will therefore tend to be relatively deep and permanent. People who have witnessed a great conflagration or a great disaster of any kind, especially if they were personally endangered, find the ideas of it welded firmly together. Often such experiences can be mentally reinstated with almost their original vivid- ness and detail. Similarly, if two images have been recently associated, the pathways joining the brain tracts responsible for their accompanying cortical activities are likely to be open; and the recurrence of the first image may readily bring with it the reinstatement of the second. The idea of the presidency of the United States will to-day most often call up the idea of Koosevelt. Our illustrations may seem to be too exclusively suggestive of associations set up originally between perceptual processes, and to take too little account of associations established primarily between ideas. But the principles involved are the same and equally valid whether they are applied to perceptual or ideational conditions. C. Influence of Context. — In actual experience associated ideas belong to more or less related trains of thought and the entire context helps to determine which of several possible ideas shall appear at a given moment. If the idea 7 times 9 pops into my head, it is promptly followed by the idea 63. If, however, 4 times 9 comes to my mind, the next idea is 36. In both cases the idea 9 is present, but the subsequent associate depends upon the special companion with which the idea 9 is united in the antecedent thought process. In a similar fashion our memory of special words in poetry depends upon the total mass of verbal associates with which they are surrounded. The word " mirth " occurs in two of the following lines, and taken alone might suggest either of the following groups of words. Taken with its predecessors it rarely fails to awaken its correct consequents. "And, if I give thee honour due, Mirth, admit me of thy crew, 2IO PSYCHOLOGY "These Mirth delights if thou canst give, , with thee I mean to live." In cases of this kind the association is often between motor reactions of enunciation, rather than between the images of the words. We simply find ourselves making the proper enunciatory movements and that is the end of it. Eelated to the general influence of context is a distinc- tion which Miss Calkins has pointed out. In certain associative sequences the image which comes into the mind entirely displaces the one which previously held sway. She calls this type of case desistent association. Our illustrations have been chiefly of this type. In other cases, however, a part only of the departing image is lost, the rest being taken up into the new image which succeeds it. This she calls persistent association. For example, in revery the image of a face may come before the mind. Without undergoing other change, it may presently be seen as dark instead of fair. This analysis seems to touch upon a real distinction and the last illustration suggests the case of association by similarity of which mention will be made presently. But the distinction clearly introduces no basal alteration into the general nature of the principle controlling the ideational sequences. D. Interest and Emotional Conditions. — It remains to remark one further factor of probably greater importance than those already mentioned in its effect in determining what associates shall. recur with an idea at any given time. The factors mentioned hitherto bear principally upon the conditions controlling the original fixation of the association. The present factor refers in part to this, but more imme- diately to the circumstances attending the revival, the recall, of the train of thought. This is our momentary interest, the prevailing tendency of our attention. If our minds are dominantly engaged upon any line of thought, as when we are wrapt up in some absorbing problem, or plunged in IMAGINATION 211 some profound emotion, the ideas which flood our minds are almost wholly such as sustain intimate relations to the mat- ter in hand. When we are overcome by sorrow all our thoughts centre about our grief. Ko other thoughts can gain a hearing from us. And the same thing is true in varying degree of any intense mental preoccupation. The continuity of our interest is therefore an influence of abso- lutely prime importance, accounting readily for the omission, as well as for the inclusion, of those ideas which we find in point of fact have actually been omitted from, or conjoined in, associative combinations. We see, then, that the principle of association, or cortical habit, is modified, not only by the changing relations among the factors of past experience already mentioned, e. g., such as frequency and recency, but also by the present psychophysical conditions reflected in such things as our attention and interest. This means, so far as concerns the brain, that those pathways are normally most pervious which connect most intimately with the entire mass of ongoing brain processes. The astonishing vagaries of dream consciousness illustrate what may occur when all dominating purpose is removed and the associative machinery is allowed to run wild and uncontrolled. E. Contiguity, Similarity, Contrast, Cause and Effect, — Psychologists have been interested in various types of asso- ciation, which they have called association by contiguity, association by similarity, contrast, cause and effect, and the like. They are all reducible to the forms previously men- tioned, but their prominence historically renders it expedient to dwell on them briefly. Association by contiguity is essentially identical with cer- tain of the processes of which we have been speaking here- tofore. A suggests B, not because of any internal connection, but because the two have often been contiguous to one another. This contiguity is originally perceptual in char- acter. The objects are actually present together to the 212 PSYCHOLOGY physical senses. Events related to one another as cause and effect are commonly experienced in this way. All association is primarily dependent upon the contiguity of perceptual objects, as will be readily apprehended when the dependency of images upon perceptions is recalled. It must not be for- gotten that objects perceived together ordinarily share in whatever interest may at the moment be dominant. Conse- quently it is probably rare that contiguity as a determinant of association operates independently of interest. Ideas apparently follow one another at times, however, which could not have been previously experienced together, and in certain of these cases we remark at once that the two things suggested by the ideas are similar, contain an internal element of connection. "We meet a total stranger, perhaps, and instantly observe the similarity to some absent friend. Poetry owes much of its witchery and charm to the delicate and unusual resemblances which the poet detects for us, as when he says: "So gladly, from the songs of modern speech Men turn, ..... And through the music of the languid hours. They hear, like ocean on a Western beach The surge and thunder of the Odyssey." All the more conspicuous forms of genius seem highly endowed with this type of association, which is undoubtedly a genuine form of mental activity. We shall err only if we suppose the consciousness of similarity to be the invariable antecedent of the association. As a matter of fact we often observe the similarity after the association has occurred, not before, as should be the case if it were strictly speaking a cause. But this is not always the case. For example, we frequently see strangers upon the street who look familiar to us, yet it may require several moments of reflection before we can recall the persons of whom they remind us. A number of psychologists have suggested that the brain activities IMAGINATION 213 involved in thoughts of two similar things are in part identical, and that consequently we have in their suggestion of one another a further instance of the principle of cortical habit. (Figure 59.) The brain processes x and y, having the simi- lar thoughts x^ and y^ as their concomitants, possess a common brain activity z. When x is active, there is thus a chance that the excitation of z may stir up y, to which z also belongs. Oftentimes the elements of likeness between two objects are several, as in cases of personal resemblance. On other occa- sions the resemblance may reduce to a single element. But the principle of explanation is the same in either case. Fig. 59. Association by contrast is really a modification of the con- tiguity and similarity classes. Things are not felt as con- trasting unless they have some element of likeness, and to feel this likeness and difference commonly involves experienc- ing them together, as when we come to remark the contrast of black with white. Even if no factors were operative in association, other than those we have already mentioned, we should find it practically impossible ever to predict with confidence what particular idea would come into the mind at any special moment. The law of association is not, therefore, a principle of 'prediction, but simply a formula for rendering intelligible 214 PSYCHOLOGY in a schematic way the nature of the influences which con- trol the order of our thoughts. Neural Basis of Imagery. — Two divergent views are held as to the neural basis of imagery. We have already referred to these. The one maintains that imagery depends upon the activity of the same cortical regions that are involved in per- ception. The neural distinction between them is supposed to rest chiefly on differences in the intensity of the nervous excitation, coupled with a varying amount of difference in the extent to which the association areas are involved. The other view holds that the cortical regions involved are prob- ably different in some important particulars, the areas con- cerned in the imagery processes of each of the senses lying perhaps along the borders of the regions devoted to the re- ception of the corresponding sense stimulations. This latter view is based largely on the implication of certain clinical cases already cited of persons who could perceive correctly without being able to call into mind images. This evidence the defenders of the view reinforce by other more ambiguous clinical facts and by their introspective conviction of a difference in the mental quality of the two states. The ques- tion must be regarded as still open, although the author feels that other interpretations of the clinical cases are pos- sible than those adduced by the supporters of the second view. In any case it seems certain that the recognised sensory areas are involved to some extent in all ordinary processes of imagination, and the regions of the brain concerned can be identified by consulting chapter II. Genesis and Function of Imagery. — The best clue to a correct understanding of the function of the image is to be gained, as in the case of all organic activities, when possible, by examining the conditions of its genesis, its appearance upon the field of psychophysical processes. In several of the preceding chapters we have examined the evidence underlying our thesis, that consciousness appears IMAGINATION 215 at those points where the purely physiological mechanisms of the organism prove inadequate to cope with the requirements of its life. We have seen how the organism is endowed at birth with certain established sensory-motor neural pathways, by means of which it is enabled to respond with appropriate movements to certain primitive kinds of stimuli. We have also seen how, at the places where these responses are found insufficient, sensory consciousness appears; and we find, first, vague sensation processes, and then crude perception. In our study of attention, we noticed how the mind, working upon this crude perceptual matrix, succeeds in differentiating it into the multitude of qualities and objects which con- stitute the world of the adult. In seeking to detect the appearance and the function of imagery, we must remember, then, that from the outset of life organic activities are in progress and the sensory-motor activities in particular are in full swing. Each sensory stimulus is producing move- ments, which in turn are productive of fresh sensations. It is out from such a cycle of onward moving coordinations as these, therefore, that the image emerges ; and if our previ- ous hypothesis is really adequate to all the facts, it must be that the image is called forth by some need of the organism which the processes that we have already described are incom- petent to satisfy. This is undoubtedly the case, and we have only to observe the evident limitations in the capacities of the perceptual processes, taken by themselves, to discern cer- tain of the functions which our images subserve. Perception enables its possessor to register in consciousness the particular object momentarily presented to the senses. But if consciousness never advanced beyond the merely per- ceptual stage, it is apparent that we could never develop any highly systematised and intelligent movements of response to environmental demands and opportunities. Intelligent deliberation would be impossible. We should always live in the immediate present, and our minds could consciously look 2i6 PSYCHOLOGY neither backward nor forward. Now it is in the image, with its ability to carry such prosjoective and retrospective mean- ings that we find the psychical mechanism for accomplishing both these highly important functions. If an organism is to be in the fullest possible measure master of its own fate, it must be able to bring to bear upon the incitations of any particular stimulus all the informa- tion which its total experience will permit. Its response must thus represent not only the intrinsic tendency to overt action, which belongs to the stimulus itself, but it must also represent and express all the tendencies to movement which remain as the result of yielding to previous incitations. Unless there be some organic arrangement of this kind, by means of which each act may represent with some adequacy the product of all related experiences in the past, one's actions can hardly rise above the level of haphazard reflexes. It is obvious that mere perception — although, as we have noticed, it does embody in a certain way the outcome of antecedent consciousness — does not in any sufficient manner provide for such a focussing of one's past experiences upon the selection of specific acts, as is demanded by the best accommodatory responses. Without the image we might make many appro- priate reactions, but we should also make many more in- appropriate ones than we now do ; and any high development of intelligence would be impossible.* The image is, then, the primary psychical process by means of which we bring into mind at need the experiences of the past. It is also the means by which we forecast the future. If I wish to remember what I read yesterday, I accomplish it by summoning images which represent the experiences at issue. If I wish to decide which of several lines of conduct I had best pursue, or which of several possible acts my enemy *The limitations of animal intelligence are largely to be accounted for by the lack of well-developed processes of the image- idea type. IMAGINATION 217 is likely to hit upon, I do it in either case by the use of images, which serve me in my tentative prognostication. These images may of course be of any variety, but in my own case they are likely to be largely visual — images of objects, or scenes — and auditory-motor images of words, for my own thinking goes on largely in these terms. Moreover, they may be extremely vague and their sensuous detail be almost swamped in the meaning which they convey. But, whatever its form, it is the image which thus affords us the method whereby we shake off the shackles of the world of objects immediately jDresent to sense, and secure the freedom to overstep the limits of space and time as our fancy, or our necessity, may dictate. Of certain of the important uses to which man has put his imagination — in the large sense of the term — in science and art, myth and religion, we shall refer in a later chapter. Here we are preoccupied with the more rudimentary aspects of the process. If we have correctly diagnosed the chief function of our imagery we may be certain that it makes its first appearance at a very early stage in the conscious life of the human being. For obvious reasons it is not possible to designate the precise moment in the unfolding of the life of the mind at which the image is clearly and distinctly differentiated from the vague matrix of sensory-motor activities which we have seen characterising the first experiences of the child. But we may be confident that it is beginning to emerge in some sense departments, whenever we see unmistakable signs of volition, say at about the twelfth week in most children; and there is no reason why it may not be present, in a crude, indefinite way, from the beginning of extra-uterine life. The Connection of Imagery with the Exercise of the Senses. — The development of imagery runs parallel in a measure with that of perception, with which, as we saw in the previous chapter, it is very intimately connected. It 2l8 PSYCHOLOGY holds to reason, without any elaborate Justification, that if any sense organ is allowed to go unused, or is used infre- quently, the imagery belonging to that special sense cannot develop freely. In confirmation of this general assertion we have but to notice that the imagery which most of us find we can command with greatest accuracy and flexibility is that belonging to the perceptual processes with which we are most intimately familiar, i. e., vision, hearing, movement, and touch. Compared with these, our images of temperature, smell, and taste are relatively impoverished. Moreover, chil- dren who lose their sight before they are five years old com- mor^ly lose all their visual images, thus exhibiting further evidence of the connection of the image with sense organ activity. Nevertheless, we have to admit that we display individual peculiarities and preferences in the kind of imagery which we employ that cannot be satisfactorily ex- plained in terms of sense organ activities. The eye and the ear may be used with indifl^erent frequency and seeming effectiveness, and still the imagery be dominantly of either the visual or auditory kind. Differences of this sort probably rest upon unassignable organic variations in the cerebral cortex. The Training of Imagery. — If we examine the type of development which characterises the growth of any special form of imagery, such, for example, as the visual, we shall find that two distinct tendencies are discernible. We find (1) that the number of objects which can be simultaneously visualised increases, and (3) that the vividness, detail, and definiteness of the image increases. It is astonishing to observe how rapidly this capacity for visualising unfolds in response to a little systematic effort and practice. By devot- ing to the task a few minutes each day for a week, one may learn to visualise with great detail and remarkable accuracy the form, size, colour, etc., of even large and complex objects, such, for example, as great buildings. Frequently at the IMAGINATION 219 outset we find tliat our images are relatively faint^ meagre, and unstable; they lack vividness and veracity in colour, detail in form, and appropriate dimensions in size. Images of other varieties, auditory, for instance, are similarly defective at times, and yield as a rule to discipline, with a corresponding form of development. But after all, the important development of our imagery is not to be found by inquiring for such changes as we thus detect, when we consider it of and by itself apart from its place in the totality of psychophysical activity. The essen- tial thing is the increase in the dexterity with which we employ it, and the growth in the efficiency with which it serves its special purpose in the economy of the organism. We have already commented upon its principal function. It is the psychical device by which we are enabled consciously to focalise upon our acts the lessons of our previous relevant experiences, and through which we forecast the future in the light of the past. To perform this function with the greatest ease, prompt- ness, and efficiency is the goal toward which the develop- ment of our imagery tends, both in those cases where we, as psychologists, purposely bend our efforts in that direc- tion, and also in those cases characterising ordinary prac- tical life, in which our attention is concentrated upon, and absorbed in, the execution of some act, and for the moment is oblivious to the means employed. We have already, in an earlier chapter, outlined the general nature of this development, and we need hardly do more here than refer to the significant facts, and cite an instance or two of the process involved. If I wish to express some proposi- tion with the greatest possible force and clearness, I go about it by calling into my mind auditory-motor word images. Clearly I might use other kinds of imagery without affect- ing the relations which we are now examining. As a matter of fact I generally use, as do most persons under these 220 PSYCHOLOGY conditions, auditory and kingpsthetic imagery. From among these word images I select that combination which appeals to my judgment as most appropriate and effective. Evidently the success which I achieve will be in part conditioned by the extent and richness of the images which I am actually able to summon. We speak sometimes of persons possessing a rich vocabulary. In the case of our illustration;, my posses- sion of a good vocabulary means, when stated in strictly psy- chological terms, that I can command a large and effective group of auditory-motor word images. As a child my imagery of the verbal kind is necessarily circumscribed in amount and phlegmatic in operation. When adult years are reached the amount of the available imagery is ordinarily much augmented, but unless there be discipline in its actual use^ it is commonly found that much investment of time and effort is needed in order to secure the best and most expressive terms. The only real and infallible means of training one's imagery for such actual operations is found in the definite use of it, either by writing or speaking. Prac- tice is here, as elsewhere, the one invariable clue to the highest attainable success. The business of such imagery is always to be found in some act, and the only way to develop it and make it reliable and efficient is by worTcing it. For various reasons, which we need not pause to discuss (perhaps largely due to emotional conditions), the possession of a good vocabu- lary for writing purposes does not necessarily carry with it a rich vocabulary for speaking; and in less degree the con- verse is true. One commonly requires separate training for each form of activity, if the best results are to be attained. Imagery and Motor Habit. — When we were discussing the principle of habit we observed that all such coordina- tions as those which we have Just mentioned tend, under the influence of practice, to become essentially automatic; and that consciousness consequently tends to disappear from their control. If this be always the case the idea is at once IMAGINATION 221 suggested that in such a process as is involved in our illustra- tion, i. e., the process of linguistic expression, the same tend- ency should be in evidence. I believe this to be actually the fact, and I think a little observation will confirm the position. We shall have occasion to examine the question more at length when we discuss later on the relation of language to reason- i ing, but a word or two may properly be inserted here. Just in the degree to which our linguistic expression involves thoroughly familiar ideas, and deals with familiar situations, do we find our consciousness of definite imagery vague and indistinct. A student inquires : " What did you mention as the date of the battle of Waterloo?" Instantly, almost without any definite consciousness of what I am about to say, I find I have replied—" 1815.'^ But when the expres- sion is of some relatively unfamiliar idea, when the thought presents the possibility of several discrepant modes of utter- ance, I promjstly become aware of imagery. Not always verbal imagery of course. That consideration is wholly secondary. But imagery of one kind or another I always find when the coordination required cannot be executed in the purely — or almost purely — habitual manner. If the situations vsdth which we have to cope by means of speech were more widely fixed, instead of being, as they are in fact, relatively unstable and fluid, relatively changeable, I see no reason to doubt that speech, like walking, might become essentially automatic — as I believe it to be in part already. Summarising, then, we may say that all imagery arises out of perceptual activities, upon which its appearance is, therefore, most immediately dependent; it develops by use in the actual processes of controlling action, and develops its real functions in no other way. This accounts for its appear- ance in greatest profusion in connection with those sense processes which are most significant for human life. It tends to drop away after it has served, in the general congeries of consciousness, to establish effective habits. CHAPTEE IX MEMOEY Memory and Imagination. — A considerable portion of the mental events which we examined in the last chapter as instances of imagination, might with propriety have been described as phases of memory. In our common use of the term " memory/' we mean to indicate such processes as involve recollection in any fashion whatever. We say in this way that our memory informs us that Napoleon was impris- oned at St. Helena; that 8X'?=56; that yesterday was rainy, etc. We also speak of remembering that on a certain occasion we made a certain remark to a certain individual. Evidently these illustrations might all be described as cases of reproduc- tive imagination, for they all involve reproductive imagery. We may be reasonabty sure at once, then, that conscious memory and imagination have one point at least in common, i. e., the image. But there is one important difference between memory, in the more precise meaning of the word, and mere imagination, which makes it desirable to devote a separate chapter to its study. We might go on indefinitely having similar, or even identical, images pass through our minds, and, if we did not recognise them as having been previously portions of our experience, we should never in any strict sense be able to speak of our having a memory process. In memory, our con- sciousness not only re-presents old experiences to us, but we are aware of the ideas thus brought to us as actually standing for items of our previous states of consciousness. If I am turning over in my mind the wisdom of making a MEMORY 223 journey to India, the thoughts which come into my mind are brought there by some form of reinstatement of knowledge which I have gained on some earlier occasion. Productive, or reproductive, processes of ideation are at work. But my attention may be wholly monopolised with the reference of these thoughts to the future. They may not at any point in. my thinking present themselves as mere exponents of my antecedent experiences. I think of India as an interesting country, and my attitude is of course determined by things which I have previously learned about it. But this fact of my having gotten my information in some moment of my earlier life may drop wholly out of sight in my enthusiasm over the knowledge itself. Clearly, then, there is a distinc- tion between the mere reappearance of ideas in consciousness, and the fact of memory, as involving recognition of these ideas as elements in my oivn past history. All conscious memory is reproductive imagination, but not all reproductive imagination is memory. Definition of Memory. — We may define memory, then, with more preciseness than we have before attempted, by quoting James' words. " Memory proper — is the Jcnowledge of an event or fact, of which meantime we have not been thinking with the additional consciousness that we have thought, or experienced it before/' Method of Recall. — Let us take a specific instance of memory as thus defined and examine it. Suppose we attempt to recall where we were and what we were doing at 10 o'clock on the fifteenth day of last month. Ordinarily we shall be obliged to begin by remembering upon what day of the week that month began, and this in turn may require our remembering upon what day the present month came in. Let us suppose that we find in this way that the fifteenth of the preceding month fell upon a Tuesday. If our life is subject to a fixed routine, this will generally suffice to give us the clue to our whereabouts and doings at the hour suggested. After 224 PSYCHOLOGY a moment's reflection we remember, perhaps, that we were in the library reading American history, and upon a little more reflection we may recall what other persons- were in the room, and what portions of the text we were reading. Memory and Association, or Cerebral Habit. — This analy- sis at once reveals what we shall find true in any case we may select, i. e., that we call back our memory ideas, or images, by means of ideas which are associated with them. In order to solve the problem set us by the question in our illustration, we began by calling into mind ideas which we knew to be con- nected with the solution. In this way, little by little, we obtain the clue to our occupation at the time suggested. Memory depends, then, for its operation upon the principle of association, and this principle is in the last analysis identical with the law of habit in the cortical processes of the cere- brum, as was explained in the previous chapter. This phy- siological aspect of the matter is particularly well shown in cases where the recall takes place in the form of motor acts rather than in definite ideas. If I am asked for the street address of a friend, the reply may come instantly in the from of spolcen words and often quite without any pre- liminary ideational process. The preservation by the nervous system of acquired tendencies to action is called "^organic memory," as has already been stated. Memory and Imagery. — If we inquire into the nature of the mental content disclosed in our conscious memory, we find that it is made up of images — visual, auditory, motor, etc. When we reach the goal of our endeavour, and succeed in recalling our presence in the library, we discover that the content of our thought is not only made up of images, but that over and above this fact is to be remarked the peculiar character of the imagery. Just in the measure in which our recollection is detailed and confident, we shall ordinarily find the imagery profuse and exact in its representation of the temporal and spatial order of the events and objects present MEMORY 225 to consciousness in the original experience. However, some persons execute almost all their thinking, including the process of recall, with a highly schematic sort of imagery which lacks detail and is extremely fleeting and unstable. The meaning of their conscious states is for them the per- sistently dominant thing and to the other aspects of their experience they reinain consistently oblivious. Memory and Eecognition. — One still more important peculiarity is noticeable in this case of memory which we are analysing. After we have, by means of associated ideas, gotten into mind our whereabouts and acts at the time named, and after the imagery portraying our situation has been developed in consciousness, it is still necessary, if this is not all to be futile, that we should recognise, identify, and assent to the meaning of the ideas thus brought before our notice, .as indicating the actual experience to be recalled. This fact of recognition we have previously emphasised as a dis- tinguishing mark of memory when compared with imagina- tion. It seems to be an ultimate and unanalysable property of consciousness. But however much it may baffle our attempts to dissect it, there can be no question of its funda- mental import, and we must accordingly take account of it. Memory an Outgrowth of Recognition. — It seems on the whole probable that memory, in the meaning of our defini- tion, has grown out of a cruder process of recognition which, although it is now no longer sole proprietor of the activity, still accompanies the memory act in its elaborate forms as a basal and indispensable cliaracteristic. If we examine, for example, the actions of an infant, we very early observe evi- dence of the recognition of objects. Thus, the mother's face, the sounds of preparing food, the contact sensations occasioned when clothing is put on or off, are all of them recognised at a period when it would be hazardous to assume that any independent memory imagery has as yet become dis- engaged from the general sensory continuum of consciousness. 226 PSYCHOLOGY Clearly then, the recognition process may begin with conscious events which are dominantly of the sensory and perceptual kind; whereas our contact with it thus far in our study has been primarily in connection with representational activities of the centrally initiated character. Conditions of Sensory Eecognition. — When we con- sider the neural conditions under which sensory recognition arises in the young babe, it is immediately suggested to us that recognition depends primarily upon the reexcita- tion of pathways in the nervous system over which nervous impulses have previously travelled. The organic reaction which such stimulation sets up finds an echo in consciousness, which is probably the beginning of recognition. If we take this fact of recognition, in connection with the other facts we noticed when describing the beginnings of habit, we shall secure a deeper insight into the mode of development peculiar, to the process here at issue. It may be said at once that recognition plays (implicitly or explicitly) a fundamentally important part in every one of the cognitive operations, from perception through memory up to reasoning. Take the case of a child learning to recognise its mother. At first, when the mother takes the child up to be fed, the visual, tactual, and gustatory stimulations set up miscellane- ous movements which are in the main uncoordinated and utterly variable. Little by little, however, as these sense impressions are repeated, and their agreeable consequences are experienced, the movements tend, after the manner we have already described, to settle down into the relatively coordinated groups which the experience encourages. Smil- ing, gurgling, jerking the limbs in movements anticipa- tory of being taken up, rapidly appear and become fixed as habits. Very quickly, then, these repeated sense impressions set up sensory-motor coordinations, of which the conscious process of recognition is the psychical accompaniment. These impres- MEMORY 227 sions promptly come to mean certain movements. Indeed, the movements are actually initiated by the impressions, and recognition is the mental state which observes, assents to, and in a sense guides, these physiological responses. As the re- sponses become more and more automatic, the psychical part of the activity tends to evaporate, as we have so often pointed out. In just the measure in which this occurs do we cease to have any clear, definite, vital sense of familiarity, any tingling thrill of recognition. This is illustrated in adult life by the " matter of course " manner in which we respond to the thousand and one objects which we see every day — the books, papers, ink-stand and pens on our desks, the tables, chairs, windows and lamps in our rooms, the trees on our familiar streets, the shape and colour of our own houses, etc. We do the appropriate things in the presence of these objects and such overt acts on our part constitute in cases of this kind Bubstantially the sole expressions of recognition. Practically we recognise all these things of course, but it is with a rela- tively automatic, dim kind of consciousness, which contrasts sharply with the vivacity and distinctness of the feeling which we get upon first seeing these same objects after pro- longed absence. As development proceeds, the overt move- ments themselves often become superfluous and are largely inhibited, or at least they tend to become nascent; they are resolved into mere transitory attitudes. We may feel moderately confident, therefore, that recogni- tion of the sensory variety rests upon the reinstatement of acquired sensory-motor coordinations; i. e., on the genetic side it displays a period of conflict of impulses and move- ments with maladjustment, a period of increasingly efficient adaptation, and a final period in which the conscious factor tends to drop out, sometimes apparently doing this, sometimes stopping just short of disappearance. Conditions of Ideational Recognition. — When we rec- ognise ideas, or images, in distinction from perceptions, as 228 PSYCHOLOGY having previously occupied our consciousness, the strictly mental features of the case do not differ materially from those we have just described. We are ordinarily, perhaps, more definitely aware of the fringe of suggested images with which an idea that we recognise promptly surrounds itself, although this is apparently by no means an invariable feature of recognition. But the production of an emotional reaction, or mood, which we may name the familiarity feeling, is com- mon to both the sensory and the ideational forms of rec- ognition. Generally, but not always, the act of recognition is agreeable, and this, too, is true whether the act be of the sensory or the ideational kind. Probably the mere act of recognition is, as such, always agreeable, although the object, or content of the thought recognised, is of course sometimes quite otherwise. Moreover, both kinds of recognition, sensory and ideational, may vary almost indefinitely as regards the distinctness and the degree of elaboration belonging to the various parts of the process. We may thus find that an idea which comes into our mind — for example, the visual image of some person's face — calls up the vague feeling " familiar," " seen before," and nothing more. Or it may surround itself with a number of other images and we may at once recognise it as the face of a speaker whom we heard last week. In such cases words are very likely to be called up, whether in the form of definite auditory images, or in the form mentioned in an earlier paragraph, as actual articula- tions. The person's name may be thus pronounced either aloud or under the breath. Here as in the case of sensory recognition, overt acts are frequently the conspicuous expres- sions of recognition. In all instances of conscious recognition, however, it must be remembered that the mental act of explicit recognition is something unique; something which is not simply synon}^- mous with the accompanying conditions which we have been describing. When v/e get these accompanying conditions we MEMORY 229 get the act too, and when they are all absent, the act is apparently absent. But the mental relating of the present idea, or perception, to the past as familiar is something dis- tinctly additional to and beyond these concomitants. On the physiological side it seems probable that ideational recognition is much like sensory recognition, save as regards the neural processes which initiate it. The sense organ activ- ity is clearly not the immediate predecessor of the cortical action underlying recognition in the case of its ideational form. But the motor response is essentially identical, and its cortical basis may be, for all we can see, of a similar character. The matter can be put diagrammatically, as in the accompanying iigure (60). In the case of sensory recogni- FiG. 60. tion the process starts in the sense organ (SO) and is trans- mitted to the sensory regions of the cortex (SC), arousing perception. Thence it is transmitted, either directly to the motor centre (MC) and thus perhaps initiates movements of the recognitive sort, or it is transferred to other cortical centres (Cj, C^, etc.), resulting in the arousal of supple- mentary ideas, which serve to give the perception its place in past experience, and the process is then carried over to the motor regions (MC), and thus out into the voluntary and involuntary muscles, producing the habitual response in com- pletion of the sensory-motor cycle. In ideational recognition 230 PSYCHOLOGY the process is of the same character, save that now the sense organ origin of the cortical excitation is lacking. The proc- ess starts, so far as we can discern, in some cortical centre like Cj. At all events, if a sensory process is really respon- sible for the result, it lies so far back in the series of cortical activities that we cannot confidently connect it with the result. It ought not to be necessary to point out again that the actual motor reactions characterising these processes of recognition may be of an extremely rudimentary and frag- mentary kind. But the tendency to make the movements, with its indication of a degree of innervation in the motor cortex, seems to be a genuine part of the act. Remembering and Forgetting. — It has already been abun- dantly emphasised that memory (using the term from this point on to the end of the chapter in the broader sense of common parlance, as equivalent to recollection in its various forms) depends in the last analysis upon the retentiveness of the nervous tissues. When we are not occupied with a thought, or an image, so far as we know, the thought, or image, simply goes out, ceases to exist. Certain psycholo- gists prefer to think of these psychological facts as stored up in the mind in the form of what they call " psychical disposi- tions,^^ or tendencies. But however it may fare with this last mentioned theory, the modifications of the cortical tissues which our experiences bring about are certainly relatively durable; and when the cortex is called upon to resuscitate a previous experience, it summons the appropriate centres, with their imbedded modifications, to perform again the action previously executed. This is apparently the physical basis of imagination and memory. In one sense, therefore, it is probable that no item of our lives is ever literally and entirely forgotten. Even if we find it impossible, as we sometimes do, voluntarily to recall a certain idea, we must believe that the experience in which we originally encountered it has left its indelible impress upon the substance of the brain, MEMORY 231 whose action will in consequence be somewhat different from that which it might have manifested had the experience in question never befallen us. Despite this belief, forgetfulness is a constant and often exasperating characteristic of daily life. It also has a useful function, which we do not always recognise. From the psy- chophysical point of view we obtained the most important explanation of the value of forgetting when we were examin- ing the facts about attention. In the chapter devoted to attention we found that consciousness is seemingly never impartial in its response to the objects presented to it. It is always primarily concerned with some particular portion of the objective field. It neglects this and attends to that, it is dimly aware of this and keenly cognisant of that. Now, if memory is dependent upon the modifications which neural stimulations impress upon the cerebral cortex, and if con- sciousness and cortical action run parallel with one another, as we have seen is apparently the case, it holds to reason that those items in any experience which procure our undivided and concentrated attention must succeed in leaving deeper and more permanent traces in the cortical tissues than do those to which we attend in the margin of consciousness, or than those over which we pass uninterestedly. Although the undoubted tendency of the brain is to register and store up all the impressions which are imposed upon it, the gradual change of organic structures must inevitably bring it about that some of the less deeply engraved modifications should gradually become so faint and so disused as to render them practically inert and incompetent to participate vitally in the operations of memory. Temporary functional disconnections of brain centres that normally are connected are familiar to all of us. I know my friend's middle name perfectly well, and yet when asked for it a moment ago, I could not command it. Some momentary stoppage of the associated pathways in the cortex checked the attempt at recall. Many of the most 232 PSYCHOLOGY serious disorders of insanity involve this kind of disconnection and disintegration among ideas, of course much exaggerated. One primary reason for our forgetfulness, therefore, is found in the process of attention. We must expect to forget a goodly part of all those items of experience to which we do not lend a vigorous and forceful attention. The only compensation for the lack of such concentration is found in the tedious process of repetition, by means of which we may, with even indifferent attention, grind gradually into our brain tissues any material which we desire to retain. Forgetting has its use, however, in freeing us from the incubus of much utterly valueless experience. On the whole we remember fairly well those things which are of practical importance to us. Were our minds so organised as to retain with impartial accuracy all the events in our experience, and were their total capacity to remain unchanged, we should find our intellectual possibilities immensely curtailed by the obtrusion of the insignificant and irrelevant. While we are occasionally incommoded by forgetting, it is undoubtedly on the whole an added source of efficiency in our mental opera- tions, that we find the unimportant elements of our knowl- edge so frequently dropping out of our memories. Defects and Abnormalities in Recollection: A. Familial Phenomena. — We obtain an interesting side-light upon nor- mal memory processes by observing some of the common defects and abnormalities to which it is subject. These are in the main exaggerations of common and familiar deficien- cies. Thus, in one form of hiental disorder everything is forgotten the moment it passes out of the range of percep- tion. We observe in ourselves the counterpart of this case, when after reading a sentence, for instance, we find, as occasionally occurs to all of us, that for a few moments we are absolutely unable to remember anything about it, and often must ignominiously read it again. The opposite type of abnormality is met with in the form of vastly heightened MEMORY 233 sensitivity to impressions, which can then be recalled with marvellous accuracy and detail. The mathematical prodigies who can recall lists of a hundred or more figures after a single glance are cases in point. Idiots sometimes possess astonish- ing verbatim memories of the same kind. With most of us the only phenomenon closely corresponding to this is found in our ability to recall experiences which have been char- acterised by intense emotional disturbance. The details of some episode in which we have been greatly terrified may linger in our memories with a vividness which rivals the dis- tinctness of the original experience. Again, the memory of events during a grave illness may be almost wholly lost. A similar obliviscence as to the occurrences preceding a severe accident is very frequent. There are numerous abnormalities in which the order of remembered events and the time of their occurrence is distorted ; things are persistently " remembered/' which never occurred, and imaginary events are interpolated among real events, in a manner which bafiles analysis. The counter- parts of these last named defects in our own every-day life and in the case of children will suggest themselves at once. A simple experiment can be readily performed to illus- trate these errors. If a series of numbers containing seven or eight digits be read aloud to a group of people and they be asked to write down at the completion of the reading of each series the numbers as they remember them, it will be found that three characteristic forms of error are made. (1) Digits will be given in an order different from that in which they were read. (2) Certain digits will be left out entirely. (3) Digits which were not read at all will be inserted in place of some which were given. B. Diseases of Memory. — An interesting disease of memory which furnishes striking confirmation of our con- elusions concerning the dependence of memory and imagina- tion upon the image, consists in the loss of memory for specific 234 PSYCHOLOGY forms of sensory material. Thus, the visual memory may be entirely lost, so that one cannot recall how objects look. Or the auditory images of words may be obliterated. If the im- agery which is lost be of the variety chiefly employed by the patient in his thinking, the result is inevitably most disastrous, reducing the victim to a condition bordering upon imbecility. General amnesia (loss of memory), which may arise from some severe shock, or may be found in dementia, as in the case of the very aged, involves a total loss of memory of all kinds, for events of the preceding moment as well as for remoter events. Partial amnesias are found which may either involve a limited portion of time, as when a person is unable to remember anything that occurred on the occasion of a severe accident, or it may involve some special sensory process, as in the cases mentioned in the preceding paragraph; or it may involve certain subjects only as in cases of forgetting a foreign language. In somnambulistic states events can be recalled which occurred in previous somnambulisms, but which in the interim have been entirely forgotten. A similar condition is sometimes met with in hypnotic sleep. The profound disturbances of personality met with in certain cases of hysteria are related by Janet to fundamental cleavages in the memory processes, by virtue of which one set of experiences gets entirely severed from the rest of experience and serves as the focus for the establishment of a new personality. We shall refer to these cases of multiple personality later in the book. Meantime facts such as we have just rehearsed show clearly how complex an affair memory is and how basal it is for all our important human interests. C. Disintegration of Memory in Old Age. — When mem- ory begins to decay under the advance of age there is a remarkable uniformity in the order in which certain kinds of knowledge disappear, and in many cases of insanity a similar order of disintegration is observed. Thus, the mem- ory of proper names is among the earliest of the losses, and the MEMORY 235 more concrete are our ideas, the earlier do we lose the memory of the words for them. Abstract ideas which depend very largely for their existence in our thought upon the words which we use to designate them are by virtue of the law of habit much more persistent; because the word is in this case bound up much more widely and intimately with our use of the idea. So it comes about that the memory of adjectives and verbs, conjunctions and prepositions, outlives that of most nouns and proper names. The objects for which nouns are our verbal symbols we can, and frequently do, think of in terms of imagery other than that of words, e. g., visual, tactual, etc. Consequently the memory of these words is less deeply imbedded in the brain tissues, and when this tissue decays such memories are the first to suffer extinction. It is a familiar fact too that old people are much more forgetful of recent occurrences than of those which happened further back in the past. This is no doubt attributable to the loss of normal receptivity by the brain. It retains fairly well impressions made upon it at an earlier period, but it cannot now take on new ones. D. An Illusion or Memory. — Another curious disturbance of memory, with which most of us are familiar, is found in the experience of an impression that we have previously been in the place where we are at the moment, or a conviction that we have previously said the words we are now saying, while as a matter of fact we know that we cannot possibly have been in the given situation, nor have spoken the words. Many explanations have been advanced for this phenomenon, ■which still remains, however, obscure as to its origin. It probably arises from different causes at different times, and is, perhaps, most often to be regarded as primarily a disturb- ance of emotional processes connected with the 'familiarity feeling.^ It is in that case a kind, of emotional illusion in which the organic reaction normally elicited by familiar situ- ations is vigorously stimulated by soin.e inappropriate object. 236 PSYCHOLOGY Individual Differences in Memory. — Common observa- tion as well as careful experimentation indicates the widest variation among people as to the materials which they employ in their memory processes and also as to the proficiency which they display in acquiring and retaining information. With- out attempting a complete survey of these differences, we may at least mention certain characteristic ones. We have hitherto commented upon the preferences which given persons evince for definite forms of imagery as compared with other forms. This need not be repeated, although it evidently will appear in the memory activities. Certain people can remem- ber much better things which they see than they can things which they hear and vice versa. The basis of these prefer- ences as to the source from which information is obtained in most cases can only be inferred with uncertainty. Apart from the question of the preference for a special sense or a special form of imagery in the exercise of memory, we find that certain people can learn very quickly but cannot retain long what they learn. Others can acquire only very slowly, but they retain firmly what they get. Others less fortunate than either class, can neither learn quickly nor retain effect- ively the information they try to obtain. A few favoured persons learn with great quickness and retain what they get with a tenacity and permanence which is utterly exasperat- ing to the ordinary plodder. We shall discover some of the grounds for differences of the kind last mentioned when we discuss the training of memory. Now and then a remarkable individual is discovered who altogether out-strips in some special direction the memory capacities of the average man. Some chess players have memories of this kind, enabling them to play while blind- folded a dozen or twenty games at once. Similarly the abil- ity to remember page after page of numbers is met with, and this too after but a single reading or hearing. Musicians have occasionally remembered from a single hearing long and MEMORY 237 complicated scores. It is somewhat comforting to the com- mon-place person to know that these prodigies are ordinarily no better than, and often quite inferior to, the average indi- vidual in all other uses of their memories save the one which gives them notoriety. Training and Bevelopment of Memory Processes. — A good memory, in the practical sense of the phrase, would seem to depend upon (1) ease and rapidity of acquirement, (2) permanency of retention, and (3) the ability to recall information promptly and accurately when wanted. These results clearly involve (a) the original act of impression, (b) the process of retention, and (c) the act of recollection. The original impression and the act of recollection are under our immediate control. The process of retention, once a stimu- lation is given, depends upon the brain tissues, whose con- dition we can improve only indirectly by giving ourselves healthful habits and hygienic surroundings. In the inter- ests of brevity no effort will be made to treat separately these three factors in efficient memory activities. The reader, who desires so to do, can easily assign the facts canvassed to their appropriate compartments. A. Repetition, Vividness, Recency, and Eiumber of Asso- ciations. — It is evident that any effort to train the memory must, if it is to succeed, be based upon the employment of such principles as are natural and inherent in the memory process itself. ISTow one of these principles primarily con- cerns repetition and involves factors which are largely mechanical in their nature. If the cortical basis of reten- tion is resident in the modifications of nervous tissue, brought about by the impressions which pour in upon us, it is clear that anything which will augment the permanency of these modifications, or increase their number, will in so far make towards the preservation of the accompanying psychical proc- esses and the establishment of an efficient memory. Experi- ence certainly justifies this statement, for we find that any 238 PSYCHOLOGY impressions which we can make extremely vivid are likely to be retained in memory for a longer time than would be the case if the impressions were less intense. Such vivid experiences are always productive of deep-seated neural excite- ment, and we may reasonably suppose that their ready retention and recall is a sign of the depth of the nervous modification produced by them. Similarly, the mere repeti- tion of an imj)ression must serve sooner or later to set up relatively permanent modifications in the brain tissue, and so indirectly accomplish permanency of retention in the mind. Temporary effects can be produced, as every schoolboy knows, through the influence of recency of stimulation. Cramming for examinations, when successful, rests largely on this foundation. These points, together with the others men- tioned in this section, have, with a single exception, been already touched upon in our account of association in the previous chapter. It is not often easy in a practical way to enhance the effect- iveness of our memories through rendering emotionally vivid the impressions we wish to preserve. But so far as we can succeed in focalising our attention exclusively upon the matter in hand, so far we do make gains in vividness, and the importance for efficient memory processes of concentrated attention is based precisely upon this fact. Speaking from an empirical point of view, it seems probable that the immense variation in the memory processes of different people is largely connected with this difference in ability to concentrate atten- tion. The habit of giving oneself with complete abandon to the undertaking immediately in hand is one of the most significant clues to the securing of an alert and accurate memory. Moreover, this concentration of attention is as significant at the time of recall as it is at the moment of original impression. Obviously it is simple enough to make use of repetition. We may either do this by giving ourselves over and over again MEMORY 239 the same sense stimulation, as when we repeat a name which we wish to remember; or we may, after the manner of the modern elementar}'' schools, present the same object to a number of different senses, as when we listen to the sound of the name, then speak it, then write it and look at the written word. In such ways we can increase the depth of the cortical modifications, corresponding to some single sense department, or we can increase the number of cortical areas affected by the stimulus. In either case we evidently increase the total amount of cortical modifications, and so better the chances, not only for permanent retention, but also for easy and ready recall. The more pathways there are in the brain leading to the stimulation of any special activity, the more likely is it that the given activity can be promptly aroused. The more ideas there are in the mind connected with any given idea, the more chances there are for the ex- peditious production of the latter when needed. As a matter of fact all memory processes depend in some measure upon this mechanical factor, but it becomes relatively less important as the general level of intellectual development rises. There are many things which children must neces- sarily get at first in a largely mechanical fashion. Learning to spell, for example, is in English mainly a mechanical accomplishment, the available rational elements being chiefly conspicuous by their absence. But for adult undertakings it is a poor memory which responds only to mechanical incite- ments. Kevertheless, our modern education, with its exten- sive desertion of all verbatim methods of memorising, ia undoubtedly in danger of pouring the baby out with the bath, of discarding a method useful in its place, even though not useful in all places. B. Logical Method of Memorising. — The most important factor in assisting the establishment of broad and effective memory processes is of a practical and logical character. If we can once knit up a fact to be remembered with a group 240 PSYCHOLOGY of other already known facts with which it is intimately related, we often come to see the members of the entire group as mutually dependent upon, or explanatory of, one another. And thus we find we can retain in memory the total mass more eflBciently than we could a much smaller number of items, so long as they remain unrelated. Such an interrelating of the facts has in a sense the effect of reducing the mass to a single mental fact. A child being taught the method of long divi- sion in arithmetic, or the method of determining the square root of a number, finds the successive steps in the process extremely difficult to keep straight, so long as the procedure is based simply upon the memory of the rule, which states dogmatically the order of the various operations to be per- formed. But as soon as the relation of the several steps to one another is clearly apprehended, as soon as the real nature of the process is understood, the verbatim memory of the rule becomes a superfluity, which may be forgotten with entire impunity. The several facts represented by the separate arithmetical operations all flow together as integral parts of a larger whole, to which the}'' are seen to be essential. Thereafter, the nightmare of a forgotten rule is banished. In a certain sense, however, the rule can hardly be forgotten as long as the clear apprehension of the relations involved remains. For the rule is simply the verbal formulation of these relations. But under such conditions one's action is free, intelligent, and independent, instead of blind and slavish to a mere rule-of-thumb. If we are asked how to go about the creation of these logical relations among the facts with which we wish to equip our memories, the answer will turn upon two points. We must first reflect upon the thing to be remembered, and attempt to give it a setting among the things with which it is most closely connected. ISTo fact ever comes to us wholly isolated from the rest of our knowledge, and most facts bear upon their faces evidence of their most intimate relations. We should MEMORY 241 at once, then, scrutinise each new fact that comes, and inquire what there is in the series of events or relations to which it belongs that has occasioned its existence. We should ask for the causes which have produced it, and the consequencea to which it leads. If we can succeed in setting up relation- ships of this kind, we find that the new fact becomes a real part of our minds, just as in the case of the arithmetical rules of which we spoke a moment ago. In studying history, for example, such a procedure will mean that we shall try to see any given fact, like a battle, a cession of territory, or a piece of legislation, in the light of all the facts, political, social, economic, geographical, etc., which may bear upon it in any significant way. All the important episodes in an his- torical period will thus be welded together, each throwing light upon the other in a way which makes it natural and •easy to recall them. An ideally perfect mind would involve, among other things, a complete working out of all the relations sustained by a given fact to all other known facts. In actual experience, however, we find that our information is largely stored away on the compartment principle. Our knowledge of history seldom gets any very intimate articulation with our knowledge of astronomy. The events with which each deals do not appeal to us as intrinsically germane. Similarly, our knowledge of exact science seldom interferes in either a theoretical or a practical way with our knowledge of politics ; and it is notori- ous that, for certain persons at least, religious knowledge and belief are kept quite distinct from every other intellectual and practical interest. In the second place, we should always, when possible, pro- ceed at once to make some actual use of the information we are seeking to impress upon our memories. In a certain way the process of reflection, which we have just been describing, necessitates our using the facts we are trying to memorise. But we have in mind here a more overt activity. "We saw in 242 PSYCHOLOGY the previous chapter that the fundamental function of ou? memory and imagination is the control which they afford over experience, both past and future. These activities are, more- over, only a sort of half-way house between the sensory stimulus and the motor reaction, of which we have heard so much. The relevant motor expression ought, therefore, to be allowed to occur. If all this be true, we shall have some theoretical foundation for the precept we have just formu lated, a precept which is abundantly justified by experience. The sooner and oftener we can apply to some practical under- taking a fact we wish to remember, the better the chance of its remaining in our minds. Talking about it, writing about it, incorporating it into some manual constructive activity, if it is a fact which will permit such treatment, are all methods of accomplishing the desired result. A mind trained to concentrated logical reflection upon facts, and then further trained to make the earliest feasible application of them in practical ways, is a mind ./hich will achieve the maximal efficiency of which it is capable. Ease and rapidity of acquire- ment, promptness in recall on demand, and permanency of retention will all be at their best. C. Mnemonic Systems. — Evidently these methods of train- ing the powers of retention and recall suggest no easy royal road to success. They mean hard work. But they are the only methods which have any large and general significance for the development of the mind. Many catch-penny devices have been hit upon to simplify memorising, and within certain nar- row limits such systems have a value. The mnemonic schemes of many so-called " memory systems " illustrate the point. Suppose one has occasion to remember a great many unrelated numbers, like the street addresses of a large group of people. One may greatly facilitate such a feat by first memorising a " form," in which each digit is connected with a consonant, e. g., the 1 with t, 2 with I, 3 with d, etc. The next step is to make a word easily suggested by the person whose house MEMORY 243 number is to be remembered, in which these letters shall occur in proper order. For example, Mr, Smith's number is 122, Mr. Smith is tall. The word tall in the number form means 122, for the vowels are neglected. For special purposes, such as that of our illustration, such methods can be made very useful. But as applied to the acquirement and retention of miscel- laneous information they are failures. It requires more time and effort to learn the forms, or frames, and then make the applications, than is required to accomplish the same result in the ways we have already pointed out. Idiosyncracies in Form of Eecall. — Many persons have curious individual peculiarities in their methods of recalling specific kinds of material. Thus, certain people always think 100 "y Fig. 61. In this form the numbers are seen extending upward and to the right from about the level of the shoulders. of the numerals by means of a kind of visual framework, known as a number form. These number forms are most various in their shape and size and general character, some of them being seen as coloured in many hues. An example of one of the simpler types is given in the accompanying sketch. (Figure 61.) A person possessing one of these forms always sees the numbers about which he is thinking appearing in their appropriate place in the framework. Other persons always think of the months of the year, the days of the week. 244 PSYCHOLOGY and even the hours of the day, in similar visual frameworks. All these devices seem to represent the effort of the mind to give a concrete basis to abstract relations. But they are for the most part acquired in early childhood in a perfectly naive way, and apparently indicate native differences in the way different minds get hold of material to be remembered. " Coloured hearing," or chromgesthesia, of which mention was made in the analysis of perception, belongs to the same range of individual idiosyncrasy. CHAPTER X THE CONSCIOUSI^ESS OF MEAmWG AND THE FORMATION OF CONCEPTS In the actual execution of the functions hitherto described another mental operation is involved in addition to those which we have thus far analysed. This operation is contained in a latent fashion in each of these conscious activities with which we have been dealing; but it conies repeatedly to light as a relatively distinct mental process, and we must accord- ingly submit it to examination. Indeed, many of the acts which we have used as illustrations throughout our previous study could hardly result as they do were it not for the pres- ence of this mental factor, which is known in its most devel- oped form as conception. The mental product which results from it is called a concept. In its more rudimentary form we may call it the consciousness of meaning, and we shall discuss the simpler phase first. The Consciousness of Meaning. — On the side of function, the most fundamental property of intelligence is, perhaps, the ability to recognise and emjDloy meanings. Perception could never lead to the establishment of efficient habitual coordina- tions were we not able to apprehend the meaning of that which we see and hear and touch. Memory would be an abortive resuscitation of the past could we not recognise the meaning of that which we recall. Imagination in all its forms would be a mere mental logomachy were it not for our ability to understand the meaning of the images which occupy our minds. We shall later see that volition, or conation, depends from the very first on the use of meanings. From the beginning to the end, therefore, of our mental activities the presence of meaning is absolutely indispensable. 246 PSYCHOLOGY That a thing means something to us is equivalent to saying that it symbolises something for us, that we are aware of some of the relations which it sustains to other things. Now, the mind shows itself from the very outset as a relating activity. We have previously analysed one of the most elementary forms of this relating process in our account of recognition. On the level of j)erceptual and sensory activities the crude, vague identifying of one experience with an antecedent one must represent in the infant consciousness the first outcropping in an explicit way of the relational factor, the first appearance of the awareness of meaning. An experience v/hich is recog- nised, no matter how vaguely, is thereby in our very manner of feeling it connected by us with something else not present. Meaning in Sensory Material.— The manipulation of the sensuous material of experience — now in an analytical, dis- criminative way, and now in a synthesising, associative way — > results inevitably from the very first in the disclosure of innumerable relations involved among masses previously sensed in a rude, inchoate manner. Certain typical forms under which this analytic-synthetic development of relations occurs, we have already described in the chapter on attention, so that we need not repeat the matter at this point. "We are emphasising here, however, as we did not do at that juncture, the fact that our noticing of differences and like- nesses in the material presented to our senses rests upon our ability to note and employ the relations which these proc- esses of attention throw into relief. It is, in short, because the elements which we thus break out from the total mass of unanalysed sense experience possess meaning for us, symbolise relations of one and another kind, that we can employ them coherently and efficiently. Without this element of appre- hended meaning they would remain disconnected, wholly irra- tional and inert bits of mentality; curious perhaps, but cer- tainly useless. The element of meaning joins them to one another in a vital organic union. • CONSCIOUSNESS OF MEANING 247 Pure sensation can be thought of as bare material wholly devoid of meaning, a mere "that" ; and we can similarly con- ceive of sheer meaning disconnected from all imagery or sensory stuff. In actual experience we never meet either condition. Sensations always have some meaning however rudimentary, and meaning is always draped upon some carrier, whether image or sense process. This statement is certainly true of all strictly conscious activities. Whether rational processes may occur by means of sub-conscious cerebral action and without conscious manifestations is quite another question. Probably the most fundamental form of this consciousness of meaning and relation is our previously mentioned aware- ness of sameness and difference. We know at once without tutelage of any kind when two experiences seem to us the same, and when they seem different. Evidently, the process of recognition is closely related to this sense of sameness, if it be not, indeed, found practically identical. Meaning in Ideational Processes. — All that we have said, thus far, about sense perception and the analytic-synthetic play of attention upon such material is true in even more obvious fashion, when we come to speak of images and ideas. The idea is, as such, clearly a symbolic affair, finding its raison d'etre not in itself, but in that which it does, that for which it stands. Evidently meaning is the very essence of the idea. Moreover, we develop the meanings and relations am'ong our ideas by means of just the same kind of attention processes as characterised our manipulation of sensory activi- ties. By focussing our attention now upon one feature of a thought, and now upon another, by " abstracting," as it is sometimes called, one phase or another, we analyse our ideas, compare them with one another, and so come to the discern- ment of unsuspected relations, of unrealised likenesses and differences. Psychological Basis of Meaning. — Psychologists are by no 248 PSYCHOLOGY, means agreed as to the precise nature of the mental activity by means of which we apprehend relations. Certain writers m^ke the whole achievement a function of attention, and dis- claim the necessity for any further explanation. Attention is declared to be in its very essence a relating activity, and consequently, so far as we attend, we always attend in a relational way. Other writers maintain that just as certain moments of consciousness are cognisant of percepts or images, so certain other moments are cognisant of relations. Thus James speaks of our having " feelings of relation," e. g., a feeling of " and," a feeling of " if," and a feeling of " for." Certain psychologists of this way of thinking recognise what they call " relational elements " of consciousness comparable with sensation elements. A complete consideration of this matter would take us too far afield into unsettled principles, and the reader must temporarily countenance the author's dogmatic general state- ment that the consciousness of relation is a basal factor in all activities of attention; that our attention is sometimes more, and sometimes less, directed toward the extant rela- tions than toward the things related; but that no moment of cognitive consciousness is wholly lacking in the awareness either of relations or objects. The distinction between objects and relations simply names two features, the static and the dynamic, of a common phenomenon. The relational proc- esses are perhaps best characterised as attitudes. The mind is in a different condition of expectancy after hearing the word "and," from that which it manifests after hearing the word "if." These difPerences are no doubt often reflected in different overt motor acts and perhaps always by different nascent ones. Some of these motor expressions will be found appearing in the checking and releasing of the breath, as anyone may verify for himself. "We come next to consider conception, which constitutes the most overt and elaborate form assumed by our consciousness CONSCIOUSNESS OF MEANING 249 of meanings a form in which psychologists and philosophers have always been specially interested. The Nature of Conception. — In our illustrations of the man- ner in w'hich we consciously avail ourselves of the lessons taught us by experience, we have implied that memory and imagination operate by summoning specific events which apply to the problem immediately confronting us. This is often the case. Thus, I find myself puzzled as to the best method for getting to some very remote country town. I attempt to recall what railroads I employed to get there a year ago, and I solve my problem by applying the recollection which comes to me of this particular achievement. I remem- ber that I took the A and B to junction D, waited two hours and got a train on the X and Y to my destination. But many cases in which we apply the fruits of past experience are of a different order from this. Thus, if I am purchasing scientific instruments from a French firm, I must convert the prices in their catalogue from francs into dollars. This I accomplish by first bringing to mind my idea of a franc, as being approximately a fifth of a dollar, and then performing the appropriate arithmetical operation. In this case I obvi- ously employ my memory in meeting my necessities; but it is memory in the form of reproductive imagination upon which I fall back, and not necessarily the memory of any single event or experience, as in the preceding instance. Again, I am interested in certain philanthropic efi'orts at social reform, and I find that the programme which I am invited to support involves belief in the hereditary nature of acquired characteristics. The theory at issue maintains that vicious traits are acquired and transmitted from parents to children, and my contribution is solicited in the furtherance of a project to prevent the possibility of sueh acquirement and transmission. Immediately I find my mind busying itself with the idea of heredity, and my final action is, perh-aps, determined by the conclusion which I am able to reach upon this point. 250 PSYCHOLOGY Now in these last two cases my use of the idea of a franc or my idea of heredity clearly does not necessarily involve an immediate reference to any single and specific experience of francs or heredity. I might, of course, make the applica- tion in this way, if I chose. I might allow my mind to dwell on the last occasion upon which I sav*^ a franc, and on the last book in which I had read of heredity. But this is by no means essential, and often would not occur under such cir- cumstances as we have supposed. Accordingly, these ideas, to wit, franc and heredity, are mental devices by which we succeed in symbolising for ourselves in the one case a num- ber of objects, and in the other case a number of relations, without the necessity of calling to mind any particular occa- sion upon which we have come in contact with them. We use these ideas fearlessly in our reasoning, and when we have reached our conclusions we make the application to the con- crete instance in hand, with entire confidence that the event will justify our action — and generally it does. Such ideas as these are what are usually called concepts, and taking such cases for the moment as reliable illustrations, we may say, following the common usage, that conception is that mental operation hy means of which we hring together the common points of our various experiences and mentally consolidate them into ideas; ideas ivMch ive are then able to use as sym- bols, or representatives, of these manifold items. We apply the term " concept " to this idea, the term " conception " to the mental operation in which the idea is produced. The derivation of the, word concept (from concipere, to take in) may assist us to bear the facts in mind. If concepts are general ideas of the kind we have indicated, it is evident that we must possess them in large numbers. Concepts of men and horses, houses and trees, hats and tables, with others of like ilk, must constitute a large part of our mental furniture. We must also have concepts of such things as colour, odour, and sound; concepts of physical relations. CONSCIOUSNESS OF MEANING 25 1 like position^, order, and time; concepts of moral attributes, such as good and evil, and dozens of other forms too numer- ous to mention. We shall probably get ahead most rapidly in our analysis if we take some special instance of conception and examine the mental processes involved in it. Take in this way one's general idea of horse. Concept and Image. — If I say to a group of persons, " Fix your attention firmly upon your idea of horse,'' a cer- tain number of them are sure to find a visual image of a horse arising in their minds. Another group will find that the auditory-motor word-image " horse " is present in their consciousness. IsTow, according to our definition, the con- cept of horse must not apply to any special horse, but it must represent all horses. How can the persons who are confronted with a visual image of some particular Bucephalus, or Eos- inante, be said to have any concept of horses in general ? The correct answer to this question is at once suggested by a ref • erence to the imagery of the second group of persons. The word-image " horse " evidently does not pretend ta refer to any one specimen of the horse more than to another. It is purely symbolic. When it comes into our consciousness to serve as a concept, it is as though we had agreed mentally with ourselves to accept it as a representative of the physical equine genus. Just as in algebra we allow the early letters of the alphabet to stand for certain quantities in our prob- lems and the later letters for certain others, making the appropriate practical substitutions at the completion of our computation, so here we symbolise certain objects to ourselves by means of auditory word-images. We mentally manipulate these image-ideas, draw certain inferences and then execute the substitutions, which in these cases are commonly overt acts. Having, for example, reflected by means of such con- cepts upon the shortcomings of horses, we decide to purchase an automobile. The concept, which is primarily mental, is eventually converted into movements which are physical. 252 PSYCHOLOGY Now, the case of the persons who use visual images is in no respect fundamentally different from that of these users of word imagery. The visual image may, to be sure, for bet- ter or for worse, be a kind of copy of an individual in the class which it is supposed to represent. At least it is often a recognisable copy of one of our perceptions of such an indi- vidual. But provided that, in our use of an image, we rec- ognise it as really symbolising the class, and not an indi- vidual, and use it intending it to accomplish this purpose for us, it is a matter of considerable indifference what special kind of imagery we happen to employ, whether visual, or auditory, or motor. Of course word images are freer from the possi- bility of suggesting misleading concrete details than images of other varieties. But even they may be vitiated by erroneous implications of one or another kind. We shall now and then meet persons who will insist that their idea of horse does not involve any detectable imagery of an}^ kind. They "Just know" what horse means and that is all there is to it. People of this type represent several forms of reaction. In many instances this report is due solely to introspective obtuseness and lack of practice in detecting mental processes. "With some the imagery is of a fleeting vocal-word character which they readily overlook. With cer- tain ones there may be a suppressed pronunciation of the word and beyond this they employ no thought machinery at all. In a few cases there exists a very subtle form of motor imagery, or even overt movement itself may be used. The nascent movements, or images of movement, may be con- nected with the conceived object in any way whatever. They may, for example, be tracery movements of hand or eye. Anything to which the meaning ^Tiorse" can be attached will serve. Two important points emerge from the preceding examina- tion. (1) The concept normally involves an image, whether concrete, verbal, motor, or what not. A substitute for the CONSCIOUSNESS OF MEANING 253 image in the form of nascent movement may possibly be employed at times; (3) Whatever image we use, it is the specific meaning which we attach to it that constitutes it a concept. These two considerations make clear how it comes about that our thought processes seem often so different on different occasions, even when we have been thinking about the same subject. Of course, the order of our thoughts might easily vary at different times, and our conclusions might vary. But how is it that we can think about the same things when the content of our thought is so different? The content of our thought is, so far at least as concerns the knowledge process, largely made up of imagery. To-day this may be principally auditory and verbal, to-morrow largely visual. It may be on the one occasion vivid and detailed, on the other evanescent and wholly schematic. But provided I use the different images to stand for the same meanings on the two days, I shall come out perfectly well and my thought will unquestionably have been about the same object and its rela- tions. Thus it comes to pass that, although we never have literally the same image present twice in our consciousness, we nevertheless can think the same meaning again and again. The Generic Idea. — This seems the appropriate place to refer to a theory which certain eminent psychologists have espoused, L e., the theory of generic ideas. The hypothesis upon which the theory rests is that our repeated visual per- ceptual experiences of tables, for example, result in producing a kind of composite mental photograph of tables. Such a composite photograph would evidently serve us whenever we wished to think of tables in general; that is to say, it would serve as a concept. We might use other images for the same purpose, conspicuously our word-images ; but we might equally well use this composite visual image. It is held, therefore, that the generic image is a sort of embryonic concept, more concrete than the true concept, but less concrete than the images of particular objects; in short, a, transition form.. 254 PSYCHOLOGY We shall make only two comments upon this theory. In the first place it is extremely difficult to determine whether or not we really have such composite images. It would obviously be very difficult to say with entire confidence whether an image possessing the indefiniteness of outline and the indistinctness of detail which a true composite would undoubtedly possess, were actually a representative of innu- merable individual perceptions; or simply a blurred^ vague, imperfectly reinstated image of some single perception. In- trospectively, that is to say, the evidence can hardly be made conclusive in support of the theor}^ Moreover, the brain processes involved in the production of such an image are somewhat difficult to understand when brought into connec- tion with our supposed ability to call up images of specific objects belonging to a given class, of which we might also have a generic image. However, there is perhaps nothing impossible about the theory. In the second place, so far as concerns the function of conception, it appears at once that such a generic image would belong to the class of images which we may call " copy- images," in distinction from images which purport to be merely symbols. All images, are, of course, symbolic, so far as they stand for something not themselves, and all images are copy-images so far as they serve to reinstate special forms of sense perception. An auditory image may be in this way a copy, good, bad, or indifferent, of an acoustical perception. A visual image may likewise simulate some visual perception. But the auditory image may, on the other hand, serve to symbolise some visual experience, and the visual image, e. g., the visual image of a word, may also symbolise something of a non-visual character. Evidently, copy-images may be hope- lessly inadequate, as copies, to stand for generalised relations. So, to revert to our original illustration, a visual image of a table would, as a mere copy, be an unsatisfactory representa- tive of the class "table," for no single image could embody CONSCIOUSNESS OF MEANING 255 all th.e peculiarities of all tables. This limitation would be as true of the comjDosite image, supposing it to exist, as of any other. It is only as such an image is employed sym- bolically that it serves satisfactorily as a concept of the class *' table/' But an image of any table whatever would serve this purpose well enough, provided only that in our thinking we used it with this recognised intention. Furthermore, the word-image, which commonly has no resemblance whatever to the objects symbolised, is always available. So that taking account of these considerations — the doubt as to the actuality of the generic image, and the absence of any special fitness in it for service as the basis of a concept — we may safely omit further discussion of it. Conception and Language. — Our analysis of conception has brought out the fact that it is by means of this mental proc- ess that we are able to make our thoughts the vehicles of definite meanings. It is a familiar fact that language has a precisely similar function. The inference at once suggests itself that language may be nothing but an elaborate con- ceptual system, and this inference is essentially correct. When we communicate with others we give our ideas outward expression in spoken words, which serve as concepts to the hearer. When we are engaged in reflective thought, we shall often find that we are thinking in terms of word-images, and these word-images in such cases serve as our concepts. Lan- guage is thus not only the great social medium of thought exchange, it is also in large measure the medium of subjective thought processes. Some psychologists maintain that all concepts are of the language variety, and philosophers formerly contended that no reasoning would be possible without language. Both of these views are undoubtedly too extreme. We do sometimes reason, and we may have a considerable number of concepts, without resorting to verbal language. !N"evertheless, the supple- mentary statement must be made that language is the great 256 PSYCHOLOGY conceptual mechanism, and that we depend upon it far more than upon any other mental material for conveying our mean- ing, not only when we commune with others, but also in our own private thinking. In the use of spoken language, as well as in the use of verbal images when we are reflecting, the thought process is often so rapid that we have no distinct consciousness of the words as such. The stress of our interest and attention is upon the meaning which we are seeking, and this seems often to attach to the verbal activity in its entirety as a sentence, or a series of sentences, rather than to the isolated words. This fact does not, however, prejudice the truth of our gen- eral assertion that words serve as our most important con- ceptual symbols. Theories of the Origin of Language. — The origin of vocal language has been connected with a number of influences of which three may be mentioned. (1) Certain emotions lead instinctively to vocal expressions, e. g., the cry of fear and the snarl of rage. In the animal world such expressions are effectively employed as a means of communicating mental states. The theory of the origin of language from such cries is ordinarily known as the 'inter jectional.' (2) When cries of this kind and other natural sounds are imitated to indicate to others the object or condition which naturally produces them, e.g., barking to convey the meaning 'dog,' we have lan- guage in a more genuine sense. The theory that language arises in this way is known as the 'onomatopoetic' It may be more briefly styled the 'imitative.' This theory has been given certain very subtle elaborations into which we cannot go. Both the interjectional and the imitative theory empha- sise presumably true stages or factors in the process of lin- guistic development. The first probably indicates correctly the source from which the material of language is drawn. The second designates one method at least by which this material gains real linguistic properties. (3) We may add the CONSCIOUSNESS OF MEANING 257 prescientific doctrine that language was giveii to man by direct act of Providence. Vocal language is originally not different in character from visible gesture which is quite competent to convey meanings and has from the first been employed for this purpose, wit- ness the practice of animals, primitive peoples, and deaf- mutes. Indeed, everybody uses such gestures to supplement the meaning of words. Among cultured peoples this is espe- cially true of the Latin races. Like all concepts, one of the most useful functions of the developed word is to suggest attitudes without the necessity of filling in details of mean- ing with concrete material. Words still retain therefore their primitive connection with gesture and attitude.* Language in Relation to Particular and General Ideas. — The conceptual use of language brings readily to our notice certain facts which bear significantly upon our present topic. We defined conception as a process of forming general ideas, and this seems to be the most striking feature in the process. But if words can be regarded as concepts, we must have con- cepts of individual objects as well as of classes; or at all events our method of thinking individual objects must be similar to our method of thinking classes. This is, indeed, the fact. We really have a concept of Jupiter, as well as of gods; a concept of earth, as well as a concept of planets; a concept of this particular book, as well as of books in general. *The choice of vocal movements rather than some other form of movement to serve the language function has been connected with various causes. We know that excitement produces muscular changes. The respiratory muscles are especially easy to affect in this way, and in large air-breathing animals at least audible sounds are inevitable consequences of such disturbance. Moreover, the vocal cords have no other important function to be interfered with by their vocal use for language. Sound is better material than light, which is its only serious competitor, for use in direct communica- tion, for it is more independent of constantly recurring conditions, e. g., darkness and intervening objects. These and other similar reasons probably account for the adoption of vocal sounds for lin- guistic uses, although such selection may in the first instance have involved very little of conscious choice. (Cf Judd, Psychology.) 258 PSYCHOLOGY We have only to remember that conceptioii is after all at bottom simply a mental process of designating meanings, to see that we can in this way indicate any meaning we wish; e. g., the meaning of a single object or a dozen; the meaning of a mathematical relation, or of an historical relation; the meaning of a familiar object, or of an impossible one. In each and every case we shall have a concept, and in most cases a word, or a word-iimage, will be a very convenient device by means of which to think it. We may easily connect the process by means of which we gain concepts of single objects with the process by means of which we obtain general ideas of classes of objects, if we observe that in both cases we have simply set a boundary line about certain things; in the one case the boundary contains one object, in the other it contains an indefinite number. But in both cases our mental act has been the distinguishing of one kind of meaning from all other kinds of meaning. That form of the process in which our idea refers to some common property, or properties, of a number of experiences, like hardness, or blackness, or goodness, has commonly been regarded as the true type of conception, because we appear in such cases to have abstracted the common qualities of a number of events, then generalised upon these, and so obtained the concept, or general idea. But the process by which we reach a concept of a single object involves abstraction just as truly, if not so extensively, as the previous form of opera- tion. To obtain a concept of London involves setting the idea of London ofE against all other ideas; involves abstract- ing it in a perfectly definite way. In a sense, too, our concept of London is just as complete, just as universal, as is the concept city. It applies to all of its object, as truly as does the concept city, and it is in a measure an accident, an irrelevant incident, that the total object re- ferred to is, from the practical point of view, singular and not plural. CONSCIOUSNESS OF MEANING 259 The process by which we actually come into possession of some of our more abstract general ideas is, perhaps, more complicated than that by which we gain our concepts of par- ticulars. But the fundamental distinction between the two kinds of concepts, after we have attained them, resides in the fact that the one emphasises points of identity and sameness among the various elements of our experience, the other emphasises primarily points of difference. Strictly speaking, then, we may be sure that we have concepts of single objects, as well as of classes of objects. We have, also, concepts of abstract attributes, concepts of relations of all kinds. There is no meaning of any sort accessible to our intelligence for which we may not have a concept. Indeed, in the broad sense of the term, every idea is a concept. On the whole it is, perhaps, easier to follow the older usage and to retain our original provisional definition of the con- cept as a generalising idea, and then to remember tl at such ideas sometimes generalise, so to speak, upon single objects, qualities, or relations, rather than to recast our definition, which would then vary somewhat ambiguously from that traditionally employed. After all, the fundamental points about concepts are those we have already mentioned, which evidently remain untouched by these questions of the number and character of the objects to which the concepts refer: that is, (1) the existence of the concept as a concrete thought, which we call an image or idea; and (2) the use of this image-idea to convey to ourselves, or to others, some definite, recognised, and intended meaning. Scientific Concepts. — It should, perhaps, be remarked at this point that the scientific and logical concept is generally credited with a higher degree of exactness and precision than our definition suggests. The concepts of science, such as "metal," are gotten by a process of abstraction and com- parison, the result of which is then expressed in the most rigorously exact verbal definition. Evidently, however, these 26o PSYCHOLOGY are not the concepts of practical life. Scientific concepts are outcomes of definitely reflective processes, whereas the con- cepts of daily life have many of them originated in the rough "give and take" of practical experience, without any explicitly reflective deliberation at all. The General Function of Conception. — 'The general func- tion and value of conception in the economy of the psycho- physical organism is probably so obvious as to require no further elaboration. It may be described as the great sim- plifier of mental operations, the labour-saving device by means of which we are enabled to accomplish with single ideas the work which otherwise might require the cooperation of many. It only remains to call attention afresh to the fact that the mental capacity which permits this condensation of the meaning of many experiences into the meaning of a single image is generically one and the same with that apprehen- sion of meaning which renders perception intelligible, imag- ination significant, and memory coherent. Neural Process and Conception.- — So far as conception involves imagery, it necessarily follows that it depends upon the reaction of those areas in the cerebral cortex Avith which the several sense organs are most immediately connected. Be- yond this we can say very little, save that there seems some reason to believe that all the more reflective and ratiocinative forms of thought process involve in an important way the action of the Flechsig association centres. It must be frankly admitted that at the present moment the neural counterparts of these higher and more recondite phases of psychical activity are practically unknown. It seems clear that they must in large measure involve the action of the same areas that are concerned in perception and in simple acts of memory. But the nature of the differences in the form of the nervous action, when the psychical act is one of pro- longed reasoning with the use of elaborate concepts, as con- trasted with the mere accidental calling to consciousness of CONSCIOUSNESS OF MEANING 261 some familiar visual image, for example, is still altogether a matter of speculation and hypothesis. The Genesis of Conception. — We have repeatedly seen reason to believe that mental life is in all essential respects like other life phenomena, manifesting periods of growth, maturity, and decay. This view leads us to expect a gradual unfolding of the typical phases of consciousness, which are at the outset latent in the infant mind, rather than the sud- den appearance at different times of totally new kinds of mental operation. The development of conception is no exception to this rule. The appearance of a rude type of recognition, which we have discovered to be the prototype of the developed act of conception, may be detected very early in infant conscious- ness. But it is exceedingly difficult, not to say impossible, confidently to designate the precise moment at which the first general idea is elaborated. The facts suggest that babies generalise in a rough way upon their experiences at a very early date. Or, if they do not positively generalise, they accomplish the same result negatively, by failing adequately to distinguish and analyse. Infants a few days old, if given some distasteful medicine, will often refuse utterly for hours afterward to take anything into their mouths, and for indefinite periods will reject the medicine itself. It would probably be absurd, however, to suppose that the baby has at this time a general idea of medicine, although one might with propriety speak of a generalised motor reaction. Nor would such a description detract from the genuinely conceptional nature of the reaction, for the concepts of adults may also he considered as forms of generalised motor activity. As soon as language appears, from the fourteenth to the twenty-eighth month, the formation and growth of general ideas is immensely augmented. But our previous assertion about the connection of concepts and language holds true here, and it is certainly reasonable to suppose that crude general ideas 262 PSYCHOLOGY antedate tlie use of adult language forms. In this connection one must not forget that gestures — for example, smiling^ scowling, clenching the hands, etc. — are often vehicles for conveying conceptual relations, and that the inarticulate cries and vocalisations of various kinds which precede the intel- ligent use of words may also be regarded as primitive lin- guistic concepts. Thus, a certain sound means water, another means milk, and so on. The sign language of deaf-mutes affords admirable illustrations of the same types of expression for concepts. Incentives to Conceptual Development. — The natural incentive to conceptual development is to be found in the needs of the individual. We find ourselves confronted with a situation in which our old ideas are inadequate and unsatis- factory. These are the circumstances which lead children and adults alike to search for new ideas, for efficient con- cepts. JSTew notions in science, new inventions, the slow growth of myth and many of the articles of religious faith have this origin, i. e., the desire for concepts which will enable ns to master a given difficulty, whether practical or theoretical. The development of the concept of number offers a good illustration of the process. Until life has become somewhat complex and organised, number is not needed. Generally in connection with the accumulation of property of some kind the need arises of counting one's possessions in order that loss may be easily detected. Among certain savages this necessity is met by a very small series of numbers and they consequently are unable to count beyond five or ten. In civilised life such a number system would be grotesquely inadequate and the higher numerical rela- tions are demanded, together with the concept of number itself which we thus see has its origin in counting. When we seek illustrations in the range of our formal educational procedure it is not always so clear that the new concepts are gained in response to felt deficiencies in our CONSCIOUSNESS OF MEANING 263 existing stock of ideas. The boy confronted with the con- cepts peculiar to the study of Greek and Latin and mathe- matics would often forego the attainment of them with definite complacency, not to say enthusiasm. It is evident that if he is to master these subjects he must first secure these concepts ; but it would sometimes be a sad j)erversion of the facts to say that the concepts are obtained as the result of a need felt by the boy. A child caught thus in the educa- tional machinery is often whirled about among needs, for which the ideas held out do indeed afford relief, but they are not always needs which the child himself feels. One has, however, only to glance at the history of any specific educa- tional system to recognise that in its inception each system was intended to fit its pupils for some special form of life, and in this vocation the studies offered really had a place. The adult has here attempted to anticipate in the most effectual way the needs which at some time the child is sure to feel. Fortunate the child who is brought up in a system which affords him ideas fitted to his own day and generation, instead of those appropriate to the times and conditions of his great-grandparents. The concepts which we get in the educational system may not always, then, reflect needs and difficulties of which we personally are as yet cognisant. But the system itself is an effort to epitomise the satisfaction of just those needs which in the human experience of the leaders of our race have been felt to be most imperative. Our general statement remains, therefore, essentially true, i. e., that our new concepts arise out of the inadequacy of those already on hand to cope with the conditions in which we find ourselves. The Process of Development of Concepts. — The develop- ment of our concepts after the period of infancy apparently proceeds along two main lines, which we can best discuss separately, although the two are at bottom really one: first, by the creation of essentially new concepts; and second, by 264 PSYCHOLOGY the Gnricliment of old concepts with new material. An important factor in the formation of our concepts, i. e., the process of judgment, cannot be discussed until the next chap- ter, where we shall, however, revert briefly to the conceptual activity. A. Formation of New Concepts. — We have already seen that concepts are primarily based upon perceptual processes, just as memory and imagination are. We have also observed the way in which every perception, even the freshest and most novel, involves past experience. We shall, therefore, be safe in assuming that what we call new concepts are only partially new, and really contain a measure of familiar material. For example, when a boy first studies algebra he is introduced to the concept of the equation, to the concept of symbolism in quantitative procedure, to the concept. of nega- tive numbers, etc. Now, we speak of such concepts as being new to the boy, and so in a sense they are. But we must also recognise the fact that they are not wholly new, and that if they were they would be entirely unintelligible to him. The significance of the equation as a mathematical tool could never be grasped were the boy's previous experience incapa- ble of furnishing him the notion of equality as a starting point. What the boy does in getting hold of such a new concept as that of negative numbers is to compare the new notion with his old idea of number, to remark their likenesses and differences, and to throw into the foreground, by this process of discrimination, the most practically important features of the new case. The result of this procedure is the boy's first concept of negative numbers. These abstracting, discriminat- ing, and comparing activities are present in varying degree in all self-directed attainments of new concepts. This form of development of ideas displays in an unmis- takable manner the essentially organic nature of our knowl- edge. Each idea sprin/rs out of other ideas, which have CONSCIOUSNESS OF MEANING 265 gone before, and in turn gives birth to new successors. The connection is not merely one of sequence in time; it is a connection of the genuinely developmental type, in which one idea is, as it were, unfolded from, and given off by, another. Ultimately, therefore, each of our ideas is related, however remotely, to all the others, a fact which constitutes one illustration of the so-called doctrine of the total rela- tivity of knowledge. Speaking metaphorically, but within the bounds of literal fact, we may say that the great tree of knowledge springs from the seed of that vague consciousness with which the infant's life begins. Differentiation followed by fresh synthesis, old experiences blended with new ones, each modifying the other — such is the course of progress. B. Enrichment of Old Concepts. — Hand in hand with the appearance of relatively new concepts goes the development of our old ideas. This development might be described as having two directions, but in reality the two are one. Our concepts seem sometimes to widen and sometimes to grow more narrow. Thus, we learn more every day about men and women, and so we may truly enough say that our con- cept of humanity broadens as our experience becomes richer. On the other hand our concept of science may, as our knowl- edge increases, become more and more restricted in its scope. Many branches of inquiry which would originally have found place under this heading may, in our maturer judgment, belong elsewhere. Both these processes are, however, simply different modes of reaching an identical result, i. e., the clarification of the precise meaning of our concepts. Every concept is in a sense a working hypothesis, a tenta- tive manner of thinking about things, and is subject at need to revision. Our idea of right is gained in childhood from parental precepts. If we do not stagnate morally, a time must come when we are obliged to reconstruct and modify this childish concept. As our knowledge becomes broader this process of reconstruction may go on indefinitely. This does 266 PSYCHOLOGY not mean that we necessarily discard wholly the idea of right which we received from our parents. Far from it! It means that this idea was necessarily a child's idea, and so inadequate to certain adult experiences; and it becomes necessary to develop it in accordance with the new needs. The incentive to this form of growth in our concepts is, then, precisely identical with that which led to our getting what we call new concepts. It is clear that in a certain sense the process we have just described really gives us new concepts. But practically we think of the new idea as a modification of the old one. The doctrine is sometimes held that our concepts are unchangeable. The difference between this view and the oue we have been presenting is largely verbal. In a certain sense our concepts are unalterable. To use our last illustration again, I can remember what I meant by my childish idea of right, and can recall the idea when I will. In this sense the concept does remain a permanent part of my mental equip- ment, undergoing only such changes as may be due to fail- ing memory. But practically my adult concept which I call my idea of right is, as has just been shown, very different from this childish one out of which it has grown. The Petrifying of Concepts. — That concepts may cease to grow and change is shown by observation of persons who have once settled down into a fixed and narrow vocation in which radically new demands are rarely encountered, and when encountered, are found hopelessly baffling. In a degree this condition is likely to overtake everybody as middle age passes by. The result is too often the pathetic person of inflexible sympathies, circumscribed and dogmatic ideas — ■ the person who is sure the world is going to the bow-wows, and knows it was all much better in his own day. Such per- sons have ceased to get new concepts, and the old ones are inadequate. CHAPTEE XI JUDGMENT AND THE ELEMENTS OF REASONING The mental operations which we have thus far described find the culmination of their development in the process which we know as reasoning. This does not mean that reasoning is a totally new form of psychical activity, to which the others are subordinate. It means that in the process of reasoning the full implication and significance of these other conscious processes come cieariy to light, while in it they reach their completed evolution. Moreover, it does not mean that reasoning is a form of process which appears only after the other processes which we have studied have been devel- oped. Rudimentary reasoning is present from the beginning of conscious life in the human being, and is clearly involved in each of the processes we have thus far analysed. But in the gradual unfolding of consciousness, by means of which it comes to maturit}'', we meet more and more complex in- stances of reasoning, and at each stage we find it involving perception and memory and imagination and conception. At each stage it affords the best index of the real value of these other processes, and in its most elaborate forms it brings out in the clearest possible way their real function. We shall revert to these points more fully later in the chapter. We may define reasoning broadly as purposive thinhing, that is to say, thinking carried on in the interests of some plan which we wish to execute, some problem which we wish to solve, some difficulty which we wish to surmount. The remainder of our discussion will serve to explain an justify our definition. 268 PSYCHOLOGY Analysis of Reasoning. — We are often told that the great educational value of mathematics lies in teaching us to reason correctly. Some hardy iconoclasts have ventured to ques- tion the extent of the value to be gained from the subject on this score, but at least it seems to be universally admitted that mathematics involves reasoning, and we may, therefore, judiciously seek from it an illustration of the reasoning process for our examination. Take the following arith- metical problem, reminiscent of the perplexities of the days of our academic youth. If thirteen melons cost a dollar and forty-three cents, how much should twenty melons cost? Most of us would solve this problem by finding the cost of one melon through the division of one hundred and forty- three by thirteen; and then the cost of twenty melons by multiplying this quotient by twenty. When the problem is distinctly understood, there instantly comes into our minds through our memory habits, the idea " cost of one melon " ; and straightway we find ourselves executing the relatively habitual process of division. This accomplished, our minds immediately turn — again by virtue of our mental habits — to the multiplication of our quotient by twenty. The reason- ing in a case of this kind, therefore, seems to involve the selection of certain ideas out of all those supplied us by the problem, the manipulation of these ideas in accordance with previously acquired habits, and the attainment of the solution by a proper combination of these two processes. So far as there is any originality in such a procedure, we must look for it in the skill and expedition with which we hit upon the right idea to work with, and the accuracy and promptness with which we apply to it the fruits of our previously acquired knowledge. Should we examine a little more closely the nature of these ideas which we employ, we should find that they are clearly concepts. Thus, melon is a concept, cost is a concept, cent is a concept, etc. Were we to give verbal form to the JUDGMENT; ELEMENTS OF REASONING 269 several steps in the process, which we do not always do, we should find that we had such expressions before us as this: one melon eleven cents — eleven times twenty is two hundred and twenty, is two dollars and twenty cents. In other words, we put the concepts together in a form which the psycholo- gists call a judgment. A judgment, when put into words, is what logicians call a proposition, and what grammarians call a sentence. It accordingly appears that a process of reason- ing, such as that of our illustration, contains concepts com- bined in the form of judgments. We have already examined the nature of the concept, but judgment is a new mental operation to which we must now devote our attention. Analysis of Judgment. — It will facilitate our investigation to begin with those cases of judgment to which we give verbal expression, for they can readily be secured in a concrete form, stripped of the introspective difficulties which beset the analysis of other varieties. It will suggest itself at once that, if the judgment is in any measure equivalent to a proposi- tion or a sentence, we ought to gain assistance, in the distin- guishing of its principal forms, from the classifications of the grammarians and logicians. Although the exact meaning of mental judgments and linguistic propositions are not always identical, even where they have the same verbal form, never- theless many of these classifications are undoubtedly avail- able ; and we may expect to find assertative judgments, hypo- thetical judgments, disjunctive judgments, and so on. In the judgment, "the book is heavy," we have the concept heavy united to the concept book. On the other hand, in the judg- ment, " the book is not heavy," we have the concepts appar- ently sundered from one another. Even in this case, how- ever, it is obvious that in the mental state, of which the judg- ment is the expression, the two ideas were together, as truly as in the first case. It is only so far as the ideas refer to objects distinct from themselves that their separation is asserted. In the judgment, " if the storm is severe, the ship 27© PSYCHOLOGY will be imperilled/' we have two pairs of concepts united to one another, i. e., "storm" and "severe/' "ship" and "im- perilled." Like the preceding cases, the ideas are brought together mentally, but the objective union of one pair is made dependent upon the objective union of the other. The judg- ment, "Mr. Smith is either a democrat or a populist/' gives us a typical instance of disjunction. The concept "Smith" is conjoined mentally with the two concepts " democrat " and " populist," and the objective union is asserted of one or the other.* In all these verbal precipitates of judgment Tve seem then to have two or more ideas mentally united in mean- ings which may imply either the postulated union or cever- ance of the objects to which they refer. Analytic-Synthetic Judgments.— Availing ourselves of a further classification which the logicians employ, we may speak of anal}i;ic or of synthetic judgments. "This wood is white," is an instance of the analytic judgment. It exhibits a property of the wood which is inherent in it, and may, there- fore, be said to involve an analysis of the concept, "this wood." "Wood is combustible" is a synthetic judgment, because it adds to the idea of wood the idea of combustibility, which is not immediately, nor obviously, implied in it. We shall pres- ently see reason to believe that synthetic and analytic judg- ments are psychologically really one, and for our present pur- pose we can at least see that they involve, like all the other cases which we have examined, the mental synthesis of con- cepts, whose objective union, or separateness, we mentally predicate. Genetic Relation of Concept and Judgment. — Having dis- *The so-called "impersonal judgment" has caused logicians much controversy. "It rains" is an instance of it. At first sight it appears as though such a judgment could hardly be said to involve a synthesis of two ideas, or concepts, at all. On the whole it seems probable that this form of judgment represents a primitive type of the judging activity, out of which possibly our more elaborate forms have developed. If this be true, the nature of the impersonal judgment will become evident as we go on with our analysis. JUDGMENT; ELEMENTS OF REASONING 27 1 covered in these verbal judgments the constant presence of concepts, it will be well to revert to our account of their de- velopment, and detect, if possible, the relation of the judgment to this process. We observed, when studying the origin of concepts, that they spring out of the mind's effort to mark off, and render distinct, the various meanings with which it has to deal. We saw that in the course of experience these meanings grow in definiteness and scope, so that a concept which meets the demands of childhood often needs for the purposes of the adult either to be reconstructed or else discarded in favour of some more adequate notion. If we examine once again some specific instances of the attainment and development of a concept, we shall come upon an instructive fact concerning the relation between conception and judgment. If we con- sider in this way our concept badness, we find that it has its origin in our very early childish experiences in connection with certain acts for which we were reproved or punished. The notion of parental disapproval quickly became attached to such acts, and, as soon as language could be comprehended at all, we remarked that they received the common appella- tion, ^^ad.'' Unless our account of the memory processes be fundamentally defective, the thought of such deeds should call to mind, in however vague a wa)^, the undesirable conse- quences which had previously accompanied them. At this early stage, then, we must in a nebulous sort of fashion have brought together in our minds the idea of the act and the idea of its effects in the nature of punishment. Such a mental act obviously has implicit in it the beginnings of judgment, i. e., the assertion of a relation "between the mental elements. When, with increasing age, language finally comes to our assistance, we are easily able to apprehend the usage of our elders, and we straightway apply the term %ad" to all acts of a certain character. At this point the idea of badness is for us synonymous with a 272 PSYCHOLOGY certain list of acts with which various kinds of adult dis- approval are connected. When we are inspired to perform such an act, we promptly execute mentally the judging proc- ess equivalent to labelling the act bad. Were we to put our thought into words^, we should undoubtedly have a verbal judgment. All of which seems to indicate with no great uncertainty that the origin of such a concept as "badness'^ is to be found in mental processes which are in their nascent stages crude, vague, undeveloped judgments, involving a rudimentary recognition of relations between certain more or less distinct portions of our experience. We get at these elements of experience mentally by means of rudely distin- guished ideas — in the case of our illustration the idea of the act and the idea of its consequences. Such concepts as this, i. e., badness, owe their creation, then, to elaborations of already attained ideas in a primitive form of judgment. Moreover, if we turn our attention to the subsequent his- tory of such a concept as badness, we find unmistakably, as was pointed out in the last chapter, that its development is accomplished by means of new judgments which are brought to bear upon it from time to time. In childhood, for exam- ple, badness may for a long time mean, among other things, disobedience. There comes a time, however, when possibly dis- obedience seems in some crisis the only alternative to lying. We have also identified lying with badness. What shall we do ? Well, whatever we do, we have at least laid the founda- tion for the reconstructive development of our concept of badness, by noting that disobedience may sometimes be neces- sary to the attainment of the maximal possible good. We Tiecessarily make judgments about badness in such a case, and the transformation, whether shrinkage or enlargement, which the concept undergoes, is a direct expression of the effect of judgment. The development as well as the origin of such concepts is, accordingly, most intimately bound up with the judging operation. JUDGMENT; ELEMENTS OF REASONING 27,^ Before generalising upon this single case, it would, of course, be desirable to examine every variety of concept in order to see if any of them originate independently of such judgments. This is, however, evidently impracticable, and we shall have to fall back upon the consideration that inas- much as the concept is always a mental recognition, or desig- nation, of specific meaning, there must, in the nature of the case, sooner or later be a judging process involved in it; for judgment is neither more nor less than the overt recognition and expression of just such relations as are embodied in the concept. We must not forget, however, that our common every-day concepts are often formed under the pressure of practical experience with little or no conscious reflection, and by means of the most rudimentary and implicit types of judg- ment. Order of Development of the Cognitive Processes. — This analysis inevitably raises the question as to what is the most primitive and fundamental mode of conscious operation to which we have thus far given attention. We have shown that the conceptual element is present in perception, and we had already explained that in a genetic sense perception evidently antedates memory and imagination. Now we seem to find judgment as a precursor of the concept. What is the real order of development among these activities? To secure a correct impression regarding the genetic rela- tions among these processes, we must resort to an analogy which we have employed on a number of previous occasions. The development of an organism of any kind is accomplished by means of the gradual unfolding of structures, and the gradual evolution of functions, out of undifferentiated matrices. The fertilised ovum contains in a way, implicit within itself, all the potentialities of the fully developed organism which may subsequently grow out of it. But no inspection which we could make of the ovum would enable us to detect these invisible members. Step by step the homo- 274 PSYCHOLOGY geneity of the ovum gives way to more and more complex conditions, until finally the process of assimilation and dif- ferentiation issues in the full-grown organism. At each step in the progress toward maturity the several anatomical organs and the various physiological functions are moving together toward completion. At one stage one group of these ele- ments may seem further advanced than others, but there is nevertheless mutual dependence of each factor upon every other, and each member of the several groups is from the beginning represented by some forerunner, however crude. So it is with the psychical operations which we have been studying. Judgment, conception, memory, imagination, per- ception, and still other processes, which we have not as yet examined, appear in consciousness in crude embryonic form from the very first ; and each process, which we have described and analysed under one or another of these names, in its de- veloped condition really involves each of the other processes. At certain moments consciousness presents itself as domi- nantly engaged in the way we call perception, sometimes in the way we call imagination. But each operation involves tbe other, and it would hardly be possible to point to a stage in development where one was obviously present and the other obviously and altogether absent. Judging is in a precisely similar situation as regards its primary or secondary nature, its early or late appearance, in the history of the individual consciousness. We m.aj, per- haps, make this point clear most easily by examining the case of perception which we have seen to be present past all rea- sonable question from the earliest moments of waking life. When we perceive a familiar object, say a chair, the mental operation of cognising the object is essentially equivalent to the assertion, "this is a chair," or "this is a thing to sit upon." True, we rarely put the conclusion in this explicit form to ourselves, ISTevertheless, the mental process is prac- tically akin to the proposition, and in our first intelligent judgment; elements of reasoning 275 application of names to objects it is exactly of this character. Indeed, the first childish exclamations, which represent in however amorphous a fashion the precursors of language, are of this type. The whole mass of feelings which such early infantile vocalisation may serve to indicate is often extremely complex and extended. One sound may designate an expe- rience, which as adults we should describe as "this-is-the- sound-of -the-coming-to-take-me-up-and-f eed-mo - which - is - a - delightful-experience." Another sound may represent judg- ments in the form of a command, such as '^I-am-hot-and I-wish-you-would-take-the-blanket-off." Let it not be supposed that we mean to credit the half- inarticulate infant with the mental recognition of all the dif- ferentiated elements in these cases to which we as adults are sensitive. Quite the contrary. It seems probable, as we saw, when we discussed attention and discrimination, that the early experiences of the baby are extremely vague, not in the sense of being positively confused, as adults sometimes are when embarrassed, but in the negative sense, in Avhich vagueness means absence of distinct, well-recognized mental control. These primitive judgments are rudimentary expres- sions of just such reactions upon those indefinite, undifferen- tiated features of infant consciousness as we find appearing in ourselves when we make judgments about our more highly elaborated and more definitely discriminated ideas. The earliest rudimentary processes of judgment consequently in- volve the manipulation of unanalysed masses of experience, which we subsequently discover, through processes of disso- ciation, comparison, and judgment, to be extremely complex. It is quite possible, as has been already suggested, that the impersonal judgments, such as '^it thunders," represent sur- vivals of assertions of just this primitive kind about total experiences whose elements are only vaguely and imperfectly analysed. Judgment as the Primitive Cognitive Activity. — It seems 276 PSYCHOLOGY highly probable from the foregoing that in its original form all judgment is essentially a reaction upon immediately pres- ent perceptual experiences. Undoubtedly, rude judgments in which memory and imagination play leading roles may occur at a very early period. But it seems quite certain that their most important functions must come somewhat later than the periods during which perceptual judgments are first clearly in evidence. Moreover, inasmuch as these rudimentary forms of judgment appear to involve as their most characteristic fea- tures, like the highly developed ideational judgments, the recognition, or assertion, of relations, it seems impossible to deny that the simplest case of perception, with its connec- tion of a sensory stimulation with something already fami- liar, is also implicitly, at least, of the same genus as the judg- ment. When we ask, then, which of the several mental processes we have described is most fundamental, we must reply that if the question applies to the order of appearance in conscious- ness after the hypothetical first sensation, no single one enjoys this preeminence. They develop together, and are all, in one way or another, present from the oiitset of conscious life. In- deed, they owe their separateness chiefly to our analysis and not to any natural isolation from one another. If the ques- tion means, however, Avhich of the processes, as we have dis- tinguished them, exhibits most conspicuously the whole scope of cognitive conscious capacities, then we must probably reply, judgment; because in this activity the detection and manipu- lation of relations is possibly most obvious, and this undoubt- edly is the great mental achievement in the building up of knowledge and the controlling of conduct, to which ultimately all these processes revert for their final significance. In this sense, therefore, judgment is the most fundamental operation of consciousness on the cognitive side. Judgment a Process of Ordering and Organizing Mental material. — Before leaving this account of judgment and pass- JUDGMENT; ELEMENTS OF REASONING 277 ing on to consider reasoning, a further word should be said of the fact which came to our notice a moment ago in speaking of the judging process in the primitive consciousness of infant life. Judgment undoubtedly begins with a process of disentangling the various constituents of some large and rela- tively vague experience. The operation which we described in an earlier chapter ias discrimination is commonly identical with these rudimentary judging processes. jSTow in so far as judgment does really deal in this way with the analysis of ideational (or perceptual) experiences, which are to start with undifferentiated wholes, it would seem to be necessary to regard it as a process in which relatively vague ideas are resolved into their definite constituents, rather than as a pro- cess in which already distinct and separate ideas are brought together. It will be remembered that our previous descrip- tion of it is more closely allied to the second of these views about it. As a matter of fact both views are correct in the conception which they emphasise, and the disparity between them is only apparent. Just as we saw was the case in the differentiation of the various sensations out of the relatively homogeneous con- scious continuum with which life probably begins, so the materials upon which our judgments are based and with which they deal are all necessarily elements of our own per- sonal experience. So far as we predicate anything of an object, — for example, "iron is a metal," — it may be said that we have simply dissected the idea of iron (our concept), which was already present to our minds, instead of adding to it some neiv idea, i. e., metal. Taken literally, this is a true statement of the facts. It is only false by virtue of that which it fails to add. The concept of iron is a concept dis- tinguished from that of metal. We not only may bring these two concepts together mentally, but we frequently do unite just such concepts in the form of judgments, which are prac- tically valuable to us in enabling us to emphasise such phases 278 PSYCHOLOGY of our thoughts as are momentarily important for us. Judg- ment is, then, in its most explicit forms, undoubtedly a pro- cess in which we synthesise concepts in the course of noting and asserting relations. Yet the concepts which we thus unite are with equal certainty already elements of our stock of knowledge, and so we may seem to have made no gain by the judgment, much less to have added a new idea to some old idea. But the gain is often very real, because the synthesis may bring out relations of which previously we were not clearly cognisant. From this point of view judgment is not so much a matter of creating wholly new mental material as it is a matter of ordering and organizing our mental equip/- ment in the most efficient possible manner. CHAPTER XII THE FORMS AND FUNCTIONS OF REASONING Judgment and Heasoning. — From tlie illustration with which we set out in the last chapter in our first rough analysis of reasoning, we observed that the solution of the problem with which we were hypothetically engaged involved a series of judgments. We therefore turned aside to examine more closely into the nature of judgment; and we have discovered that this is an analytic-synthetic process, in which concepts are employed and elaborated. As the great majority of our important concepts have a linguistic basis, it goes without saying that reasoning makes almost constant use of language. It now remains to survey somewhat more fully the manner in which our judgments are combined to form the various types of reasoning. We proposed as a somewhat provisional defini- tion of reasoning, at the beginning of the last chapter, the phrase "purposive thinking," meaning by this to designate any thought process in which we were thinking toward some end, attempting to overcome some difficulty, or solve some problem. If we turn to certain familiar instances of this sort of thing in every-day life, we shall at once obtain an impres- sion of the fashion in which we make use of our judging ac- tivities. Practical Reasoning. — Suppose that we are about to make a long journey which necessitates a choice from among a num- ber of possible routes. This is a case of the genuinely prob- lematic kind. It requires reflection, a weighing of pros and cons, and the giving of a final decision in favour of one or another of the several alternatives. In such a case the 28o PSYCHOLOGY procedure of most of us is after this order. We think of one route as being picturesque and wholly novel, but also as being expensive. We think of another as less interesting, but also as less expensive. A third is, we discover, the most expedi- tious, but also the most costly of the three. We find ourselves confronted, then, with the necessity of choosing with regard to the relative merits of cheapness, beauty, and speed. We proceed to consider these points in the light of all our inter- ests, and the decision more or less makes itself. We find, for instance, that we must, under the circumstances, select the cheapest route. Now, this process is evidently made up of a number of judgments, in which we have employed various conceptions of the routes and the consequences connected with their choice. Obviously, also, we have made constant use of the machinery of association by means of which the various connected ideas have called one another into the mind. Our conclusion is seemingly the outcome of a series of judgments, whose num- ber may be wholly indeterminate, and whose order is far from systematic. Nevertheless, the process results in a solution of the problem, the conclusion is essentially a reasoned one, and the operation is altogether typical of the fashion in which we actually deal with the practical problems of common ex- perience. T\Tien we look at the successive steps a little more closely, we see that such judgments bring into the foreground some aspect of the general prohlem which assists us in viewing the situation in its entirety. Thus, the idea of cost as less by one route than by the others proved in our final estimate to be of fundamental significance. But we could not isolate this element of the problem and conceive it aright until we had compared routes with one another, and considered all the expenses involved in each. Only then were we in a posi- tion to assert which route was cheapest. This crucial judg- ment issued immediately from our comparison of the several FORMS AND FUNCTIONS OF REASONING 281 routes with one another, but the process of comparison was itself an indispensable step in reaching our final choice. We considered speed in a similar manner, and found that all the routes were satisfactory enough in this particular. Finally, the consideration of beauty and the pleasure of the journey is canvassed in like manner, and we find from the ideas which come into our minds that one route is markedly preferable. This factor of beauty remains, then, to settle accounts with the item of economy. The ultimate decision involves our taking stock of our financial status, past, present, and future, and the issue is settled on the basis of the story told by this set of facts. Each step in the process has been relatively simple, and entirely intelligible. We have allowed certain ideas, which we have abstracted in our mode of con- ceiving the problem, to take up by association other ideas re- lated to them in ways which bear upon the case in hand ; and from the judgments which we pass upon the meanings of these ideas our choice is made and our volition determined. Our effectiveness as practical reasoners (or theoretical reasoners, either, for that matter) will depend then, first, upon the skill with which we succeed in conceiving the problem correctly, and second, upon the speed and accuracy with which this con- ception suggests to our reasoning processes the recall of the special ideas appropriate to the case at hand. The whole series of judgments employed could finally be reduced to two or three (or possibly to one), which, as the outcome of our tentative weighing of now this claim and now that, have proved to be finally significant. In a sense the judgments have all been connected and related. They have all arisen in response to our persistent dwelling upon the problem before us. But a few of them depend upon one another in an even more intimate way, and these are the per- manently significant ones. For example: "Two routes cost more than $1000; I cannot afford to pay more than $800; I must therefore patronize the third route." 282 , PSYCHOLOGY Value of Association by Similarity. — In so far as reasoning involves associative processes, it is clear that association by similarity will be of highest importance, especially in the more abstruse forms of thinking. The more complex types of problem with which we have to cope often require for their successful solution the application of facts and principles which have no connection with the matter in hand, save some fragile bond of similarity. The detection of these delicate links of relation is an achievement which characterises in high degree only the most remarkable minds, the geniuses. The rest of us find, to be sure, that we outstrip the brutes enor- mously in our capacity to employ this form of associative nexus. But the great revolutionary achievements in human reason have to wait upon the man and the hour, and when they are compassed, they generally reveal a marvellous mani- festation of the capacity for discerning similarity. Newton's formulation of the law of gravity may serve to illustrate the point. Eeasoning- and the Syllogism.— Now, to many persons the process of selecting a route for a journey will seem a mislead- ing illustration of reasoning, because it will not appear to be sufficiently abstruse, nor sufficiently orderly and inevitable. It will represent what they may prefer to call "practical reasoning," as we have done, although we have not meant by the use of the term to deny to the process the essential char- acter of reasoning. We shall be told that when we really reason we perform such mental deeds as the following syllo- gism exhibits: All men are mortal; Socrates is a man. Therefore Socrates is mortal. Here we are assured we have new facts attained by reason ; here is perfect order and symmetry, instead of miscellaneous groping for correct conclusions, which may, or may not, be FORMS AND FUNCTIONS OF REASONING 283 attained J here are judgments arrayed in serried ranks, each supported by its neighbour, and the final judgment an irre- futable consequence of its companions, from which our think- ing set out. In response to this suggestion we have only to inquire whether or no our original thinking really goes on in this way, or whether this example illustrates the arrangement of which certain of our thought processes are susceptible after they have been pruned of excrescences. Our own view about this question is doubtless indicated by the mode in which we have approached it. There can be no doubt that the cele- brated syllogism which we have just proposed reveals an extremely fundamental fact about the relations of certain of our judgments to one another. That the syllogism also repre- sents the actual mode in which we commonly reach (Conclu- sions is altogether another proposition, and to one which assent certainly cannot be given. The question here at issue is purely one of fact, and each one must determine for himself whether in his reasoning processes he finds himself proceed- ing in the syllogistic manner. When we examine our thinking, with this question in mind, most of us find that neither as regards the order of the several steps, nor as regards their number, does our com- mon reasoning comply wth the pattern of syllogism. In instances like that of our illustration we should rarely have any recourse to the second proposition, or the minor premise, as logicans call it, even provided we found it necessary to consider the truth of the conclusion. Moreover, it would as a rule be only in case we found it necessary to verify the truth of the concluding proposition that we should revert to either of the other propositions; and then the order of our thought would be — first, the conclusion; second, the major premise. So that neither the order nor the number of judg- ments corresponds to the syllogism with which we started. As a device for exhibiting the source of our confidence in 284 PSYCHOLOGY the truth of the conclusion, the syllogism undoubtedly pos- sesses a value; for it makes explicit and clear in the fewest possible words the fundamentally important relations among the ideas involved. It is, however, as a method of exposition, demonstration, and proof, rather than as a type of actual constructive thinking, that it gets its chief significance. Nev- ertheless, it possesses one characteristic which is peculiar to many reflective processes, and to this we must briefly refer. Deduction.— The major premise — "All men are mortal" — contains an assertion of a general principle which we have observed that we may use as a principle of verification for such an assertion as that of the conclusion — "Socrates is mortal." Now, general principles play essentially the same role in our thinking as do the general ideas which we dis- cussed in the chapter on conception. They summarise, just as concepts do, large masses of human experience, and in our purposive thinking we repeatedly have occasion to employ them. We might call them complex concepts. These general principles represent the counterparts In our conscious operations of the principle of habit in our motor coordinations. Just in so far as we regard them as really stable and well established, we use them almost reflexly in our thinking, and apply them without more ado to the deter- mination of conclusions about such facts as they may con- cern. Thus, having assured ourselves that a certain act is really stealing, we instantly class it as despicable and wrong; having learned that a substance of peculiar appearance is wood, we are immediately prepared to find that it will burn; if we hear of the discovery of a new planet, we assume without question that it will possess an elliptical orbit. These reac- tions consist in applying to appropriate things the habitual accompaniments of specific objects, or events, in the form of general ideas, or principles, concerning similar objects and events. Such a process lends perspective to the special sub- ject to which the principle is applied, by bringing it into FORMS AND FUNCTIONS OF REASONING 285 overt connection with the experience to which it may be most immediately germane, while it enriches and fortifies the gen- eral principle itself by adding to its scope a new and definite instance. It demands no argument, beyond the mention of the facts just described, to demonstrate that we make a con- stant use of general principles in some such fashion as this. The problem is at once suggested by the foregoing discus- sion of deduction, as to how we obtain the general principles therein at issue. This brings us to the complementary proc- ess which logicians designate induction. Induction. — According to the familiar accounts of it, induc- tion is the operation by means of which we come to generalise upon individual events. For example, having observed num- bers of specific instances of the phenomenon, we come to the conclusion that all paper is combustible. In a similar way we come to assert that all mammals have lungs, that masses attract one another, etc., etc. Criticism of Induction. — Now, logicians have argued at great length upon the question whether we really succeed by inductive inference in going beyond the particular facts which have actually been examined. They have also consid- ered at great length the criterion, or warrant, upon which inductive principles proceed, supposing that they ever do transcend the facts from which they set out. Sometimes it has been maintained, for example, that the inductive general- isation, "All men are mortal," which is based upon our examination of a finite number of cases of human mortality, obtains its ultimate significance for knowledge simply by virtue of the assumed uniformity of nature. What has hap- pened a number of times will always happen under like con- ditions, is the meaning of this view. Or, stated more rigidly, whatever has happened under given conditions will always happen under the same conditions. On this basis a single occurrence of a phenomenon, if thoroughly understood, would justify a generalisation about all other instances of the 286 PSYCHOLOGY phenomGnon. Many othei" views of the matter have been defended, but we can hardly enter upon them. Suffice it for our purposes to observe that whatever may be the final merit and reliability of inductive inferences, we do in our actual thinking make constant use of such generalisations, and on the whole with practical success. Indeed, after our account of habit and association and our account of the formation and development of concepts, we should be ill-prepared for any other conclusion. Having found a certain characteristic common to a large number of events, it could not well be otherwise than that we should be predisposed by the principle of habit to connect this character with all other events which we Judged to be of like kind. This would tend to occur on the level of mere trains of associative ideas, as in revery, where it might, however, often escape attention ; it would also come out clearly in the recognition of points in common among such occurrences as we found our- selves obliged to reason about in the course of overcoming difficulties, whether practical or theoretical. Thus in revery our thoughts might run upon the planets, and as the ideas of them passed through our minds we should probably think of them all as spherical, and yet this common property might escape our definite notice. In reasoning, however, we should often find it indispensable to emphasise common qualities of this kind. So, for instance, in attempting to predict weather conditions we should speedily find it necessary to proceed on the generalisation that all low barometric phenomona were indicative of storm formation. The same exigencies, there- fore, which lead us to form general ideas, also lead us to that special type of idea which we more often call a general prin- ciple and express in a proposition. It may be added that undisciplined minds, following a tendency natural to us all, constantly generalize on single events which are imperfectly understood and consequently fall into persistent error. The fallacy consists, however, not FORMS AND FUNCTIONS OF REASONING 287 SO much in generalising on one event as in generalising on an event which is not correctly or fully apprehended. Deduction and Induction Compared.— In comparing deduc- tion and induction it is often said that induction necessarily precedes deduction, because we obviously cannot apply our general principles until we possess them, and it is by means of induction that we obtain them. It is also said that in deduc- tion our thought proceeds from the more general to the less general, from the universal to the particular; whereas in in- duction the order of procedure is reversed. There is an ele- ment of truth in both assertions, but this form of expressing it is certainly misleading. The truth in the first contention consists in the fact that all general principles are based upon particular experiences. But this does not mean that inductive processes occur first, and then at a later step deduction appears. Both kinds of process go on together, as we shall see in a moment. Indeed, strictly speaking, they are in the last analysis simply two phases of one and the same process. The truth in the second assertion resides in tbe fact that some portions of our think- ing proceed under relatively more habitual forms than others. The deductive process represents the application of a mental habit, or principle, to a practical case, under just such condi- tions as we have already described. The inductive process represents more distinctly the formation of these halits of thought. In both cases, however, so far as concerns the prog- ress of the successive thoughts, we always find that the advance is from particular to particular. Moreover, the advance is not so much an advance from the particular idea X to the independent and particular y, now shown to be related in some way to x, as it is a development of the idea X, hitherto undifferentiated in this special fashion, into the idea x containing a y relation. Thus, the generalisation about low barometric conditions and storm formation is not a mental process in which two wholly disconnected ideas are 288 PSYCHOLOGY brought together. It is simply a process in which the hith- erto unspecified experience "low-barometer-storm-forma- tion^' is resolved into its fuller significance for practical use. Similarly, in subsequent deductive operations with this prin- ciple, i. e., all low barometric conditions indicate storms imminent, we proceed from the particular idea "low barome- ter,^^ to the particular idea "storm forming." However con- venient, therefore, it may at times prove to speak of passing from the general to the particular, and vice versa, we must remember that in our actual thought processes we always juxtapose particulars; or more precisely, we deal with dis- criminable features of a single mental particular. Of course it will be understood from our study of the development of concepts that these particulars are under this treatment modified incessantly, both by expansion and contraction. Habit and Adaptation in Deduction and Induction.— We have seen from time to time throughout our work that each mental process which we have examined contains some old features and some new features, that it reflects the prin- ciple of habit and the principle of fresh adjustment to novel conditions. Induction and deduction are further illustra- tions of this same fact. Just as in perception we observed the new element in the sensory stimulus, and the old element in the reaction by a modified cortex, so we have seen that' induction represents that function of our purposive thinking in which the new adjustment is uppermost; whereas deduc- tion represents more conspicuously the application of ac- quired habits. If the parallel is really genuine, we should expect to find, as we have at each, previous step, that the two attributes of novelty and familiarity in the elements employed are never entirely dissevered from one another, and so we should expect to find substantial warrant for our remark a few lines above, that induction and deduction are but phases of a common process. That they are actually conjoined in this way does not mean that they always are met with in a FORMS AND FUNCTIONS OF REASONING 289 condition of perfect balance. It may much more naturally be expected that sometimes one and sometimes the other will present itself as more immediately important and more properly conspicuous. We have seen an analogous case in the instance of memory when compared with some kinds of per- ception. In the one case the obvious emphasis falls upon the new, in the other upon the old. So it is in reality with the relation between deduction and induction. In reaching the induction, "all low barometerr=storm formation,^' we may suppose a number of instances to have been examined before the generalisation is made. Now, the intelligent apprehension of the terms concerned in the judg- ments, that is, low barometer and storms, evidently involves a reference back to past experience, to past factors of knowl- edge, which is, as we have seen, the essential feature of deduc- tion. Moreover, the actual procedure by which we assure ourselves of the tenability of such an induction consists in comparing mentally each new instance with previous similar instances. In this operation the old experiences practically occupy the place of general principles, under which we array the new case. So that the deductive characteristics are evi- dently present in an unmistakable way in inductive forms of reasoning. Conversely, when we apply a general principle, or infer that a special consequence will follow an event, because of the general class to which it belongs, we inevitably avail ourselves of inductive methods, in so far as we label the new fact. When we predict a storm because we observe a fall in the barometer we are in reality dealing with a new specific instance, which we generalise in an essentially inductive way. We may call it a case of deduction, because we have already convinced ourselves of the invariability of the' connection between the storm phenomena and the particular barometric conditions. ISTevertheless, the actual mental pr