;?tf;;. 
 
 a.> :.'. 
 
Class _ 
 Book — 
 Copyright N". 
 
 ^ri 
 
 COEOaCHT DEPOStr. 
 
A SYSTEM 
 OF PSYCHOLOGY 
 
A SYSTEM 
 OF PSYCHOLOGY 
 
 BY 
 
 KNIGHT DUNLAP 
 
 ASSOCIATE PROFESSOR OF PSYCHOLOGY IN THE 
 JOHNS HOPKINS UNIVERSITY 
 
 NEW YORK 
 
 CHARLES SCRIBNER'S SONS 
 
 1912 
 

 Copyright, 1912, by 
 CHARLES SCRIBNER'S SONS 
 
 eCI.A309474 
 
 / 
 
TO 
 
 ELMER ELLSWORTH BROWN 
 
 IN ACKNOWLEDGMENT OP WHAT I OWE TO HIS 
 TEACHING AND FRIENDSHIP 
 
PREFACE 
 
 I SHOULD not be willing to add to the large num- 
 ber of psychology texts already in existence did I 
 not believe that this book, in spite of its faults of 
 omission and commission, possesses certain good 
 points not found in the other English texts of re- 
 cent date. 
 
 My greatest effort has been to present as consist- 
 ent and systematic a sketch as possible of the general 
 field of normal human psychology, elaborating the 
 details only when they are essential to the general 
 survey. In a field which is in great and increasing 
 danger of becoming unsystematized to the point of 
 chaos, even to the trained specialist, this method 
 of introduction is absolutely essential. 
 
 I have tried to show that the data of psychology 
 cannot at present be definitely described except in 
 terms of theories which are more or less ^^philosoph- 
 ical,^^ and that the attempt to divorce the data from 
 the theories would result in the uncritical acceptance 
 of fragments of theories. It is important that the 
 student should grasp this truth in the beginning, 
 
Vlll PREFACE 
 
 and not be taught a pseudo-final system of facts 
 which later must crumble cataclysmically when he 
 takes a new point of view. 
 
 I have not attempted to write a book so simple 
 that the student might read and understand it 
 without effort: rather, I have endeavored to write 
 that which should demand and reward hard study. 
 The book is not designed to be made the sole basis 
 of a course in elementary psychology. It ought to 
 be accompanied by lectures prepared by a com- 
 petent teacher, having special reference to the 
 difficulties and lacunae of the text, and to its dif- 
 ferences from the psychological theories held by 
 the teacher. Certainly, the book cannot be used as 
 a text from which both students and teacher may 
 draw their information. As a main or supplement- 
 ary text for semiadvanced students, it should find 
 its greatest usefulness. 
 
 The only originality I can claim is in the way in 
 which I have worked up materials borrowed from 
 many places. I have not given credit for my bor- 
 rowings, because in many cases the sources are too 
 obvious to be mentioned, and in other cases what 
 has been borrowed has been so distorted in the proc- 
 ess that the individual to whom I am indebted 
 might resent the ascription if credit were given. 
 
PREFACE IX 
 
 The chief influences which have shaped my psy- 
 chological constructions have come from the writ- 
 ings of James and from my contact, as a pupil, first 
 with Howison, later with Stratton, and finally with 
 Miinsterberg. 
 
CONTENTS 
 
 CHAPTER PAGE 
 
 I. Introduction: 
 
 1. The Meaning of Psychology .... 1 
 
 2. Terminology 5 
 
 3. Extrinsic Helps 8 
 
 II. Preliminary Analysis of Content: 
 
 1. Complexity of Content and Complexity 
 
 of Experience 12 
 
 2. General Classification of Elements of 
 
 Content 13 
 
 3. Terminology 16 
 
 III. Sensation in General: 
 
 1. Sensation, Physical Stimulus, and Physi- 
 
 ological Process 18 
 
 2. Matter and Psycho-Physical Causation . 25 
 
 3. The Lag of Sensation 27 
 
 4. Secondary Sensations 31 
 
 5. The Characters of Sensation .... 32 
 
 IV. Sensation-Quality : 
 
 1. General Classification 38 
 
 2. Sensation and Brain Process .... 43 
 
 3. Sensations of Taste ....... 44 
 
 4. Sensations of Smell 49 
 
 5. Visual Sensations 54 
 
 6. The Schematic Representation of Visual 
 
 Qualities 56 
 
 7. Achromopsia and Parachromopsia . . 67 
 
 8. Color Adaptation and Contrast ... 74 
 
 9. Auditory Sensations 80 
 
 10. Cutaneous and Subcutaneous Sensations 84 
 
 11. Kinsesthetic and Coensesthetic Sensations 95 
 
 xi 
 
Xll CONTENTS 
 
 CHAPTER PAGE 
 
 V. Thresholds of Consciousness .... 
 
 1. Stimulus-Thresholds 101 
 
 2. Stimulus Difference Thresholds . . . 105 
 
 3. Other Thresholds 106 
 
 4. The Constant Error 106 
 
 VI. Sensation-Intensity: 
 
 1. Intensity of Sensation and Intensity of 
 
 Stimulus 109 
 
 2. Weber's LaW Ill 
 
 3. The Comparison of Intensity-Differences 114 
 
 4. The Relativity of Sensation .... 116 
 
 5. Beats 118 
 
 VII. Protensity and Extensity of Sensation: 
 
 1. The Duration-Quality 120 
 
 2. Extensity 122 
 
 3. Overtones and the Musical Scale . . . 125 
 
 4. Timbre 132 
 
 5. Extensity and Intensity 134 
 
 VIII. Local Significance: 
 
 1. Localization and Local Sign . . . . 137 
 
 2. The Discrimination of Local-Sign Differ- 
 
 ences . 139 
 
 3. Local Sign in Auditory Sensation. . . 143 
 
 4. Olfactory Local Sign 145 
 
 IX. Relational Elements in the Content of 
 Consciousness: 
 
 1. General 146 
 
 2. Platonic Ideas and Matter 149 
 
 3. Intellect 150 
 
 4. The Reality of Relational Content . . 151 
 
 X. Images as Elements of Content: 
 
 1. Imagination and "Image Types". . . 153 
 
 2. The Function of Imagination .... 160 
 
CONTENTS Xlll 
 
 CHAPTER PAGE 
 
 XI. Retention, Memory, and Recall: 
 
 1. Retention 169 
 
 2. Memory 174 
 
 3. Recall 177 
 
 XII. Association: 
 
 1. The Principles of Association .... 180 
 
 2. Voluntary Recall 192 
 
 3. The Probable Physiological Basis of 
 
 Association 194 
 
 XIII. Perception: 
 
 1. The General Nature of the Content in 
 
 Perception 196 
 
 2. Perception, Illusion, and Hallucination . 201 
 
 3. The Determination of Perceptual Truth 
 
 and Falsity 205 
 
 4. The Causes of Illusion 208 
 
 5. Space Perception 212 
 
 6. The Perception of Things 227 
 
 7. The Perception of Time 229 
 
 XIV. Affective Content, or Feeling: 
 
 1. Affection and Cognition ...... 242 
 
 2. Pleasure and Pain 244 
 
 3. Conation and Interest 250 
 
 4. Emotion 255 
 
 5. The Ccensesthetic Factor in Emotion . . 259 
 
 6. The Cognitive Factor in Emotion . . 261 
 
 7. The Classification of the Emotions . . 263 
 
 XV. Action and Will: 
 
 1. Action in General 265 
 
 2. Volition 270 
 
 3. Volition as Activity 273 
 
 4. Automatic Action 274 
 
 5. Instinctive Action and Learning . . . 277 
 
 6. Habit 281 
 
XIV 
 
 CONTENTS 
 
 CHAPTER PAGE 
 
 XVI. The Self, or Empirical Ego 285 
 
 XVII. The Degrees of Consciousness: 
 
 1. Consciousness, Attention, and Vividness . 292 
 
 2. Vividness and Intensity 295 
 
 3. Factors Determining Vividness . . . 298 
 
 4. Attention and Interest 301 
 
 5. Vividness and Practical Advantage . . 302 
 
 6. Judgment 303 
 
 7. The Scope of Attention 304 
 
 XVIII. The Time Relations of Consciousness: 
 
 1. Presentation and Image 306 
 
 2. Rhythm 309 
 
 3. Duration of Attention to Continuously 
 
 Presented Sensation 313 
 
 4. The Fluctuations of Minimal Sensations 316 
 
 5. The Selective Fluctuation of Vividness . 318 
 
 6. The Conditions of Constant Attention . 323 
 
 XIX. The Subconscious: 
 
 1. The Lower Limit of Vividness . . . 325 
 
 2. What the Subconscious is Not .... 326 
 
 3. The Two Sorts of Marginal Consciousness 328 
 
 4. Multiple Personality 331 
 
 XX. The Ego 336 
 
 XXL The Occult: 
 
 1. The Study of the Occult 342 
 
 2. Telepathy 343 
 
 3. Mysticism 348 
 
 4. Spiritualism and Mediumship .... 350 
 
 References . .' 355 
 
 Index 363 
 
A SYSTEM 
 OF PSYCHOLOGY 
 
A SYSTEM 
 OF PSYCHOLOGY 
 
 CHAPTER I 
 
 INTRODUCTION 
 I. The Meaning of Psychology 
 
 It is much easier to tell the beginner what psy- 
 chology is not than it is to tell him what psychology 
 is. Just as it would be impossible to give an in- 
 teUigible definition of mathematics to a person un- 
 familiar with the elementary principles of number- 
 relations, so it is impossible to make clear to the 
 average student the nature of psychology when he 
 is just beginning to study it. In order that one 
 may have a definite idea of what psychology is, he 
 must know some psychology; and a person who 
 has not studied the subject under competent guid- 
 ance is not apt to know any psychology in the strict 
 sense. It is true, on the one hand, that there is a 
 great deal of information which is popularly called 
 psychological; and, on the other hand, that every 
 
2 A SYSTEM OF PSYCHOLOGY 
 
 person knows much that is really psychology, al- 
 though the persons in question do not realize that 
 it is such. These two species of misunderstanding 
 contribute to the difficulty of the task when one 
 commences to study the subject scientifically. It 
 is clear, therefore, that what we say now in a general 
 way concerning psychology should be brief, and 
 that the meaning thereof will probably be clear to 
 the student only as he reverts to it after completing 
 the volume. 
 
 We may commence advantageously by warning 
 the student against some of the more common 
 misconceptions of psychology. In the first place, 
 while on the one hand psychology is not the " study 
 of the soul,'' on the other hand it is not "soulless'' 
 in the sense of doing away with a soul. It is a com- 
 monplace that \jrvxo\oy{a is not to be taken in its 
 literal significance as the name of our field of labor, 
 and that a considerable portion of the psychologi- 
 cal discussion gets along without any mention 
 of any sort of "soul." But in a comprehensive 
 analysis it is not possible to avoid reference to 
 something which may properly be called a "soul," 
 although it is by no means the "psyche" of the 
 Greeks and of the current popular conception, and 
 although it is impossible really to study it. 
 
INTRODUCTION 6 
 
 In the second place, psychology deals very little 
 with the so-called "occult"; with telepathy, clair- 
 voyance, and the other charlatanisms which are 
 often so successfully employed in separating the 
 fool from his money. Yet if we do not affirm, 
 neither do we deny, that there may be, at the core 
 of some of these concretions of humbuggery, cer- 
 tain elements of psychological interest and impor- 
 tance. The investigation of such matters belongs, 
 however, not properly to psychology, but to ^'psy- 
 chic research." ^ 
 
 In the third place, the term "psychological" in 
 current popular usage designates a certain delicacy 
 or niceness of discrimination or adjustment. Thus 
 the "psychological moment" implies an instant of 
 time so appropriate for a certain act that a moment 
 before would be too early, and a moment after too 
 late. Any very precise analysis or description, 
 of the characteristics and activities of human be- 
 ings; or even a simulation of precision, is called 
 "psychological"; and hence we find mention of 
 "psychological" novels, and so forth. Now while 
 psychology modestly acknowledges the pretension to 
 
 ^The terms "psychic'^ and "psychical" must be distin- 
 guished carefully from "psychological." It is to be regretted 
 that either of the first two terms is ever applied to the data 
 which we study in the name of psychology. 
 
4 A SYSTEM OF PSYCHOLOGY 
 
 exactness of analysis, she must deny any exclusive 
 claim thereto, and cannot even pose as the only 
 science which analyzes human activity and ex- 
 perience. In this popular sense of the term, physi- 
 ology, logic, and ethics are, if anything, more " psy- 
 chological'' than is psychology. 
 
 Finally, psychology is not the study of the func- 
 tions of the nervous system. In fact, all the essen- 
 tial points of psychology can be expounded, as they 
 have been developed, without reference to the ner- 
 vous system, or by reference to a conception thereof 
 which is ridiculously inaccurate. Nevertheless, it 
 is true that psychological principles and facts are 
 more easily described and investigated when re- 
 ferred to the structure and probable activity of the 
 brain and nerves, as understood by the person to 
 whom described or by whom investigated, and we 
 believe that the more closely the physiological con- 
 ceptions approach agreement with the actual facts of 
 structure and function, the more facile the progress 
 of psychology. 
 
 As for a positive definition we may give the fol- 
 lowing, which will be made clear by the further 
 discussion: psychology is the study of experience; 
 of the reference of experience to its content; of any 
 direct reference which it may have to a subject of 
 
INTRODUCTION O 
 
 experience; and of the content of experience in so 
 far as it is directly related to experience. 
 
 2. Terminology 
 
 The terms used in this book may at first be 
 a series of stumbling-blocks. Not only will the 
 meaning in which many of them are used be found 
 to differ decidedly from the meaning attached to 
 them in every-day language, but in many cases the 
 terms are not used in the senses in which thev are 
 used in other books which will be read by the stu- 
 dent. This confusion is unavoidable. The terms 
 have been used in so many different sciences (to say 
 nothing of their unscientific uses), that they have 
 acquired a variety of meanings, and we are obliged 
 to select the significations which seem most appro- 
 priate. Some words, such as "mind,^' "intelli- 
 gence," and "soul," have had, and still have, so 
 many different meanings that they have come at last 
 to mean practically nothing, and we hesitate to use 
 them at all where accuracv is essential. In the 
 choice of the signification to be given to a term we 
 should be guided not only by predominance of 
 present usage amongst psychologists, but also 
 by the historical setting of words, and by popular 
 usage; and having attached a given signification to 
 
6 A SYSTEM OF PSYCHOLOGY 
 
 a term we ought to endeavor to adhere to it through- 
 out. 
 
 The term ^* experienced^ is currently used in two 
 ways. In the first place, it means to know, appre- 
 hend, or perceive something; as when I say I ex- 
 perience a sound, a color, a pain, or an emotion. 
 In the second place, it means that which is appre- 
 hended or directly known, that is, the sound which 
 is heard, the emotion which is felt, etc., are called 
 experiences, or kinds of experience. There has 
 been a great deal of shifting back and forth from the 
 one of these meanings to the other, which has in- 
 troduced deplorable confusion; and, manifestly, if 
 we wish to avoid such trouble we must adopt and 
 cling to one meaning. We shall, therefore, use the 
 term in the first sense given above; to designate the 
 being aware of something, and not that of which 
 one is aware (except in so far as one may possibly 
 be aware of being aware, which need not concern 
 us here and now). This first meaning is, after all, 
 the fundamental one, and we could hardly avoid 
 using the term in this way even if we used it also 
 in the other. 
 
 The noun "experienced^ is equivalent to the word 
 " consciousness,'' and we shall so use it, and shall use 
 the verb ^^tobe conscious of as equivalent to "to 
 
INTRODUCTION 7 
 
 experience/' *' Consciousness '^ meant originally 
 "the knowing that one knows/' "the experiencing 
 that one experiences/' to which we above referred 
 parenthetically; but it has completely lost in mod- 
 ern psychological usage that former restriction of 
 meaning. It is, however, used frequently in the 
 sense which we have given as the second meaning 
 of experience, namely: that which is apprehended 
 or known directly. Some authors with due notice 
 use the term in both senses, and others, we regret to 
 say, make similar usage without notification. Out- 
 side of psychology the historical meaning is still 
 in vogue to some extent, and the resulting misunder- 
 standing may be readily conceived. 
 
 "Knowledge" is a wider term than "experience" 
 or " consciousness," and our use of the former term 
 in defining the other two must be understood with 
 this qualification. It is only direct knowledge as 
 distinguished from indirect, that can be identified 
 as experience. The significance of this distinction 
 will become clearer later. 
 
 For that which we experience, or of which we are 
 conscious, we have the convenient and unambig- 
 uous term "content of consciousness'^ or "content 
 of experience." Frequently, however, we speak of 
 the "objects" of consciousness or experience, or of 
 
8 A SYSTEM OF PSYCHOLOGY 
 
 ^* psychological objects/' Thus, the sound which I 
 hear is a psychological object, as distinguished from 
 the air vibrations which cause it, which latter are 
 physical objects, and, as we shall see, are not 
 heard or experienced, although we may know of 
 them. 
 
 Other terms will be defined and explained in the 
 sections in which their comprehension can be made 
 most easy. 
 
 3. Extrinsic Helps 
 
 The proper preparation for the study of psychol- 
 ogy cannot be prescribed in a way that will cover 
 the needs of diverse individuals. One student will 
 make excellent progress while lacking certain ad- 
 vantages without which another sticks fast. The 
 elements of physics and of anatomy ought to be 
 understood, and the cell-physiology which is given 
 in the thorough courses in elementary biology or 
 physiology is of value. The student will get all 
 he needs of these subjects from good lecture and 
 demonstration courses in them, and, if after his 
 elementary course in psychology he decides to follow 
 it farther in some particular direction, he will then 
 discover in which of the sciences he needs laboratory 
 training. Perhaps the greatest need for the be- 
 
INTRODUCTION 9 
 
 ginner is an adequate training in literature, which 
 may be acquired by well-directed reading; for 
 psychology is least of all the subject in which any- 
 thing can be communicated or comprehended in a 
 special jargon or terminology, but requires all the 
 assistance that can be given by command of the re- 
 sources of the language of the masters in letters and 
 of the speech of the plainer men. After literary 
 training we should rank in importance a knowledge 
 of physics as a close second. 
 
 We have omitted the customary anatomical pict- 
 ures and discussions from this book, as the result 
 of deliberation and conviction. Cuts of the brain 
 and nervous system are readily accessible to any 
 student who cares to look at them, and it is better 
 for him to be sent to good anatomies to consult a 
 hundred pictures than to have a dozen or so chosen 
 out and put before him. Each instructor, more- 
 over, has his own choices of preparations, models, 
 charts, slides, and cuts, and of methods of presen- 
 tation of nervous anatomy and histology. A super- 
 ficial presentation here (and none other could be 
 given in the limits of this book) would be a posi- 
 tive detriment. The books and cuts suggested are 
 merely first aid to the student working alone. 
 
 Piersol's Human Anatomy; Howell's Text-Book 
 
10 A SYSTEM OF PSYCHOLOGY 
 
 of Physiology; Quain^s Anatomy^ vol. I, pt. II, and 
 vol. II, pts. II and III; Schafer's Text-Book of 
 Physiology, vol. II, and McKendrick and Snod- 
 grass's Physiology of the Senses are all valuable 
 aids in understanding the schematic anatomy of 
 the nervous system. Excellent plates of brain, eye, 
 and ear are given in the Sorbotta McMurrich Atlas 
 and Text-Book of Human Anatomy, vol. III. We 
 will give references chiefly to Piersol and Quain, 
 because one of these will doubtless be accessible to 
 the student. No specific references will be given 
 to McKendrick and Snodgrass because the book is 
 small, and appropriate material easy to find therein. 
 
 As for the general principles of nervous function, 
 the best brief account is found in Howell, chaps. 
 VI to XI, inclusive. The account of the nervous 
 system given in Piersol, beginning on page 996, is 
 especially valuable. For the needs of students of 
 psychology, however. Part First of Ladd and Wood- 
 worth's Elements of Physiological Psychology is 
 without doubt the best available general treatise on 
 the structure and functions of the nervous system. 
 
 On the physical problems of light and sound, 
 the articles by Lewis and Hallock, respectively, in 
 
 ^ The references are to the tenth edition of Quain, and 
 third edition of Howell. 
 
INTRODUCTION 11 
 
 Duff's Text-Book of Physics, will be found element- 
 ary and useful. Zahm's Sound and Music is an 
 intelligible and interesting treatise on acoustics. 
 Unfortunately, the more commendable treatises, 
 such as Barton's TexUBook on Sound, are too tech- 
 nical for the student who is not a specialist in phys- 
 ics. TyndalFs Lectures on Sound are still useful, 
 and Helmholtz's Sensations of Tone (Ellis's trans- 
 lation) is the starting-point for the student inter- 
 ested in the psychology of audition. 
 
CHAPTER II 
 
 PRELIMINARY ANALYSIS OF CONTENT 
 I. Complexity of Content and Complexity of Experience 
 
 The content of your experience at any given 
 moment in your life history is exceedingly complex. 
 As you sit reading this book you have visual im- 
 pressions of various forms and colors from the book 
 and from surrounding objects; you get various 
 sounds; odors; impressions of touch from the book 
 and from your clothing and chair; feelings in the 
 muscles, joints, eye-sockets, and viscera. All these 
 things are sensed or perceived, and simultaneously 
 something is thought of; e, g., the meaning of this 
 print is presented as a content of thought. Add to 
 these factors the emotional complexes of interest, 
 weariness, hunger, satisfaction, disgust, annoyance, 
 or whatever else is giving "tone" to your content, 
 and you begin to see the truth of the opening sen- 
 tence in this paragraph. 
 
 Although the content of experience is demonstra- 
 bly composed of a multitude of parts or elements 
 
 in complicated organic interrelation, it does not fol* 
 
 12 
 
PRELIMINARY ANALYSIS OF CONTENT 13 
 
 low that experience itself is complex. This has been 
 a stumbling-block for modern psychology because 
 of the frequent lack of clear distinction between 
 consciousness and its object. It is often said that 
 the content is not complex, but is simple and uni- 
 tary; and that the elements into which we apparently 
 resolve it by analysis are really new content brought 
 into existence by our analysis. In stricter language, 
 this really means that while the content which you 
 apprehend is complex, and may be resolved into its 
 elements, the apprehension or experience of the 
 content is not itself a complex made up of the appre- 
 hensions of the different elements. To this dogma 
 there is so far no reasonable objection, although it 
 may be found ultimately that even experience is 
 not so unitary as it appears to be; or rather, as it 
 suits our presuppositions to think it is. 
 
 2. General Classification of Elements of Content 
 In the examination of content of consciousness it 
 is important to ascertain as definitely as possible 
 how many sorts of elementary content there are. 
 By elementary content, or element of content, we 
 mean that portion of content which is not itself com- 
 plex; that is, which cannot in turn be analyzed into 
 component parts. Of such elements there appear 
 
14 A SYSTEM OF PSYCHOLOGY 
 
 to be four groups, each including a number of sub- 
 groups. Further investigation may show that at 
 least one of these groups must be fundamentally 
 revised, and perhaps eliminated, but we must give 
 them all consideration. These four kinds of con- 
 tent are sensations, relations, feelings, and images. 
 We will indicate briefly in the next paragraphs what 
 these terms cover. 
 
 Sensations are such things as color, sound, odor, 
 and warmth. Look at a drop of red ink on a paper 
 before you; the color — the red — abstracted from 
 its position on the paper, from its reference to other 
 objects, from its familiarity, from its likeness or 
 unlikeness to other colors; in short, from every- 
 thing but the color as presented, is a sensation. So 
 the sweet from sugar on the tongue, abstracted from 
 all the attendant impressions in the mouth, from 
 the fact that it is sugar, from the pleasantness, etc., 
 is a sensation. 
 
 It is one of the commonplaces of psychology that 
 a sensation is never presented alone to your ex- 
 perience. Neither is a mere group or complex of 
 sensations ever presented alone to the adult, and 
 probably not to the infant. Always there are 
 other elements, such as difference, familiarity, un- 
 pleasantness, etc., joined with it. Nevertheless, 
 
PRELIMINARY ANALYSIS OF CONTENT 15 
 
 we can pick out from among the mingled factors 
 of the complex the sensation itself and consider it 
 in detail. 
 
 Relations are easily recognized, or at least some 
 of them are. Similarity, difference, sequence, inter- 
 mediacy, possession, etc., are experienced just as 
 directly as are sensations. Perhaps the instances 
 given are not simple; perhaps they may be analyz- 
 able into simpler relations, but they are sufficiently 
 good specimens. 
 
 Feelings are most easily identified in emotions 
 or passions. Joy, sympathy, ennui, rage, hunger, 
 pleasure, are contents which involve complexes of 
 bodily sensations, relations, and in addition the 
 feelings which are their most important character- 
 istics. The total complexes named may all with 
 fairness be called emotions, and their analysis pre- 
 sents probably the maximum of difficulty with which 
 psychology has to contend. But it is reasonable to 
 conclude for the present that they cannot be com- 
 pletely accounted for without taking into account 
 elements of feeling. If it should eventually be 
 demonstrated that these feelings are nothing but 
 specific sensations, we will have neither done nor 
 suffered harm by listing them as elements or quasi- 
 elements. 
 
16 A SYSTEM OF PSYCHOLOGY 
 
 Images are generally considered as being the 
 "copies" or "revivals" of sensations and of com- 
 plexes of sensations previously experienced. Hav- 
 ing been conscious of the sensation of red under the 
 influence of physical light-waves you may later ex- 
 perience an "image" which is in some respects like 
 the sensation, and which will represent it. By the 
 images of sound, color, touch, and of sensations from 
 the muscles, we are enabled to "think" of content 
 which is not present; this is practically the doctrine 
 as Aristotle handed it down, and it is the doctrine of 
 current psychology. 
 
 We regret the necessity of departing radically 
 from established opinion, but feel the obligation to 
 warn our readers at once of our conclusion that the 
 belief in the existence of such forms of content is a 
 delusion, flowing partly from certain peculiarities of 
 consciousness and partly from metaphysical preju- 
 dices. We shall present the case in detail in the 
 proper place, not slighting the current theory. 
 
 3. Terminology 
 In contradistinction to content imagined, we speak 
 of content inhtited or apprehendedy and oppose in- 
 tuition or apprehension to imagination. Thus, 
 when light-rays fall upon my retina, I intuit a light 
 
PRELIMINARY ANALYSIS OF CONTENT 17 
 
 sensation. Sometimes the sensation is said to be 
 present as opposed to a sensation or other content 
 merely imagined. Perception appHes to intuition, 
 and to intuition plus imagination; usually it has 
 the latter reference. This will be clear to the reader 
 after he has studied the chapter on perception. 
 Intuition is popularly used to signify an occult or 
 inexplicable awareness of some fact; it is needless 
 to say that as we use the word it has no shred of 
 that meaning, which is a perversion of the correct 
 signification. 
 
CHAPTER III 
 
 SENSATION IN GENERAL 
 
 I. Sensation, Physical Stimulus, and Physiological 
 
 Process 
 
 Sensation — that which is experienced through 
 the senses, or through sense — must be distinguished 
 rigidly from the physical stimulus, on the one hand, 
 and the nervous activity which is caused by this 
 stimulus, on the other hand. The normal stimulus 
 is some activity of what we call "matter,'' usually 
 outside of, but acting on, the body of the individual. 
 Thus, the oscillation of the air particles which act 
 on the inner organs of the ear and produce sound; 
 the vibration of the ether which stimulates the ret- 
 ina of the eye and occasions the experience of light; 
 the chemical activity of substances, which produces 
 odor; these are instances of stimuli. There is little 
 difficulty in distinguishing stimuli from sensations, 
 even for the beginner, for a little reflection convinces 
 us that these physical facts are not experienced, 
 but only inferred. WTien, for instance, I hear a 
 tone, I am not conscious of the back-and-forth 
 
 movement of the air particles; and when I see a 
 
 18 
 
SENSATION IN GENERAL 19 
 
 color I am not experiencing the undulations of the 
 ether. In the latter case the stimulus is so far from 
 being experienced that it has required great labor 
 to discover its real nature (assuming that we do 
 know it now) by inferences from observations, and 
 it took years for those who held the present theory 
 to convince of error those who drew different con- 
 clusions from the observations. Even to-day phys- 
 icists do not profess to have a complete under- 
 standing of the actual behavior of the ether and 
 some of them doubt its existence. Yet an ignorant 
 man, who has never heard of ether, and whose views 
 on the transmission of light are amusing, may ex- 
 perience light and color sensations which are as 
 highly developed as those of any one. The smell 
 of a volatile substance depends doubtless on the 
 arrangement of the atoms in the molecules (or on 
 some such physico-chemical factor), but smell itself 
 gives no direct information as to this arrangement. 
 So it is throughout. What you experience through 
 the senses is not a material object, or any part of a 
 material object, although we have learned all we 
 know concerning material objects from a study of 
 the behavior of sensations. We have discovered dur- 
 ing the last ten centuries a great deal about the phys- 
 ical activities corresponding to most of our sensa- 
 
20 A SYSTEM OF PSYCHOLOGY 
 
 tions, and the general principles of their behavior; 
 which helps to create in the unreflective the belief 
 that we experience directly the physical activities 
 themselves. 
 
 The difference between the sensation and the 
 nervous process, especially that in the brain, is 
 harder to grasp than is the difference between sen- 
 sation and stimulus. This difficulty is at once ex- 
 emplified and increased by the fact that many physi- 
 ologists seem to teach that there is no difference. 
 
 The psycho-physiological confusion is rendered 
 well-nigh hopeless by the ambiguity of the term 
 " nervous process/' and though the ambiguity is not 
 dangerous in physiology, it is productive of much 
 trouble when physiology is brought into relation 
 with other studies. The terms " brain/' "nerve/^ 
 etc., may mean the actually experiencible; that is, 
 visible and tangible objects; and " nervous process,'' 
 accordingly, may signify changes which may act- 
 ually be watched, or which might be observed if 
 sufficiently delicate instruments were available. On 
 the other hand, the terms may signify the matter 
 and material changes which are supposed to be at 
 the basis of these observable things or changes, and 
 which, of course, we infer, but do not experience. 
 If, for example, someone could lay bare your brain 
 
SENSATION IN GENERAL 21 
 
 and with proper instruments observe the operations 
 of that mechanism, his sensations would be, loosely 
 speaking, brain processes; at least, the brain proc- 
 esses observed would be partly composed of his 
 sensations. But this is not what the physiologists 
 mean; they mean that your sensations, while you 
 observe anything whatsoever, are identical with your 
 brain processes. This meaning does not refer to 
 the brain processes in the first sense mentioned, 
 although often taken in that way, for no thoughtful 
 person would be guilty of supposing that while, for 
 instance, you are watching an indigo blue light, 
 that shade of blue could be discovered by obser- 
 vation of your brain cells. In general, if you could 
 watch the light (or other object), and at the same 
 time watch through some instrument all the changes 
 observable in the brain and nerve cells, you would 
 find practically nothing in common in the two ob- 
 jects. 
 
 The brain processes the physiologists mean when 
 they say that a sensation is a brain process are the 
 material facts and transformations which are not 
 observable directly as brain facts, but which we can 
 infer; in short, the things represented by the sym- 
 bols of chemistry. What you see, when you ex- 
 amine a nerve, are only sensations of light and color; 
 
22 A SYSTEM OF PSYCHOLOGY 
 
 what you feel are touch sensations; you do not see 
 or feel the matter of the nerve. The sensations 
 you experience and which you may suppose to be 
 the nerve under examination are really transforma- 
 tions in your own material nerves, which cannot be 
 experienced by anybody or anything except your 
 own " mind/* or perhaps can only experience them- 
 selves. Thus, the sensation, when followed relent- 
 lessly back in the physiological system of events, is 
 apparently found to have disappeared completely, 
 and to have been replaced by something else. 
 
 The vulgar way of accounting for this vanishing 
 of . sensations under scientific scrutiny is to suppose 
 that the "mind'* experiences these brain changes 
 and experiences them (wrongly, indeed,) as sensa- 
 tions. This is merely an unintelligent reversion to 
 an older and more respectable theory — that the 
 processes in the brain ^produce the sensations in the 
 " mind," — which theory does not identify the process 
 with the sensation. A more modern way is to say 
 that the brain process experiences itself. Thus, we 
 do away with the concept of "mind," except as a 
 name for a certain activity of brain cells and arrive 
 at a point of view which is apparently quite simple. 
 But this little subterfuge saves us only for a moment, 
 and either method of explanation, if consistently 
 
SENSATION IN GENERAL 23 
 
 adopted and carried out, lands us either in the con- 
 clusions of the Hindu Vedantists, that the world 
 which we seem to experience is not real but only 
 illusion; or in idealism, which holds Mind to be 
 the only reality. If we wish to hold to the theory 
 that there is a real world to experience, we must 
 hold that sensation is not brain state nor brain ac- 
 tivity. 
 
 The student will probably ask himself — very 
 likely has asked while reading this chapter — " Where 
 is sensation ?^^ The commonplace answer, ^*Itis 
 in the brain,^' seems to commit one to the doctrine 
 of sensation as a brain state; and yet, where else 
 can the sensation be? The sensation is not in the 
 brain unless the whole body is in the brain. Sup- 
 pose you have before you a red surface and ask your- 
 self, "Where is the red?^' Put your finger on the 
 surface, and the evident answer is, that it is where 
 the finger is; that is, "out there,'^ in space. Of 
 course, there is a possibility that you are deluded 
 in both cases, and that neither the color nor the 
 finger are "there,^^ but are both in the brain; or 
 rather, since the brain itself is in the same class with 
 the finger, the whole outfit is " in the mind." Thus, 
 if you begin by assuming that the sensations are in 
 the "mind," as opposed to a "real world," you will 
 
24 A SYSTEM OF PSYCHOLOGY 
 
 conclude in the end that the whole knowable uni- 
 verse is in the "mind/^ unless you are too busy, too 
 lazy, or too dull, to carry the process you have 
 started to its logical conclusion. If you are satis- 
 fied, and call this mental universe " real,'^ you have 
 reached idealism. If you are dissatisfied, and think 
 this does not give you reality enough, you have 
 reached the Hindu view of the world as Maya, or 
 illusion.^ 
 
 We do not feel either of these conclusions to be 
 satisfactory, and, therefore, are forced to assume 
 that sensations are not in the brain, but are where 
 they are experienced as being, or are so in many 
 cases. In some instances they may be at some 
 other point of space, and, hence, wrongly "lo- 
 cated'^; and there may indeed be in all cases a cer- 
 tain amount of error in location; but error is possible 
 here, as elsewhere, only if there is a basis of correct- 
 ness. 
 
 If it should be proven that what we call "out 
 there ^' is really in the mind, then our analysis is 
 still true, for the sensation is "out there" in so far 
 as there is any " out there." This whole matter is 
 
 ^ If sensations are brain states, or "in the mind," so are all 
 other experiencible elements and complexes; and we expe- 
 rience nothing which is outside the brain (or mind). 
 
SENSATION IN GENERAL 25 
 
 subject to many sophistical difficulties which it re- 
 quires clear philosophy to dispel, but for the pres- 
 ent the student need not abjure his naive common- 
 sense view, which will not in any event vitiate his 
 analysis, whereas the opposite view certainly would 
 be risky. The illusion theory and the idealistic 
 hypothesis, are not necessary for science or psy- 
 chology. 
 
 2. Matter and Psycho-Physical Causation 
 
 Understanding that sensation is not the same 
 thing as the stimulus which may physically cause 
 it, and is not the same thing as the brain and nerve 
 processes which may also be said to cause it, we still 
 find it useful and necessary to treat of sensation 
 and other mental processes in relation to both of 
 these. The question of the ultimate relation of the 
 mental to the material, with its more or less def- 
 inite answers of "parallelism,^' " interactionism,'' 
 " materialism,^' etc., will be of interest and impor- 
 tance to the student as he goes deeper into psychol- 
 ogy, but are so far from being essential at the start 
 that a considerable knowledge of psychology is 
 necessary before he can take up these matters in- 
 telligently. It is at present no business of ours to 
 decide whether matter actually exists as substance. 
 
26 A SYSTEM OF PSYCHOLOGY 
 
 or whether it is only a convenient fiction, or whether 
 it exists in the Huxleyan sense as the universally 
 valid law of the content of experience. We must 
 hold the concept of matter as scientifically indis- 
 pensable/ at least for the present, and take it into 
 consideration when dealing with the facts of experi- 
 ence. The author is personally convinced of the 
 correctness of Huxley^s theory, which has the weight 
 of centuries of philosophy behind it; but nothing in 
 the present volume should be any the less harmoni- 
 ous with your postulates if you hold that matter is 
 an actual thing or substance, or hold some other 
 view; because none of our psychological analyses 
 depends on any such assumption. 
 
 On the other question, which is frequently con- 
 fused with the one as to the nature of matter and 
 its relation to experiencible things;^ on the ques- 
 tion, that is, of the relation between the experience 
 and its content and the brain activities which ac- 
 company this experience, and which may them- 
 selves be made the content of experience, we must 
 take the common-sense view that the relation is one 
 
 ^ By " matter '^ is meant either the atoms and ether, or what- 
 ever physical science replaces these with. "Energy'' must 
 also be included, or else assumed in addition. 
 
 2 This confusion furnishes practically the whole substance 
 of the time-honored dispute between the " interactionists " 
 and the "parallelists." 
 
SENSATION IN GENERAL 27 
 
 of cause and effect, although we know very little 
 about the real nature of causation, here or elsewhere, 
 and are moreover unable to find out just how the 
 causal sequences occur in these cases. If any one 
 is prejudiced the other way, and is determined to 
 believe that there is no causal relation between brain 
 and experience, he will probably find few instances 
 herein in which our supposition makes less accept- 
 able for him our exposition of facts and principles. 
 
 3. The Lag of Sensation 
 
 The sensation may or may not begin simulta- 
 neously with the process in the cerebral cortex; 
 there is no direct evidence on this point. Between 
 the initial action of the stimulus on the end-organ, 
 and the beginning of the sensation, there is an in- 
 terval which we suppose to be due primarily to the 
 time required to set in action the end-organ, the 
 nervous path of conduction, and the cerebral ap- 
 paratus successively. When the stimulus ceases to 
 act on the end-organ, the sensation does not cease 
 at once, but continues for a brief time; this per- 
 sistence we suppose to be due to the fact that the 
 neural apparatus continues in action after the dis- 
 continuance of the stimulus. 
 
 With a given strength of stimulus, the time re- 
 
28 A SYSTEM OF PSYCHOLOGY 
 
 quired for the sensation to reach its maximal in- 
 tensity after the beginning of the stimulus is less 
 than the time required for the sensation to disappear 
 after the cessation of the stimulus. The time re- 
 quired to raise the sensation to any point of inten- 
 sity lower than the maximal is less than the time 
 the sensation will last after it reaches that same 
 intensity in the dying-out process. 
 
 The delay in the rise of the sensation to a maxi- 
 mum, or to a definite point below the maximum, we 
 designate as the initial lag of the sensation. The 
 time required for the dying out of the sensation, 
 from the point at which the stimulus ceases, is 
 called the terminal lag. The terminal lag is greater 
 than the initial lag, however the initial lag is de- 
 fined in a particular case. 
 
 We take practical advantage of the excess of the 
 terminal lag over the initial lag in the mixing of 
 colors by means of revolving discs. If the disc re- 
 volves so fast that the retinal processes excited by 
 a sector in any retinal area do not diminish appre- 
 ciably in interisity before the sector again stimulates 
 the same area, the effect is exactly the same as that 
 of a constant stimulus, and, therefore, the sensation 
 is steady. The initial lag operates in this case to 
 effect a reduction of the intensity of the sensation 
 
SENSATION IN GENERAL 29 
 
 below that which would obtain if the stimulus acted 
 continuously. The passage of the sector across the 
 point in the visual field occupies so brief a time (if 
 the colors blend well) that before the physiological 
 process has been raised to its full intensity the sec- 
 tor has gone by. The intensity of the sensation 
 produced by the intermittent stimulation is about 
 the same as the intensity produced by the constant 
 action of a stimulus bearing the same intensity ratio 
 to the intermittent stimulus as the length of time 
 the intermittent stimulus is present bears to the 
 total time.^ This generalization is known as the 
 Talbot-Plateau law. Possibly there are limitations 
 to be made, but none are yet established. 
 
 The other modes of sense are theoretically sub- 
 ject to lag, and its occurrence may be demonstrated 
 in the cases of audition and the dermal senses. 
 Where the intermittence of a tone is rapid enough, 
 the sensation becomes continuous and steady. And 
 
 ^ For example : A light stimulus which is so intermitted 
 by means of rotating sectors, or otherwise, that the half- 
 phase from disappearance to reappearance is exactly as long 
 as the half-phase from reappearance to disappearance, will 
 appear as bright as a stimulus of half the intensity contin- 
 uously present. The frequency of intermittence necessary 
 to produce a "smooth" mixture, ^. e., to avoid flicker, is in 
 many cases over sixty per second; with dimmer lights a 
 slower rate will succeed. This rate gives us no idea of the 
 actual magnitude of either initial or terminal lag, but throws 
 some light on the relation of the two. 
 
30 A SYSTEM OF PSYCHOLOGY 
 
 a rapid succession of taps on the finger will fuse 
 into a steady sensation. 
 
 Intermittence of a stimulus modifies in an essen- 
 tial way the resulting sensation or sensations. This 
 modification is in some circumstances noticeable in 
 light as a variation in quality, but is still more 
 marked in the case of tones, because a large part of 
 the range of the rates of sound vibration is within 
 the range of intermittences which can be employed. 
 The practical effect of intermitting a tone stimulus 
 is to add to the sensation another tone having a 
 pitch corresponding to the rate of intermittence, 
 provided the said rate is faster than circa thirty per 
 second. Below thirty, the result is merely the pro- 
 duction of beats. It is sometimes said that the 
 beats "fuse into a tone" when they become suf- 
 ficiently rapid; there is no reasonable objection to 
 that form of statement for the present. The new, 
 or secondary, tone arises when two sources of sound 
 differ by more than thirty vibrations per second, as 
 well as when a single tone is mechanically inter- 
 mittent; the tone in the one case mentioned is ac- 
 cordingly called a difference tonCy and in the other 
 an intermittence tone. There are difference tones 
 of the first and second orders, corresponding to the 
 two orders of beats. 
 
SENSATION IN GENERAL 31 
 
 The production of a tone by a sound-wave is 
 itself sometimes spoken of as the fusion of the 
 processes aroused by intermittent stimulation, the 
 sound-wave being considered as an intermittent 
 affair. This is an error, for the sound-wave, when 
 rapid enough to produce a tone sensation, is strictly 
 a continuous stimulus. 
 
 4. Secondary Sensations 
 
 In many cases the sensation aroused by a given 
 stimulus is followed by a secondary sensational con- 
 tent, after the cessation of the stimulus in question, 
 and without further essential stimulation. The sec- 
 ondary sensation follows its primary sensation after 
 an interval varying from a fraction of a second to 
 several seconds. It may be of the same quality as 
 the primary, or it may be of some other quality of 
 the same mode. 
 
 The secondary sensation is commonly called an 
 "after-image," and is said to be "negative" when 
 complementary in color, or opposite in temperature, 
 to the primary sensation, and "positive" when of 
 the quality of the primary. It is unfortunate that 
 we have not a better terminology for these phe- 
 nomena, for it is important that the secondary 
 sensations be distinguished from the negative after- 
 
32 A SYSTEM OF PSYCHOLOGY 
 
 images described in the chapter on sensation qual- 
 ity/ The true negative after-image is produced by 
 a stimulation which may be called secondary, since 
 it follows the stimulus which conditions the pre- 
 ceding sensation, and its operation depends on the 
 results of that stimulus; but as a sensation, it is 
 just as primary as the preceding sensation. 
 
 Secondary visual sensations develop best after 
 a brief stimulation by a strong light. Gaze for a 
 moment at a gas flame, or electric light filament, 
 and then turn out the light, having the room other- 
 wise completely darkened. In a few moments an 
 ^' image of the light^' will appear, perhaps in its nor- 
 mal color, perhaps in some other; it may seem mi- 
 nute in size, and located in the eye itself; by a little 
 practice you can succeed in projecting it to a dis- 
 tance, when it will seem correspondingly large. A 
 very slight movement of the eye will cause the sec- 
 ondary sensation to disappear temporarily. 
 
 5. The Characters of Sensation 
 
 If we consider a single sensation, e. g., a certain 
 red, and compare it with others, e, g., sweet or blue, 
 we find that, although the sensation cannot be 
 analyzed or resolved into simpler objects, and, there- 
 
 ^ Chap. IV, § 8. 
 
SENSATION IN GENERAL 33 
 
 fore, is properly called elementary, yet it is not so 
 simple that it has not several different aspects, or 
 points of difference from other sensations. These 
 aspects, or points of difference, are usually called 
 characters, and a proper understanding of these 
 characters is the indispensable foundation of the 
 study of sensation. 
 
 In the first place, a certain red differs from sweet 
 and blue in a way in which it does not differ from 
 other reds. This difference we call one of quality. 
 It is a difference in kind of sensation. Next, there 
 is a difference between certain reds of the same 
 quality, as well as between reds and any other sen- 
 sations, which we call intensity. We may increase 
 the brightness of red without bringing any other 
 color or sensation, so far as is observable. (In 
 most cases, however, changing the intensity of a 
 color involves the changing of the quality also, to 
 some extent.) A spoonful of sugar in a glass of 
 water will give a taste which is weaker (less intense) 
 than two spoonfuls; and though we commonly say 
 it is less sweet, we do not mean that the quality is 
 different, but that the intensity is less.^ The weak 
 
 ^ The same language in regard to other sensations may 
 mean a difference of quality, rather than of intensity. Thus, 
 to say a light is less red than another usually means that it 
 contains more of some other color. 
 
34 A SYSTEM OF PSYCHOLOGY 
 
 sweet is no more like bitter or blue in quality than 
 is the more intense sweet. 
 
 A third character of sensation is volume or ex- 
 tensity. A large patch of light differs from a small 
 one even if of the same color and intensity. So a 
 large touch on the skin differs from a small one. 
 Similar differences may be found in muscular and 
 auditory sensations, but that they may be found in 
 all kinds cannot be said dei&nitely. Smell sensa- 
 tions do not seem to have this character at all, and 
 its presence is an open question with regard to 
 taste. Extensity is sometimes confused with ex- 
 tension, or perceived space; but in the latter the 
 former is only one factor, as will be shown in the 
 proper place. Extension is a function of a com- 
 plex content, but extensity is just as original an as- 
 pect of those sensations which possess it at all as are 
 quality and intensity. 
 
 The fourth aspect is duration, or protensity. 
 Just as most sensations have extensity or inchoate 
 bigness, which forms the beginning of our knowl- 
 edge of space, so all have a magnitude of another 
 sort which forms the basis of our perception of 
 time. No sensation can be conceived which has 
 not this temporal or enduring character. It may 
 be roughly indicated by saying that a sensation 
 
SENSATION IN GENERAL 35 
 
 which lasts no time at all does not exist. This, 
 however, gives a slightly false implication, since 
 the protensity of a perception does not imply the 
 perception of time as such.^ 
 
 Some sensations possess the important character 
 of local significance. Thi ^ is an aspect which can- 
 not be directly demonstrated, but which can, never- 
 theless, be conclusively proved to exist. It is the 
 character of a sensation by which, independently 
 of its other aspects, we are able to determine the 
 part of the body in which the neural process 
 originates, or the direction in space from which 
 the stimulus comes. The sensation from each 
 part of the skin and retina has its peculiar local 
 sign. 
 
 Any sensation may be pleasant or unpleasant. 
 By considering the neutral condition, in which 
 there is neither positive pleasantness nor unpleas- 
 antness, as simply the transitional point between 
 the two, we may consider the triad as an aspect 
 of sensation which is usually called feeling-tone. 
 This so-called character is not strictly on a par with 
 the ones previously enumerated, because, in the 
 
 * Protensity is not quite the same as duration, in the com- 
 mon acceptation of the term. This will be made clear in 
 the section on time-perception. 
 
36 A SYSTEM OF PSYCHOLOGY 
 
 first place, it can be considered as an accompani- 
 ment of sensation, which the others cannot, and in 
 the second place it is equally attached to other 
 features of the content of experience besides sen- 
 sations, in which cases it seems still more clearly 
 to be an accompanying factor rather than an as- 
 pect. 
 
 The characters just named seem to exhaust the 
 list. We find no other aspects under which sensa- 
 tion must be viewed in and for itself, although of 
 course we find it functioning in definite ways in the 
 total content, and entering into different relations to 
 consciousness. The catalogue stands then: quality, 
 intensity, protensity, extensity, local significance, 
 with possibly feeling-tone. 
 
 In an advanced study of the psychology of sen- 
 sation it is advisable to take up each group of 
 sensations by itself, and to give it exhaustive treat- 
 ment from all sides. In an elementary study, 
 where the general principles are more important 
 than the minute details, and in particular where 
 sensation is studied in its connection with other 
 content and with experience rather than for its 
 own interest, the systematic treatment under the 
 different aspects or characters is more useful. We 
 shall, therefore, treat sensation first under its qual- 
 
SENSATION IN GENERAL 37 
 
 itative aspect, and then under the other aspects in 
 order. Such a programme cannot be adhered to 
 absolutely, and there will necessarily be some over- 
 lapping. 
 
CHAPTER IV 
 
 SENSATION QUALITY 
 I. General Classification 
 
 The various qualities of sensation are commonly 
 divided into groups, each of which is said to "be- 
 long to" a definite sense. Red, green, and blue, 
 for example, belong to the sense of vision and are 
 called visual sensations. Bitter and sweet belong 
 to the sense of taste, or gustation, and are called 
 gustatory sensations. 
 
 It is sometimes said that there are five senses, 
 but as a matter of fact we discriminate several 
 more than that number. There is much confusion 
 in regard to the names applied to several of the 
 senses and to the sensations which appertain 
 to them, and still more confusion in the names 
 applied to the sensibility or insensibility to certain 
 sorts of sensation. The terms given in the follow- 
 ing table represent the most justifiable usage, al- 
 though not in all cases the most common: 
 
 38 
 
SENSATION QUALITY 
 
 39 
 
 THE TERMINOLOGY OF SENSATION 
 
 I 
 
 II 
 
 Ill IV 
 
 V 
 
 SENSE 
 
 ADJECTIVES 
 
 ANESTHESIA 
 
 Taste. 
 
 Gusta- 
 tion. 
 
 Gusta- 
 tory. 
 
 Geusic. 
 
 Ageusia. 
 
 SmeU. 
 
 Olfaction. 
 
 Olfactory. 
 
 Osmic. 
 
 Anosmia. 
 
 Sight. 
 
 Vision. 
 
 Visual. 
 
 Opsic. 
 
 Anopsia. 
 
 Hearing. 
 
 Audition. 
 
 Auditory. 
 
 Acusic. 
 
 Anacusia. 
 
 Touch. 
 
 Taction. 
 
 Tactual. 
 
 Haphic. 
 
 Anaphia. 
 
 Warmth-sense. 
 
 
 
 
 Thalpotic. 
 
 Athalposia. 
 
 Cold-sense. 
 
 
 
 
 Rhigotic. 
 
 Arrhigosia. 
 
 Tickle-sense. 
 
 Titilli- 
 
 Titilli- 
 
 Gargal- 
 
 Gargal- 
 
 
 ation. 
 
 atory. 
 
 sesthetic. 
 
 anaesthesia. 
 
 Muscle-sense. 
 
 
 :;::::! 
 
 Kin aesthetic. 
 
 Akinaesthesia. 
 
 Joint-sense. 
 
 
 
 
 Body-sense. 
 
 
 
 Coensesthetic. 
 
 
 Pain-sense. 
 
 
 
 Algetic. 
 
 Analgesia. 
 
 Hair-sense. 
 
 
 
 
 Tricho- 
 aesthetic. 
 
 Tricho- 
 anaesthesia. 
 
 Vibration-sense. 
 
 
 
 Palmaesthetic. 
 
 Palman- 
 aesthesia. 
 
 The first column contains the names for the 
 senses, derived from various languages. In the 
 second column are the corresponding words of 
 Latin derivation. The third column gives the 
 adjectives applying to the sensations. In a case 
 where there is no specific adjective, the usual Eng- 
 lish sense name is used adjectively; e, g., pain 
 sensation, cold sensation. The adjectives from the 
 Greek, given in the fourth column, indicate the 
 sensibility, and should not be used to indicate 
 either the sense or the sensation. 
 
 The prefixes jpar- (para-), pseud-, (pseudo-), hyp- 
 {hypO"), and hyper- are also used with the Greek 
 
40 A SYSTEM OF PSYCHOLOGY 
 
 words (with the ia termination) to indicate specific 
 aberrations of sensibility; as, for example, parop- 
 sia, pseudosmia, hypokincesthesia. The prefix orth- 
 (ortho-) is used to indicate the normal condition of 
 the sensibility, as for example orthacusia. The 
 suffix -meter is added to indicate the instrument for 
 measuring the sensibiUty; for example, acumetery 
 haptometer , algesimeter. Certain sense realms have 
 also special prefixes to indicate peculiarities of sen- 
 sibility found in these realms. Chromopsia, for 
 example, indicates sensitivity to color; achromopsia 
 indicates color-blindness; and for various aberra- 
 tions of color sensitivity we have the terms para- 
 chromopsia n dichromopsia, etc/ 
 
 Each sense has its own end-organ or organs; 
 that is, some mechanism for receiving physical stim- 
 ulation and transmitting excitation to the brain; 
 this is true both anatomically and histologically. 
 But the sense cannot be defined by reference simply 
 to the organ in either meaning. Some organs 
 (grossly speaking) are vehicles for more than one 
 
 ^ The system of terminology for sense-psychology given 
 above is the logical one, and is in common use, except for the 
 terms for temperatm-e sensations. This system, however, 
 is not exclusively used, there being the most deplorable con- 
 fusion in regard to terms for almost all of the senses. Cer- 
 tain terms are used by different authors in exactly opposite 
 senses, and for some cases we have a variety of terms in use. 
 
SENSATION QUALITY 41 
 
 sense. The eye gives visual, muscular, and temper- 
 ature sensations; the ear auditory and organic as 
 well as tactual; the tongue gustatory, tactual, and 
 cold and warm sensations; the nose also gives tactual 
 and cold and warmth as well as olfactory sensations; 
 the skin gives several sorts of sensations. 
 
 We might use the term organ in a narrower 
 sense and say that the retina is the organ of vision, 
 the cochlea the organ of hearing, etc., but this 
 would be inaccurate; because the whole ball of the 
 eye and its muscles are functionally concerned in 
 vision, and form the organ; and so likewise the 
 bones, membranes, and muscles, of the ear-drum 
 are entitled to be specified as parts of the organ of 
 hearing, since they participate normally in the pro- 
 duction of the nervous process which conditions the 
 experience of sound. 
 
 If we wish to associate the visual sensation with 
 its specific nervous terminals, excluding the acces- 
 sory parts of the organ, we should have to take, not 
 the retina as a whole, but the minute rods and 
 cones therein, into consideration. In the same wav 
 we should consider only the hair-cells in the basi- 
 lar membrane of the inner ear in connection with 
 auditory sensations. We might, therefore, with accu- 
 racy specify visual sensations as those presented 
 
42 A SYSTEM OF PSYCHOLOGY 
 
 through the activity of the nerve endings in the 
 retina of the eye, and so on; and to this method of 
 speech there can be no reasonable objection; but 
 it gives no information about the sensations them- 
 selves beyond the connection explicitly designated. 
 It neither defines nor specifies the sensations, but 
 presupposes their identification. 
 
 The term '' sense '' is used very loosely. Some- 
 times it indicates the group of sensations, sometimes 
 the abstract possibility of experiencing these, and 
 sometimes the entire physiological mechanism for 
 the experience, including the histological organ. 
 Accordingly, psychologists are accustomed to use 
 the term "mode of sensation ^^ to convey with pre- 
 cision the first of these meanings. The visual sen- 
 sations taken as a group are said to constitute the 
 visual mode of sensation; the olfactory sensations 
 the olfactory mode, and so on.^ Modality is one 
 step above quality in the logical classification of 
 sensations. 
 
 * Helmholtz defined a mode as a group of sensations related 
 so closely that it is possible to pass from one to the other by 
 a gradation so minute as to be practically continuous. (Hand- 
 buch der physiologischen Optik, 1894, § 584.) This will be 
 illustrated in section 6 of this chapter, in the case of visual 
 sensations. The definition is not useful, since it gives no 
 criterion for distinguishing a transition between two sensa- 
 tions of the same mode from a transition between two sen- 
 sations of different modes; hence the modality has always 
 
SENSATION QUALITY 43 
 
 2. Sensation and Brain Process 
 Each sensation quality depends on a specific 
 kind of nervous process in the cortex of the brain, 
 and each mode of sense seems to be dependent upon 
 the functioning of a definite part of the cortex, which 
 is called the " cortical centre," for that mode. Each 
 mode, and perhaps in some modes each quality, is 
 represented by certain peripheral nervous structures 
 called "end-organs," and these are connected by 
 sensory nerves with the corresponding centres.^ 
 
 The cells of the sensory cortex are specialized to 
 respond to the excitations poured in upon them by 
 the end-organs with which they are connected. 
 Whether they would (in the case of an adult) re- 
 spond to a different kind of stimulation, is a matter 
 for doubt. In the plastic condition of the develop- 
 ing cortex (of the infant) it seems to be a fact that 
 
 to be distinguished on other grounds. A continuously graded 
 transition from heat to bitter, for instance, is perfectly possi- 
 ble, and there would be no objection to considering it a 
 transition within a mode, if we had not decided, on grounds 
 having no reference to the question of gradations, that bitter 
 belongs to one mode, and heat to another. The final deci- 
 sion on a question of modality of elementary sensations 
 must rest on the likeness and unlikeness of the sensations 
 involved. 
 
 1 See Howell, figs. 96-100, and pp. 198-228. Piersol, figs. 
 102 and 1043; also figs. 1041, 1044, 909, 910, 987, 988. 
 Schafer, figs. 330, 338, 340 and 351. 
 
44 A SYSTEM OF PSYCHOLOGY 
 
 if certain cells which would normally respond to a 
 definite sort of stimulation, e, g,, visual, be de- 
 stroyed, other cells, either in the cortex or in the 
 lower centres, may become so adapted as to respond 
 to that sort of stimulus. In any case, it is the kind 
 of stimulus furnished to the brain cell by the end- 
 organ which determines its response. Direct irri- 
 tation of the cells of the cortex by electrical currents, 
 or by pinching or burning, produces no sensation. 
 The character of the process in the end-organ is the 
 thing of prime importance in determining the sen- 
 sory function of the brain cell. 
 
 3. Sensation of Taste 
 Gustatory sensations are dependent on the stim- 
 ulation of certain nerve endings, almost all of which 
 are on the tongue. These nerve endings are in the 
 "taste-buds," which are the peripheral organs of 
 taste. They are found on the tongue in the walls 
 of the circumvallate papillae and in the fungiform 
 papillae, and also occur in the epithelium of the 
 mucus membrane where there are no papillae.^ In 
 the cases of infants and some adults a few taste- 
 buds are found on the soft palate, gums, cheek- 
 linings and even on the tonsils and hard palate. 
 
 ^Piersol, figs. 1193, 1194, 1195, 1196, 1197; Quain, III, 
 pt. Ill, figs. 167, 168, 170, 172. 
 
SENSATION QUALITY 45 
 
 The cortical centres for taste, or gustatory cen- 
 tres, are on the inner sides of the hemispheres, 
 probably in the hippocampal lobes. The course of 
 the nerve-fibres from tongue to cortex is extremely 
 complicated. One bundle runs through the tym- 
 panum (ear-drum), and is hence called for that 
 portion of its course the "chorda tympani.'' ^ 
 
 Substances which are gustable (sapid substances) 
 must be dissolved in water (or in some aqueous 
 liquid; saliva is, of course, the common solvent), 
 and so either enter the outer part of the taste-bud, 
 or perhaps come in contact with the hair-like fibres 
 of the gustatory cells projecting into the orifice 
 leading to the bud. Substances insoluble in water 
 are tasteless; but soluble substances are not always 
 gustable. 
 
 Although the number of "flavors" detectable in 
 substances introduced into the mouth is indefinitely 
 large, there are probably but four distinct element- 
 ary taste quaHties. These are: sweet, salty, bitter, 
 and sour ("acid"). These are the only sensations 
 (except possibly "metallic" and another to be 
 noted later) referable to the taste-buds, and are the 
 only ones to be called tastes. The so-called "al- 
 kali" taste is probably a combination of weak salty 
 iPiersol, figs. 1075 and 1079; Howell, fig. 119. 
 
46 A SYSTEM OF PSYCHOLOGY 
 
 with weaker bitter. " Hot " tastes, as of pepper, are 
 due to the excitation of non-gustatory end-organs 
 on the tongue and in other parts of the mouth, and 
 are genuine warmth sensations, like those obtain- 
 able from the skin of the hand or arm. The tongue 
 is also sensitive to cold, and to touch; peppermint 
 excites indirectly sensations of the former, and "as- 
 tringent" substances, as alum and strong tea, ex- 
 cite those of the latter. But the characteristic thing 
 about what we call flavor in foods and drink is given 
 through the sense of smell, as may be demonstrated 
 in many ways. Every one has noticed the com- 
 parative tastelessness of food during the course of 
 a severe cold; this is the result of the interference 
 of the catarrhal inflammation with the function of 
 the organs of smell. Conclusive results may be ob- 
 tained readily by stopping up the outer opening 
 of the nostrils (anterior nares) and the inner open- 
 ing (posterior nares) .^ The patient then breathes 
 through the mouth and no aroma can possibly as- 
 cend to the nostrils. The patient in the condition 
 described is temporarily anosmic. If his eyes are 
 
 * The posterior nares, of course, should not be meddled with 
 except by a physician. But one can obtain fairly good re- 
 sults by stopping the anterior nares alone (with pieces of 
 cotton) provided the patient breathes gently. Vigorous 
 breathing increases the diffusion of odorous substances into 
 the nose through the posterior nares. 
 
SENSATION QUALITY 47 
 
 shut, he can distinguish substances put into his 
 mouth only in so far as they differ in regard to the 
 five qualities we have mentioned, or in regard to 
 their "feel'' (touch), or temperature. A few in- 
 stances will illustrate. Tea, weak coffee, and a 
 solution of quinine cannot be told apart if the 
 strength of each is properly chosen. If the tea is 
 very strong, the quinine solution may require a drop 
 of alum water to be added to it to make it taste like 
 the tea. Plain sugar and water cannot be distin- 
 guished from molasses or almost any fruit syrup, 
 properly diluted. Suitable mixtures of grain alco- 
 hol and water, with sugar, and a few drops of alum 
 water and vinegar (or acid-solution), as necessary, 
 will counterfeit vinous or distilled liquors. These 
 experiments may be extended indefinitely, and not 
 only demonstrate the fewness of taste qualities, but 
 will also show how very sensitive the tongue is to 
 touch and to temperature, and how much our dis- 
 crimination depends on these. It is well not to let 
 the patient taste the solutions before his nostrils are 
 stopped, or slight differences in viscosity, or strength 
 of any element, may cause him to remember and 
 distinguish them later, with no intention of trickery 
 on his part. 
 
 The functions oi- individual taste-buds have not 
 
48 A SYSTEM OF PSYCHOLOGY 
 
 been satisfactorily examined, but experiments which 
 have been made on single papillae (fungiform) show 
 that some of them are sensitive to two qualities only, 
 some to three, and some to only one, although there 
 is some doubt whether there are papillae sensitive 
 to bitter only. Seldom are papillae sensitive to 
 all four qualities. Whether a single taste-bud 
 can produce the nervous excitation of more than 
 one taste quality is for the present an open ques- 
 tion. 
 
 The circumvallate papillae, and others near the 
 base of the tongue, are especially sensitive to bitter. 
 Papillae sensitive to sweet are grouped more numer- 
 ously toward the tip of the tongue, and those sensi- 
 tive to salt and sour on or near the edges. Sensi- 
 tive papillae are few in the central area of the tongue, 
 which some experimentors have reported as com- 
 pletely ageusic; but, in general, all parts of the 
 upper surface of the tongue possess some of the 
 papillae sensitive to each of the gustatory qualities, 
 although the details of distribution differ with the 
 individuals, and some persons are, through disease, 
 rendered totally ageusic. 
 
 There is one content of experience which is com- 
 monly called a "taste" which merits special atten- 
 tion, since it is not included in any of the conditions 
 
SENSATION QUALITY 49 
 
 we have here described. This sensation, or com- 
 plex, which every one, no matter how temperate, 
 has doubtless experienced, is commonly known by 
 the picturesque name of the '* dark-brown taste/' 
 It certainly is not salt, sweet, or sour, and the bitter, 
 metallic or astringent components, if present, are 
 not the main thing. Although due to visceral con- 
 ditions, it is probably produced through stimulation 
 of the nerves in the mouth, and so may have a cer- 
 tain claim to be classed as a taste sensation. But 
 there are other reasons why it may be classed with 
 the organic sensations (ccensesthesia), and we shall 
 discuss it further under that head. 
 
 4. Sensations of Smell 
 
 If the student looks on the nose as the organ of 
 smell, with no further idea of the exact part of the 
 nose which is sensitive, he will be somewhat sur- 
 prised upon examining the nasal structure. The 
 interior of the nose is a complicated cavern, or 
 rather two caverns, communicating not only with 
 the outer air and with the pharynx, but with cavi- 
 ties in the bones of the face. The peripheral ner- 
 vous apparatus of smell occupies only a very small 
 area in the membrane covering a part of the supe- 
 rior turbinal bone and of the adjacent portion of the 
 
50 A SYSTEM OF PSYCHOLOGY 
 
 nasal septum. This region is known as the olfac- 
 tory region, and this portion of the membrane as 
 the olfactory membrane. The cells which receive the 
 terminations of the nerve fibres are much like the 
 gustatory cells of the taste-buds.^ 
 
 The fibres of the olfactory nerve penetrate di- 
 rectly through the skull to the olfactory lobes of the 
 brain, and pass thence to the hippocampal lobe, 
 especially the distal portion thereof, called the gyrus 
 uncinatus. This is, therefore, the cortical centre 
 for smell — the olfactorv centre. 
 
 In order that it may be smelled, a substance must 
 be in a gaseous state, and must be brought into 
 direct contact with the olfactory membrane. How- 
 ever fine may be the particles of a substance, if they 
 remain mere particles, not becoming vaporized, they 
 are without odor. Formerly it was thought that 
 substances dissolved in water could be smelled if 
 brought in contact with the membrane, but now it 
 is known that such is not the case. Substances 
 that are odorous also fulfil a definite chemical con- 
 dition; the molecules which constitute them must 
 
 ^ On nose and peripheral terminations see Piersol, figs. 
 1174, 1175, 1176, 1178, 1179, 1180; Quain, III, pt. Ill, figs. 
 154, 156, 157, 158, 159, 160; Schafer, figs. 446, 447. On the 
 neural connections, Piersol, figs. 1042, 1043, 1047, 1048, 1049; 
 Howell, fig. 95; Schafer, figs. 351, 349. 
 
SENSATION QUALITY 51 
 
 possess or exceed a certain minimum weight. This 
 minimum is for most persons the weight of prussic 
 acid (hydrocyanic acid), which substance is odor- 
 less for these individuals. Other persons, whose 
 osmic sensitivity extends slightly lower, find that 
 prussic acid has a distinct odor. 
 
 Constant presence may render any substance 
 odorless; that is, an odor continuously present, 
 finally disappears. Water vapor and carbon di- 
 oxide, although gaseous and of suflBcient molecular 
 weight, are odorless because always in the air. 
 This is probably an instance of what is best desig- 
 nated as protective adaptation. A sensory organ 
 acted upon by a stimulus which it is functionally 
 fitted to receive becomes by the action of the stim- 
 ulus less responsive to it. This is not fatigue, which 
 of course may produce a similar result; it is an 
 antagonistic reaction by which the organ becomes 
 protected against the action of the stimulus, just as 
 the soles of the feet become protected by thicken- 
 ing of the skin when no shoes are worn. The quick- 
 ness and completeness with which one becomes 
 insensitive to an osmic stimulation is a matter of 
 common observation. The air in the room be- 
 comes fetid from one of a number of causes, and 
 you do not notice it until you return after being 
 
52 A SYSTEM OF PSYCHOLOGY 
 
 out of the room some moments. People are, in 
 general, immune to the odor of their own per- 
 spiration. 
 
 The number of elementary olfactory qualities is 
 at present unknown. We are obliged to treat them 
 as if they were indefinitely numerous, and yet there 
 may be really only a few, which by combination in 
 endlessly different ways give rise to the riotous pro- 
 fusion of odors which constitute our olfactory world. 
 The suggestive similarities which run criss-cross 
 through this world point to this theory, but so far 
 we have not been able to make any scientific use 
 of those similarities. Classification by qualitative 
 affinity has been attempted; a great many natural- 
 ists since Aristotle have tinkered with the problem ; 
 the most laudable attempt being made by the bot- 
 anist Linnaeus, to whose catalogue Zwaardemaker 
 has added two more titles. The result of all these 
 efforts has been of slight value theoretically or practi- 
 cally. The classes of Linnaeus are nicely exempli- 
 fied by certain odors, but when you attempt to 
 classify a large number of odors according to the 
 scheme, you find that many belong equally well 
 under two or more headings, and others refuse to fit 
 anywhere. The types selected evidently do not 
 represent anything fundamental. 
 
SENSATION QUALITY 63 
 
 LINNiEUS' OLFACTORY CATEGORIES. EXAMPLES 
 
 1. Aromatic Turpentine; lavendar; camphor; spices; 
 
 butyric ether. 
 
 2. Fragrant Flowers; vanilla; benzoin. 
 
 3. Ambrosiac Musk; ambergris. 
 
 4. Alliaceous Garlic; assafoetida; CI.; Br; CS^. 
 
 5. Hircine Cheese; sweat; rancid oil; lactic acid. 
 
 6. Repulsive, or 
 
 Virulent Opium; nightshade family. 
 
 7. Nauseous Decaying animal matter. 
 
 zwaardemaker's additions 
 
 a. Ethereal Fruits; some essential oils and ethers. 
 
 b. Empy rheumatic . .Toast; tobacco smoke; tar; coffee; gas- 
 
 olene; creosote. 
 
 Although the attempt at classification has been 
 a failure, some hope has been aroused by the dis- 
 covery, by Sir William Ramsay and others, that cer- 
 tain substances with similar molecular structure 
 have similar odors, and that in a group of substances 
 of similar structure (as the alcohols) the pungency of 
 the odor increases with the molecular weight. Al- 
 though there are exceptions enough to make the 
 connections merely interesting and suggestive, it 
 seems certain that in sensations of smell we come 
 closer, so to speak, to the unexperiencible matter 
 than in sensations of any other mode. 
 
 Individuals differ in their sensitiveness to odors 
 even more than they do in regard to taste. Some 
 persons are osmically as keen as the lower animals ; 
 
54 A SYSTEM OF PSYCHOLOGY 
 
 others are very obtuse to odor, and some are com- 
 pletely anosmic from birth. Catarrh, or other dis- 
 ease, may largely or completely rob the victim of 
 his sense of smell. Other details of osmic sensi- 
 tiveness will be mentioned under intensity. . 
 
 5. Visual Sensations 
 
 The nerve endings which condition the produc- 
 tion of visual sensations — the rods and cones — are 
 in the retina, the lining of the eyeball. The other 
 parts of the eye are important as means for the 
 bringing of the rays of light to bear properly on 
 those endings.^ 
 
 The fibres of the optic nerve pass from the rods 
 and cones through the midbrain beneath the hem- 
 isphere to the occipital lobes, the rearmost portions 
 of the hemispheres; and these, with the addition of 
 certain contiguous areas, constitute the visual cen- 
 tres.^ 
 
 Opposite to the pupil of the eye there is a little 
 depression in the retina, about two and one-half 
 square millimetres in area, called the fovea. While 
 not so sensitive to light as are the surrounding areas, 
 
 1 Piersol, figs. 1202, 1203, 1214, 1218, 1220, 1221, 1222, 1223; 
 Quain, figs. 45, 48, 52. 
 
 2 Piersol, fig. 1050; Howell, figs. 91, 92. 
 
SENSATION QUALITY 55 
 
 it is capable of finer discriminations; or, as we say, 
 the visual acuity is greatest here; hence, the eye is 
 commonly moved so that the image of whatever we 
 are attending to, or the most important part of that 
 image, falls on the fovea. Only after considerable 
 practice can one attend to a definite part of the field 
 of vision without automatically turning the eye to- 
 ward it so that its image falls on the fovea. The 
 fovea contains no rods, but only cones, and they 
 are here covered by a thinner layer of nervous tis- 
 sue than elsewhere, so that the light reaching them 
 is less dispersed, i, e,, is brought to a sharper focus 
 here than elsewhere on the retina. 
 
 A short distance from the fovea is the spot at 
 which the optic nerve enters the eyeball. This spot 
 is insensitive to light because there are here neither 
 rods nor cones, and is hence called the blind-spot. 
 The blind-spot does not inconvenience us in ordi- 
 nary vision because it is so situated in the retina that 
 the portion of the image which falls on the blind- 
 spot of one eye does not fall on the blind-spot of the 
 other. 
 
 We can discuss color only by reference to the 
 solar spectrum, and the student should, if possible, 
 examine the spectrum, either projected on a screen 
 or viewed through a spectroscope. Failing the 
 
56 A SYSTEM OF PSYCHOLOGY 
 
 actual spectrum, colored charts of it may be used. 
 Several such charts are published but are not chro- 
 matically true. 
 
 The prism of the spectroscope spreads out the 
 light- waves coming through a narrow slit into a di- 
 verging beam at one side of which there are long 
 waves and at the other short waves, the wave length 
 in the intermediate portions varying accordingly. 
 If now this beam of light falls on the retina through 
 proper lenses, or after being intercepted by a screen, 
 a band of colors — the "spectrum" — is formed, rang- 
 ing from the red produced by the least frequent 
 (longest) waves, through the orange, yellow, green, 
 blue, to the viblet of the most frequent (shortest) 
 rays; and as the wave length decreases continuously 
 from one end of the spectrum to the other, so the 
 red merges smoothly into the orange, the orange 
 into the yellow, and so on, through the intermedi- 
 ate hues of orange-red, red-orange, yellow-orange, 
 orange-yellow, etc. Here we have an excellent 
 example of a sensation-continuum; a series of sen- 
 sations passing one into the other without discrete 
 gradations; that is, without break. 
 
 Although there are a great number of hues in the 
 spectrum, there are only a few elementary color sen- 
 sations, and the other hues are composed of these 
 
SENSATION QUALITY 57 
 
 in diflFerent proportions. That such uniform grada- 
 tions can be produced by mixture is clearly shown 
 by mixing the light-rays from the ends of the spec- 
 trum, in which case a continuous gradation of pur- 
 ples is obtained, ranging from the spectral red to the 
 spectral violet: a series which is not in the spec- 
 trum, but which, with the spectral hues, makes the 
 total of colors within our experience. 
 
 Inspection shows that the orange is a composite 
 color involving red and yellow; that the hues be- 
 tween green and blue are really only blendings of 
 green and blue; and so the sensation-continuum 
 here is not different in kind from the series of blend- 
 ings of bitter and sweet, sweet and sour, etc., al- 
 though it is more readily displayed. We are jus- 
 tified, therefore, in assuming that there are a few 
 fundamental colors, just as there are a few tastes, 
 and that the combination of these produces all the 
 hues with which we are familiar.^ In seeking for 
 these fundamental colors we reject the orange, the 
 
 ^It is sometimes said that a "mixed'' color, e. g,, orange, 
 does not contain other colors (red and yellow, in case of 
 orange), but merely is like them, being really as simple as 
 they are. On this postulate a psychology of color has been 
 built up, but has so far not justified itself. We think it much 
 more rational to proceed on the simpler postulate, on which 
 all advance in the knowledge of color theory is actually 
 founded. 
 
58 A SYSTEM OF PSYCHOLOGY 
 
 blue-greens and green-blues, the yellow-greens and 
 green-yellows, and the extreme violet as being ap- 
 parent mixtures. We have left as presumably fun- 
 damental colors: red, yellow, green, and blue or 
 violet-blue; and these, or certain specific portions 
 of them in the spectrum, seem to be truly element- 
 ary. But in the consideration of them two peculiar 
 circumstances are at once discovered, which merit 
 careful attention. 
 
 In the first place, there is no direct qualitative 
 transition between the red and the green, and none 
 between blue and yellow. That is to say: while 
 you may arrange between red and blue a continuum 
 involving only these two colors (the red-blues or 
 purples); and between blue and green a similar 
 continuum of green-blues and blue-greens; and 
 between green and yellow a continuum of green- 
 yellows and yellow-greens; and between yellow and 
 red a continuum of yellow-orange, orange, etc., the 
 yellow-blues and the red-greens are lacking. The 
 transition in either case involves one of the other 
 supposedly elementary colors, or else white (gray). 
 We can, for example, pass from red through orange 
 and yellow, or through purple and blue, or through 
 pale red (pink), gray, and pale green; but never 
 through red-greens. Yet, if red and green are ele- 
 
SENSATION QUALITY 59 
 
 mentary colors we surely ought to be able to com- 
 bine them as well as any other pair. This at once 
 suggests that the four colors are not on the same 
 plane. 
 
 In the second place, the combination of green 
 rays and red rays in diverse proportions (as regards 
 intensities) gives the transition colors through yellow, 
 while analogous combinations of yellow and blue 
 rays produce the transition colors through white 
 
 (gray). 
 
 These relationships lead to the conclusion (first 
 formulated as a scientific theory by Thomas Young), 
 that yellow is not an elementary color, but is really 
 red-green, and that gray is the composite of the 
 three elementary colors, red, green, and blue (or 
 indigo). This is the so-called " Three-Color Theo- 
 ry," or "Young Theory'' — often called the 
 " Young-Helmholtz Theory.'' According to it, the 
 three colors are supposed to depend each on a 
 specific process in the retina and in the brain (chro- 
 moptic process) the nature of which is unassigned; 
 and each of these three processes is supposed to be 
 excited by light from all parts of the solar spectrum, 
 but most strongly from one particular region (see 
 fig. 5). The yellow portion of the spectrum is so 
 colored because the rays from that portion excite 
 
60 A SYSTEM OF PSYCHOLOGY 
 
 both the red and green processes rather strongly; 
 while the rays from the blue-green portion excite 
 both the blue and the green processes strongly. 
 
 This theory, as it has been developed by Helm- 
 holtz and others, succeeds in referring to one logical 
 scheme all the facts of visual sensation yet discov- 
 ered; but in its looser statement it has encountered 
 one serious criticism. This criticism is that yellow 
 cannot be introspectively analyzed into red and 
 green, and gray into red, green, and blue. Exam- 
 ine pure yellow as intently as you may, and you can- 
 not find any red or green in it, and gray, if it is pure, 
 is ipso facto neither reddish, greenish, nor bluish. 
 This consideration has led many physiologists and 
 psychologists to hold to the theory of Hering, or 
 to variants of his theory. They hold that there 
 are four colors — and four retinal processes, with an 
 additional process for white. They even assert that 
 black is an elementary sensation, and assign a sixth 
 retinal process to it. These six processes are in pairs, 
 the members of each pair opposing each other. 
 We cannot go into the details of this theory, 
 or the many objections to it. It is a noteworthy 
 fact that the practical working out of the theory 
 obliged its adherents to abandon the very psycho- 
 logical grounds on which they started, by assuming 
 
SENSATION QUALITY 61 
 
 as a fundamental color either blue-green or reddish- 
 purple/ 
 
 The three-color theory, as first proposed, implied 
 the composite nature of the sensations of white and 
 gray, and assumed that a "color-blind" (see below) 
 person lacked one or two of the three processes. As 
 a matter of fact, the first point is not essential to 
 the theory; for all that is necessarily assumed is 
 that when the "red'' process and the "green'' proc- 
 ess are active together at certain relative intensities, 
 the sense-content yellow arises. So, the theory need 
 not insist on white as a complex, but may allow 
 the alternative opinion. That is to say; the three- 
 color theory is not necessarily a three-sensation 
 theorv. 
 
 In behalf of the three-sensation theory, however, 
 it must be said that the fact that a content of ex- 
 perience cannot be directly analyzed does not prove 
 it to be simple. Of course we may assume such to 
 be the case, and a certain sort of psychology does 
 make that assumption to cover certain convenient 
 cases. If the assumption were applied in a thor- 
 ough-going way it would make psychological analy- 
 
 ^ For further details of the Hering theory see Rivers, 
 (Schafer), pp. 1112-1121. On the Young theory, idem, 
 1106-1112. 
 
62 A SYSTEM OF PSYCHOLOGY 
 
 sis impertinent, to say the least, and experimental 
 psychology is based on the denial of this assumption. 
 As for color-blindness, whatever the earlier ad- 
 herents of the theory may have held, the present 
 adherents hold that in the common cases of color 
 abnormality the three processes are present, but 
 have an unusual range of excitability, as will be 
 explained later, although it may be that in some 
 cases there may be one or more of the processes 
 lacking.^ 
 
 6. The Schematic Representation of Visual Qualities 
 
 The whole range of color hues may be repre- 
 sented (as they might actually be presented) in the 
 following way. Suppose three circular patches of 
 light partially superposed as in fig. 1. Let one 
 patch of light be of each of the three fundamental 
 colors, and let the intensity of each patch be maxi- 
 mal at its centre, falling off gradually to zero at the 
 edge. We have then in the triangle of which N is 
 the centre (leaving now out of account all the un- 
 
 ^The three-color theory in the five-sensation form has been 
 given an evolutionary setting by Mrs. Franklin, who assumes 
 that gray is the primitive color phylogenetically; that in the 
 second stage of development yellow and blue arise by a dif- 
 ferentiation of the "gray-process'^ into two new processes, 
 and that in the third stage red and green arise by a differ- 
 entiation of the "yellow-process." 
 
SENSATION QUALITY 63 
 
 superposed and two-ply parts) all the colors, rang- 
 ing from the full hues along the boundaries, through 
 paler tints, to neutral gray or white near the centre. 
 This representation introduces us at once to a 
 characteristic of color sensations which is desig- 
 nated saturation, A color is said to be saturated in 
 
 Fig. 1. Fig. 2. 
 
 proportion as it does not contain white or gray; the 
 more gray the color contains (that is, the paler it is), 
 the less the saturation is said to be. 
 
 If we suppose the three fundamental colors to be 
 taken in their maximal saturation, we can represent 
 all visible hues in every possible saturation by such 
 a triangle as that in fig. 1, in which the pure funda- 
 mentals stand at the vertices. For convenience we 
 draw the sides of the triangle straight, as in fig. 2; 
 but it must be understood that the exact form of the 
 triangle is insignificant — the fact that we have 
 drawn it isosceles does not imply that the difference 
 
64 
 
 A SYSTEM OF PSYCHOLOGY 
 
 between R and G is equal to that between R and B, 
 etc., for these differences are incommensurable. 
 We might, indeed, use a circle in place of a triangle, 
 locating the fundamental colors thereon at appro- 
 priate points; and this "color circle" is frequently 
 employed in preference to the "color triangle/' 
 
 Fig. 3. 
 
 Fig. 4. 
 
 Now, we may wish to represent different inten- 
 sities of color; this we may do in the dimension at 
 right angles to the plane of the " color triangle.'' If 
 we wish to represent another complete series of hues 
 at an intensity uniformly higher than those just sup- 
 posed to be represented by the triangle, we do it by 
 a second triangle above and parallel to the first, 
 as in fig. 3. In ttiis connection we find the peculiar 
 fact that if we start with that intensity of a pure 
 spectral light which gives the maximal saturation, 
 and steadily increase the intensity, the saturation of 
 the sensation soon begins to decrease, and at a cer- 
 
SENSATION QUALITY 65 
 
 tain high intensity of the stimulus the color becomes 
 white. Schematically, this would mean that the 
 triangles must be drawn smaller and smaller, as we 
 go up, until they become points. In decreasing the 
 intensity the same phenomenon is met; all colors 
 becoming gray (red is possibly an exception) before 
 being extinguished; the saturation-decrease being 
 more sudden at this end. 
 
 The quahtative changes perceived as a light stimu- 
 lus of practically homogeneous wave length is pro- 
 gressively increased from zero to a maximum, are 
 shown schematically in fig. 4. The line w pz is the 
 series of grays, or neutral sensations, and is, there- 
 fore, conceived as perpendicular to the color tri- 
 angle (or color circle) at the centre. 
 
 The interval z k, in which the stimulus arouses 
 only the sensation of gray; the interval, therefore, 
 between the light-threshold and the color-threshold, 
 is called the photochromatic interval. Logically, 
 there is an upper photochromatic interval also, but 
 it is not susceptible of measurement because of the 
 incident damage to the eye. 
 
 Since the rate and the magnitude of change are 
 represented here purely schematically, we may rep- 
 resent any hue by a curve of the same form. Rang- 
 ing them all around the common gray-axis, we 
 
66 A SYSTEM OF PSYCHOLOGY 
 
 derive (i, e., by rotating fig. 4 on the axis iv p z) an 
 onion-like figure, which, taken as a solid, contains 
 schematically all possible visual sensations.^ Linear 
 distance parallel with the axis represents intensity- 
 change; linear distance perpendicular to the axis 
 represents saturation change; and angular distance 
 about the axis represents change of hue. 
 
 Since white (gray) is equivalent to a certain pro- 
 portion of red, green, and blue, it is evident from 
 the color triangle that, for any color, we can find 
 another color which when mixed with it will pro- 
 duce gray, provided the intensities of the two are 
 properly chosen; for all points on the triangle (ex- 
 cept the vertices) represent combinations of two of 
 the fundamental colors: and to any combination of 
 two it is possible to add one of them and the third in 
 such proportions that the proportions of the three 
 shall be whatever is desired. And practically the 
 conditions are quite easy of fulfilment. Colors 
 which combine thus in pairs to produce gray are 
 called complementary. Examples of complement- 
 ary colors are: red and a certain blue-green; or- 
 
 ^ This is the tri-dimensional figure on the basis of the color 
 circle. It might be constructed on the basis of the triangle, 
 only the description of the generation is a little more difficult. 
 Commonly, the line z mw, of fig. 4, is made a semicircle or else 
 two straight lines, from m to w and m to z. The solid figures 
 become then a sphere or a double pyramid or a double cone. 
 
SENSATION QUALITY 67 
 
 ange and greenish-blue: yellow and indigo-blue; 
 green and reddish-purple. 
 
 We have used the terms white and gray inter- 
 changeably. White is a relative term denoting the 
 brightest gray. Any piece of paper which looks 
 "white" may, if placed on a still whiter one be 
 made to be a dull gray; and the new "white" may 
 be literally put in the shade by a still brighter. 
 "Black," too, is purely relative. The blackest 
 paper obtainable looks dark gray against a black 
 velvet. Black and white are contents of conscious- 
 ness, but not sensations simply; they are complex 
 sensations of gray perceived in certain relations. 
 The difference between the various neutral grays 
 is one of brightness only, that is, they form an in- 
 tensive series of identical quality (whether we con- 
 sider it a simple quality, or a mixture of three). 
 
 7. Achromopsia and Parachromopsia 
 
 Individuals differ in the sensitiveness of their 
 color processes to the action of light of various wave 
 lengths, and in the cases of some persons the varia- 
 tion from the normal is so considerable that these 
 persons are called color-blind. In extreme cases the 
 patient can see no color at all, everything appearing 
 to him gray; so that the landscape which shows 
 
68 A SYSTEM OF PSYCHOLOGY 
 
 to US a wealth of hues presents itself to him as a 
 black and white sketch. Yet the color-blind man 
 may not realize that his vision is different from yours, 
 and if you ask him the color of the grass he will say 
 ''green/' for he has always heard it called so, and 
 has no way of knowing that "green" does not mean 
 to you the same particular shade of gray it does for 
 him. Such a person is said to be totally color-blind, 
 or achromopsic. 
 
 More numerous than the ''achromopes'' are per- 
 sons who see colors, but not as we see them; they 
 are called partially color-blind, or par achromopsic; 
 parachromopes. The commonest case is that in 
 which only blue and yellow are seen (in addition to 
 gray), the normal red and green of the spectrum 
 appearing yellow and a certain part of the blue-green 
 appearing gray, as does also a certain purple (not 
 in the spectrum, of course, but mixed from blue and 
 red), which is to the normal eye complimentary to 
 this blue-green. This is a typical sort of dichro- 
 mopsia (two-color vision). Other persons see some 
 green in addition to the gray, yellow, and blue; 
 others probably see gray, red, and one other color; 
 and still others see only gray and one color, which 
 is probably green in some cases. 
 
 How large the list of color abnormalities in vision 
 
SENSATION QUALITY 69 
 
 — parachromopsias — may be, we cannot even guess, 
 as yet, but enough is known to assure us that it is 
 not small. The detection of these abnormalities is 
 of great importance for railroad and nautical pur- 
 poses, but is difficult, and possible only by skilfully 
 arranged tests. Exact work can be done with spec- 
 tral light and elaborate apparatus, but rough tests 
 can be made with colored worsteds or silks. A few 
 cases have been found in which the patient had one 
 eye achromopsic, or parachromopsic, and the other 
 normal, or nearly so, so that he could tell just what 
 colors were seen with the defective eye; and these 
 cases have given indispensible assistance in diag- 
 nosing the color defects of others. 
 
 We must distinguish between true parachromop- 
 sia and mere lack of memory for hues, or inability 
 to name them properly, or awkwardness in sorting 
 them. While it is true that a genuine defect may 
 escape detection sometimes, it is also true that a 
 person may fail miserably in a color test, and yet be 
 chromopsically normal, just as a nervous patient 
 may, by confused reports on the oculist's tests, be 
 convicted of serious astigmatism, and yet not be 
 astigmatic at all. It is said that there are more 
 color-defective men than women, but this may be 
 doubted. Women are much more apt to escape 
 
70 
 
 A SYSTEM OF PSYCHOLOGY 
 
 detection, even by themselves, because of more prac- 
 tice in handling colors. 
 
 The totally color-blind person is apt to be able to 
 see in a dim light better than a normal person, and 
 
 to find unbearable a light which is for the normal 
 person reasonably strong. This suggests at once 
 the possibility that all three color-processes are 
 present in his eye, and that they are alike excitable 
 by rays of light of any wave length included in the 
 spectrum. This hypothesis is also necessitated by 
 
SENSATION QUALITY 
 
 71 
 
 the fact that in cases of monocular achromopsia 
 gray is seen aUke by both eyes. This condition is 
 represented by the curves in fig. 8, where the achro- 
 
 FiG. 8. 
 
 mopsia is nearly complete; if complete the three 
 curves would exactly coincide throughout. Fig. 5 
 gives the probable relations of excitability of the 
 three processes in the normal eye, showing how 
 each color is excited by practically all rays of the 
 
72 A SYSTEM OF PSYCHOLOGY 
 
 spectrum, but principally in a certain range. In 
 these and the following curves the horizontal axis 
 represents the spectrum, and the ordinate at any 
 point represents the relative degree of excitation of 
 the process by the light from that point in the spec- 
 trum. The curves are not intended to represent 
 any specific ratios, only the general positions being 
 in point. Exact forms for the curves have been com- 
 puted by several theorizers, but such computations 
 are, after all, of little value, since they represent the 
 carrying out of the results of certain postulates. 
 
 Curves I, II, and III, in fig. 5, show the probable 
 relative excitability of the red, green and blue proc- 
 esses respectively, for the normal eye. Curve IV 
 represents the relative brightness of the different 
 parts of the spectrum as determined by the flicker 
 method. Curves I, II, and III are so drawn that 
 the sum of their ordinates at any point on the spec- 
 trum (X-axis) is equal to the ordinate of curve 
 IV at that point. 
 
 Curves I, II, and III in figs. 6, 7, and 8 are ar- 
 bitrarily modified from the curves in fig. 5, so that 
 they may represent the color-vision abnormalities 
 described. Curve IV in these figures is, accordingly, 
 derived by summing the ordinates of curves I, II, 
 and III. 
 
SENSATION QUALITY 73 
 
 Fig. 6 shows the probable excitability of one type 
 of yellow-blue parachromopsia (red-green blind- 
 ness), in which the spectrum is of practically normal 
 length. This was formerly supposed to be "green- 
 blindness" and is often designated by the term 
 "proteranopia." Fig. 7 represents the excitability 
 in another type of yellow-blue parachromopsia, 
 where the spectrum is shortened; formerly called 
 "red-blindness"; "deuteranopia." There are all 
 sorts of parachromopsias intermediate between these 
 two, constituting, as we said before, the more numer- 
 ous sorts of color-blindnesses. Other abnormalities 
 than "yellow-blue" vision are known to exist, and 
 may be represented by proper modification of the 
 curves.^ 
 
 The normal eye is not equally sensitiye to Hght 
 
 ^ The tri-chrome theory must not be understood as an 
 explanation of the facts of "color-blindness," or of the other 
 complex phenomena of color vision. It is merely a compre- 
 hensive statement of all the facts; a descriptive theory, in 
 short. It is not the only possible statement, but has the vir- 
 tue of being the simplest. We can, for example (contrary, 
 it is true, to general opinion), give just as thorough a state- 
 ment with red, yellow, and blue as the fundamental colors, 
 and work it out logically to cover all the known facts; but 
 it would be more complicated. A slightly less complicated 
 theory than this might be constructed with four fundamental 
 processes and colors — it is all a matter of drawing the curves 
 for the normal spectrum. Still other possibilities are open, 
 but for the present it seems best to rest on the simplest state- 
 ment. 
 
74 A SYSTEM OF PSYCHOLOGY 
 
 and color In all parts. At the centre of the retina 
 colors are discriminated with the greatest ease, but 
 as you go out toward the edge of the visual field 
 discrimination becomes more diflScult, and the col- 
 ors lose in saturation until at the extreme limit of 
 visibility they are practically all gray. It is some- 
 times said that the margin of the retina is totally 
 color-blind, and the zone intermediate between the 
 margin and a certain central area, red-green blind. 
 This is only partly true. The angular distance 
 from the centre to which any color can be carried, 
 and yet be visible in its proper hue, depends on 
 practice, intensity, area, and duration. With intense 
 spectral light, lasting but an instant, the colors can, 
 after considerable practice, be discriminated nearly 
 to the periphery. 
 
 8. Color Adaption and Contrast 
 
 Protective adaptation is especially noticeable in 
 the visual realm, but takes several forms. In addi- 
 tion to the control of the stimulus by the iris and 
 of the sensitivity of the nerve-endings by the retinal 
 pigment, there are adaptive changes which go on 
 either in the retina or in the brain, by virtue of 
 which any stimulus tends to produce a sensation 
 which becomes more and more gray as the stimu- 
 
SENSATION QUALITY 75 
 
 lation continues. The most familiar example of 
 this phenomenon is found in yellow lamplight, 
 which soon loses its yellowness if we are under its 
 illumination exclusively. The change is also rapid 
 in lights which are yellow-green, bluish-green, or 
 purple; blue changes less rapidly, and red very 
 slowly. The change is not essentially connected 
 with loss of total intensity, and so is not to be con- 
 fused with fatigue. 
 
 In terms of the tri-chrome theory, color adapta- 
 tion is a decrease in sensitiveness of processes 
 strongly stimulated, with increase in sensitiveness of 
 processes feebly stimulated. If, for instance, blue- 
 green light is cast on the retina, the blue process and 
 the green process are strongly excited, the red proc- 
 ess hardly at all; the result is a sensation com- 
 plex in which blue and green predominate. As 
 the light continues to act, the blue and the green 
 processes respond progressively less and less, 
 and the red process more and more, so that the 
 sensation complex becomes less and less satu- 
 rated. 
 
 The results of these adaptative changes are clearly 
 shown when colorless (gray) light, e, g,, from a gray 
 wall or paper in ordinary daylight, is allowed to fall 
 on the part of the retina previously stimulated by 
 
76 A SYSTEM OF PSYCHOLOGY 
 
 the colored light. Under these conditions the proc- 
 ess or processes that have increased in sensitivity 
 respond more intensely than the process or proc- 
 esses that have decreased, and the result is a tinge 
 of the color complementary to the original color. 
 This color effect occupies the exact retinal area 
 occupied by the exciting color, and its appearance 
 is known as the negative after-image} 
 
 The quahty of a light is determined, in the case 
 just mentioned, by the intensive relations of the 
 physio-psychological color components. In all cases 
 the hue of the sensation roused by any given stim- 
 ulus is a variable affair, depending on the condi- 
 tion of the portion of the retina on which the stim- 
 ulus falls, and on the condition of the adjacent 
 retinal areas. The latter factor determines what is 
 known as color contrast, or, to distinguish it surely 
 from the after-image effect, simultaneous contrast. 
 If you look at a small gray card placed on a large 
 colored surface, you get the contrast effect very 
 clearly: the card will appear tinged with the color 
 complementary to that of the background. The 
 
 ^ Adaptation may take place, and be followed by the 
 characteristic negative after-image, without any sensation of 
 color during adaptation being noticed. This may be demon- 
 strated by placing the subject in colorless light, to which 
 minute amounts of a color are continuously added. 
 
SENSATION QUALITY 77 
 
 eyes must not move during this observation, but 
 must remain steadily fixed, or after-images will 
 occur, and counterfeit the effect; slight movements 
 will unavoidably occur, giving rise to narrow after- 
 image effects along the edges of the card; so-called 
 edge-contrast. The saturation of the contrast-color 
 may be increased by covering the card and back- 
 ground with a piece of tissue-paper or ground glass; 
 by squinting through the nearly closed lids; or by. 
 darkening the room (as by pulling down the win- 
 dow-shades). No matter what the brightness and 
 saturation of the colored background, or the bright- 
 ness of the gray, one of these changes will heighten 
 the contrast-color. 
 
 No satisfactory explanation of the contrast effect 
 has as yet been found, but the most plausible theory 
 is that substances essential to the processes in the 
 retinal area stimulated by the colored rays are 
 drawn from the area stimulated by the gray, leav- 
 ing that area, therefore, more sensitive to the other 
 rays of the spectrum, because relatively better sup- 
 plied with substances reacting to those rays. Of 
 course the basis for this phenomenon, as well as for 
 that of after-images, may not be in the retina, but 
 may be in the brain; there is absolutely no means 
 of deciding at present between the two possibilities, 
 
78 A SYSTEM OF PSYCHOLOGY 
 
 but the fashion is to suppose that the retinal hy- 
 pothesis is the true one. 
 
 An interesting experiment which possibly demon- 
 strates the transfer of photochemical substance 
 across the retina, may be performed with an '' Archi- 
 medean spiral," in black and white, on a pasteboard 
 disk; this is supplied in the Miinsterberg set of il- 
 lusions (by the Milton Bradley Co.). If the disk 
 is rotated steadily — a clock-work or electric motor 
 with controllable speed is best, but a hand-power 
 color-mixer will do — at such a rate that when the 
 eyes are fixed on the centre, rings run outward, 
 like those from a stone dropped in the water; if 
 these rings are observed several seconds (the eyes 
 not moving), and if the eyes are then quickly closed 
 and covered with a large piece of black cloth, 
 "retinal streaming'^ will be observed, the bright 
 streamers running from edge to centre of the dark 
 field. If the disk is rotated in the opposite direc- 
 tion, so that the rings run toward the centre, the 
 streaming will be from the centre out. The closing 
 and covering of the eyes must be very. quickly done; 
 the cloth being held on the palms of the outspread 
 hands ready for action while observing the rings. 
 After some practice the streaming can be observed 
 by simply closing the eyes, without covering. A 
 
SENSATION QUALITY 79 
 
 more striking method is to have a single source of 
 Hght, which illuminates the disk brightly, and to 
 cut this light off at the proper moment, leaving the 
 room in total darkness. Turning out an electric 
 light will not do, as the light dies too slowly. 
 
 The streaming may be observed on the disk itself 
 while it is in rotation; it is in the direction of move- 
 ment of the rings, and gives them a peculiar wavy 
 appearance. On looking suddenly at some other 
 object, the streaming in the reverse direction makes 
 the object seem to expand or shrivel up in an odd 
 way. 
 
 If we assume a definite "color substance ^^ in the 
 retina corresponding to each of the three hypotheti- 
 cal color processes, . then it is a natural step to as- 
 sume that these substances are attracted to the re- 
 gion stimulated by the white rings, and so drawn 
 outward (or inward) with the rings. This is ren- 
 dered still more probable by the occurrence of what 
 are known as "Fechner's colors"; as you look at 
 the disk, it will sometimes take on a red or green 
 cast; other colors occur seldom. This can be ex- 
 plained by stronger attraction for one of the sub- 
 stances, when the rate of rotation of the disk is such 
 that following rings coincide with the greatest con- 
 centrations of one of the substances. 
 
80 A SYSTEM OF PSYCHOLOGY 
 
 9. Auditory Sensations 
 
 The nerve endings of the acoustical apparatus 
 are in the cochlea of the ear/ and the cortical cen- 
 tre is in the superior temporal convolution.^ The 
 acoustical stimulus is a vibratory movement of the 
 air/ which is communicated through the external 
 auditory meatus to the middle ear (tympanum), and 
 thence through two windows (fenestra ovalis and 
 fenestra rotunda) in the bony wall to the vestibule 
 and cochlea. It was formerly supposed that the 
 little bones (ossicles) transmitted the vibration from 
 the tympanic membrane to the oval window into 
 which the head of the stirrup bone is fitted, it being 
 thought to act like a piston; but the discovery of 
 individuals whose ossicles have been destroyed, and 
 who hear nearly as well as normal persons has 
 ruined this theory. It is probable that the air of 
 the tympanum conducts the sound, and the bones 
 act as a damper. Vibrations may be carried to the 
 
 1 Piersol, figs. 1242, 1247, 1248, 1251, 1252, 1255, 1256, 
 1257, 1259, 1260, 1264, 1268, 1271, 1272, 1273; Quain, III, 
 pt. Ill, figs. 78, 87, 102, 108, 111, 113, 129, 131, 135, 136. 
 
 2 Piersol, figs. 1042, 1043, 1071; HoweU, figs. 93, 94; 
 Schafer, fig. 351. 
 
 3 Hallock (Duff), pp. 301-307; Zahm, pp. 21-53; M'Ken- 
 drick and Gray (Schafer), pp. 1149-1168; Howell, pp. 371- 
 375. 
 
SENSATION QUALITY 81 
 
 middle ear through the bones of the skull, and so 
 reach the inner ear. You may test this by touch- 
 ing the head to any object emitting feeble vibrations, 
 as a tuning-fork, violin, or piano, faintly sounding. 
 
 The exact manner in which the direct excitation 
 of the auditory nerve endings (hair-cells on the 
 basilar membrane) occurs has been the subject of 
 much speculation. The Helmholtz "piano-string" 
 theory was formerly held to be a satisfactory expla- 
 nation, and, indeed, it is in accord with many of the 
 psychological and pathological facts of audition; 
 but, nevertheless, the anatomical details of the coch- 
 lea are now believed to be against that hypothesis. 
 Helmholtz supposed elements in the basilar mem- 
 brane free to vibrate selectively to the rates of move- 
 ment to which they were adapted, and by their 
 vibration to excite the contiguous hair cells. The 
 vibration rates to which these elements were sup- 
 posed to be "tuned" increased progressively from 
 the apex of the cochlea to the "lower" end of the 
 membrane; thus the series of perceptible pitches 
 corresponded to the series of hair cells and vibra- 
 tory elements functionally connected with them.^ 
 
 The latest investigations point to the excitation of 
 
 ^ For details on the Helmholtz Theory, see Howell, pp. 
 376-379; M'Kendrick (Schafer), pp. 1171-1185. 
 
82 A SYSTEM OF PSYCHOLOGY 
 
 the hair cells by the movements of the tectorial 
 membrane: Beyond this, we are still in the realm 
 of speculation. A number of theories have been 
 elaborated in addition to that of Helmholtz, and 
 two of them seem to be worthy of entertainment. 
 These we may call briefly the telephone theory, 
 and the extensity theory. 
 
 The telephone theory antedates Helmholtz's, 
 but has been recently revived in modified forms. 
 Briefly, it holds that pitch is conditioned solely by 
 the frequency of the nervous impulses transmitted 
 to the brain — the pitch-characteristic being thus 
 supposed to be a product of the brain cells. Now, 
 whatever the exact mechanism for transforming the 
 vibratory impulses transmitted to the inner ear into 
 hair-cell stimulations, the apparatus highly sensi- 
 tive to one rate will not be so sensitive to other rates. 
 Hence the need for a series of such apparatus (which 
 is furnished in the cochlear structures) that will 
 give the maximal sensitivity to a great range of 
 vibration rates. This is mechanically the most 
 rational of all the theories; it also has the advan- 
 tage of explaining the pathological phenomena, and 
 many other details, on practically the same simple 
 grounds as does the Helmholtz theory, while not 
 open to the objections to the latter. 
 
SENSATION QUALITY 83 
 
 The extensity theory is less happy mechanically, 
 but more strictly in accord with the psychological 
 facts. Moreover, it does not turn the whole matter 
 of pitch over to unidentified brain activity, but puts 
 it on a basis where auditory sensation is strictly 
 comparable with other sensations. This theory 
 holds that the frequency of the vibration deter- 
 mines the length of the series of hair cells (measured 
 from the vestibular end of the total series) stimu- 
 lated by a given tone. The slower the vibration, 
 the more cells stimulated. Below a certain rate, 
 all the nerve endings are stimulated; above a cer- 
 tain rate, none. 
 
 So far as we can discover there is but one ele- 
 mentary auditory quality. It is customary to speak 
 of pitch as quality, but that is an unjustifiable use 
 of the word, for the difference between red and 
 blue is not at all of the same sort as the difference 
 between a low and a high note, although physically 
 they both correspond to a difference of vibration 
 rate. 
 
 It is true that as notes are sounded they differ in 
 a respect other than pitch, which again is com- 
 monly called quality. The note of the violin, when 
 of the same pitch as the note of the flute, is readily 
 distinguishable from it. Low and high notes of the 
 
84 A SYSTEM OF PSYCHOLOGY 
 
 same instrument differ more or less in the same 
 way. This difference is one of complexity and 
 intensity of components, and in strict discourse 
 should not be called qualitative. The best word 
 available for this quasi-character of tones is timbre. 
 The Helmholtz theory of audition makes pitch 
 analogous to local sign of touch and sight. The 
 "telephone theory'' might assign a strictly quali- 
 tative nature to pitch, although acceptance of the 
 theory does not necessarily commit one to the 
 qualitative view. On purely psychological grounds, 
 pitch is analogous to extensity of visual and tactual 
 sensation and we shall, therefore, treat it further 
 under the head of extensity. 
 
 10. Cutaneous and Subcutaneous Sensations 
 
 Scattered through the skin, and the tissues im- 
 mediately beneath it, the mucus membrane, the 
 peritoneum of the abdominal cavity, the tissues 
 adjacent to the apposed joint-surfaces, and in the 
 muscles, tendons, and bones themselves, there are 
 numerous sensory nerve endings, of a wide range 
 of complexity, which respond to mechanical stim- 
 ulation and to temperature changes. The joint, 
 muscle, and tendon endings we will discuss in the 
 next section, treating here only those in and im- 
 
SENSATION QUALITY 85 
 
 mediately beneath the superficial coverings and 
 linings. 
 
 The simplest of these organs are no more than 
 slight knobs on the ends of nerve fibres, in contact 
 with cells of the tissues in which they are placed. 
 A development from the knob is a little disk, or 
 concave plate, in contact with a cell as the cup with 
 an acorn. In a third form, the nerve ending is be- 
 tween two specialized cells. In higher forms there 
 are several knobs, or platelets, on branches of the 
 nerve fibre, or fibres, which are enclosed within 
 special cells or structures. The most complicated 
 organs contain networks or "skeins" of nerve fibres 
 of great intricacy . 
 
 As these differeiit sorts of nerve endings were dis- 
 covered they were given the names of their dis- 
 coverers. Thus there are "end-bulbs of Krause,'^ 
 "Pacinian corpuscles," "plume-organs of Ruifini" 
 and so on. As more types are discovered, and as 
 they are found to form a series in increasing com- 
 plexity, these names become of less importance 
 except to the anatomist.^ 
 
 The cortical centres for cutaneous sensation are 
 
 ^For dermal and sub-dermal structures and organs see 
 Piersol; figs. 867 to 875, and 1146 to 1148; Quain, figs. 389 
 to 398, 402, 403, 407, 408. 
 
86 A SYSTEM OF PSYCHOLOGY 
 
 variously located by different physiologists. The 
 most probable theory is that they are near the 
 "motor zone/' on the anterior side of the fissure of 
 Rolando.^ This statement holds also for the sim- 
 ilar sensations from the mucus membrane, and 
 from the subcutaneous tissues. For convenience, 
 and in accordance with established custom, we will 
 refer to these all as " cutaneous '' except where we 
 make specific distinction. 
 
 The qualities of cutaneous sensation are fairly dis- 
 tinct. Touch, tickle, warmth, and cold, are easily 
 discriminated. Pressure is possibly of a different 
 quality from touch. Pain is commonly considered 
 as a specific quality of sensation, but of that we will 
 speak below. 
 
 Touch is aroused by light mechanical stimulation 
 of the skin (or of the mucus membrane, etc.). It 
 may also be aroused by electrical stimulation, by 
 radiant heat, or (on the mucus membrane) by the 
 action of certain substances denoted as "astrin- 
 gent." Tickle is aroused by a lighter stimulation, 
 and pre-eminently if the stimulus is of the stroking 
 sort. It is practically impossible to arouse tickle 
 without in some degree arousing touch also, and 
 light touches are very apt to give gargalic sensation 
 ^ Piersol, figs. 1041-1043. 
 
SENSATION QUALITY 87 
 
 along with the tactual; nevertheless, the two sen- 
 sation-qualities are so distinct that they are unmis- 
 takably discriminated. They are also strongly 
 distinguished in respect to intensity of stimulus and 
 motor response. A very light stimulation will 
 arouse a powerful tickle sensation, and the impulse 
 to move the hand to the spot tickled, or to move the 
 tickled member, is usually irresistible. The develop- 
 ment of this strong reflex through the necessity 
 of guarding against insects has often been conject- 
 ured. If the stimulation is increased in intensity, 
 the sensation of touch replaces that of tickle, and 
 the sensation intensity is much reduced, as is also 
 the strength of the reaction-impulse. 
 
 The production of tickle sensation usually in- 
 volves also the production of organic processes and 
 sensations in addition to the specific reflex. This 
 general bodily disturbance, which doubtless has its 
 function in the acceleration and intensification of 
 the reaction, is commonly known as tickle, or tick- 
 lishness; but this we are not discussing here. We 
 are referring to the quality of the superficial sensa- 
 tion alone. 
 
 Pressure, as we use the term (usage in regard to 
 "touch'' and "pressure'' varies very much) is 
 aroused from organs deeper than the skin; or at 
 
88 A SYSTEM OF PSYCHOLOGY 
 
 least it is aroused by physical pressure heavier than 
 is required to arouse touch. It may be of the 
 same quality, nevertheless; inspection shows in it 
 nothing certainly different from intense tactual 
 sensation free from the gargalic; and common usage 
 treats touch and pressure as one. 
 
 Warmth and cold are distinct qualities, although 
 dependent on variations in the same physical tem- 
 perature continuum. In this respect they are perhaps 
 analogous to touch and tickle. The conditions for 
 the arousal of warmth and cold are complex, and 
 as yet not well understood. When the skin has 
 been maintained at a certain temperature for a 
 short time it usually ceases to respond to that ther- 
 mic condition with either rhigotic or thalpotic sen- 
 sation. This temperature is, therefore, called the 
 neutral point for that portion of the skin at that 
 particular time. If now the skin is subjected to 
 temperature conditions above this neutral point, the 
 nerve endings are so stimulated that warmth sen- 
 sations occur; conversely, if the skin is subjected 
 to a temperature below the point of neutrality, pro 
 tempore, cold is felt; the sensation persisting in 
 either case until a new neutral point is established. 
 There are, however, cases which this formulation 
 does not seem to fit, and a formulation in terms 
 
SENSATION QUALITY 89 
 
 of a temperature-zero has been attempted. When 
 the temperature of the skin is above this zero (it is 
 supposed) warmth sensations are aroused; when 
 below, cold. This theory may be stated adequately 
 as follows: When we feel cold (or warm) the tem- 
 perature of the skin is below (or above) a temperature 
 at which — under conditions otherwise the same — 
 we would feel neither warmth nor cold. This may 
 be true, but it doesnH seem to help much.^ 
 
 As the temperature of the body varies in differ- 
 ent regions, objects which feel warm to one part 
 
 * Perhaps the safest hypothesis is that the nerve endings 
 adjust themselves to a rate of heat-radiation from the skin, 
 if that rate lies within a certain range, and is maintained for 
 a certain length of time, so that they are not stimulated. If, 
 now, the rate is suddenly changed, stimulation of the appro- 
 priate end-organs takes place and continues until the organs 
 adapt themselves to the new rate. If the change is made 
 gradually the protective adaptation may take place with 
 very little, or practically no, sensation as in the case of color 
 adaptation. Thus, if the hand is placed in water which feels 
 "neutral," and held still while the temperature of the water 
 is slowly raised or lowered, the water may be heated or cooled 
 to a point which would normally feel hot or cold to the hand, 
 yet in this case no sensations be aroused. I have seen a pa- 
 tient's hand which was kept in warm water for several hours 
 for the treatment of an abscess. The water became slowly 
 hotter, and so scalded the hand that the skin came off over the 
 whole surface, yet the patient f oimd the water only comfort- 
 ably hot. Frogs have been frozen stiff, or boiled to death, 
 while making no efforts to escape or giving other signs of dis- 
 comfort; the water. in which the animal was placed being 
 changed in temperature very slowly. It is true that these 
 last illustrations bear more specifically on the so-called pain 
 sense; but see text. 
 
90 A SYSTEM OF PSYCHOLOGY 
 
 mav feel cool to another. The cold and warmth 
 processes may be aroused by agents other than 
 temperature changes; pepper, for instance, arouses 
 warmth. Or, if these "warm*^ substances do not 
 directly excite the nerve endings, they at least lower 
 the neutral point. 
 
 It has been alleged that heat is a combination of 
 the warmth and cold qualities, and certain experi- 
 ments seem to support this view. The significance 
 of the experimental results is, however, a matter of 
 doubt, and there is as yet no suflBcient reason for 
 considering "heat" as other than an intense and 
 perhaps "painful" warmth sensation.^ 
 
 Pain is often listed as a specific quality of sensa- 
 tion. This usage arises in part from considera- 
 tion of the topographic distribution of cutaneous 
 sensation (see below) and in part from imperfect 
 analysis. The use of the word pain in this connec- 
 tion is due to a confusion of the pricking or stinging 
 quality of the sensation aroused by the stick of a 
 needle with the powerful unpleasantness which often 
 
 ^ The impulse to the interpretation of heat as warmth j)lus 
 cold comes /doubtless, from certain analogies, between warmth 
 and red, and cold and green. We usually term the reds 
 "warm" colors, and greens " cold/' If heat were a combina- 
 tion, either psychologically or physiologically, of warm and 
 cold, it would be analogous to yellow. The next step would 
 be to analogize touch to blue, and pain to white. 
 
SENSATION QUALITY 91 
 
 characterizes such sensations. By sticking the hand 
 with the needle carefully, so that the sensation is 
 not unpleasant, the same quality can be aroused, 
 and then seems to be no other than a small, intense 
 heat sensation, chiefly distinguished from a true 
 heat sensation by not being accompanied by sensa- 
 tions of warmth (less intense heat) from adjacent 
 localities and by being smaller than the heat ex- 
 tensity. By these differences, and possibly by dif- 
 ferences in the time relations — the rapidity of de- 
 velopment and fading of sensations — we are usually 
 able to distinguish the sensation from a heat stim- 
 ulus, from that of a sticking or cutting stimulus. 
 Sometimes, however, we are misled and may feel 
 a prick as a burn, or vice versa. 
 
 Itch is usually a combination of tickle with 
 warmth or heat. Often the warmth has scattered 
 points of relatively high intensity — prickling — which 
 makes the itch highly unpleasant. Rubbing the 
 itching areas relieves the situation by temporarily 
 annulling the tickle. 
 
 Ache, such as may be aroused by plunging the 
 hands in ice- water, is not a cutaneous sensation, and 
 is capable of being aroused generally throughout the 
 organism. We shall speak of it under organic sen- 
 sation. 
 
92 A SYSTEM OF PSYCHOLOGY 
 
 Not all of the dermal sensations are to be aroused 
 readily from any point of the skin. If you move a 
 cool or warm metal stylus lightly and carefully over 
 the skin, you will find that only at certain points is 
 the thalpotic or rhigotic sensation produced, unless 
 between these points the stylus is allowed to rest 
 long enough for heat to be transmitted laterally. 
 You may mark these points where the sensation 
 appears directly with small ink spots (one color for 
 the spot stimulated by the warm stylus and another 
 for that stimulated by the cold) ; then you may test 
 for "pressure points" with a thin bristle, and "pain 
 points" with a fine needle. You will find that many 
 points in the skin may be penetrated painlessly, and 
 on many the pressure of the bristle will not be felt, 
 if the bristle is not too stiff, You make a chart on 
 the skin of the points which are sensitive, and if the 
 marks are made with indelible ink you may find 
 that on following days the same points will respond, 
 and the ones which did not respond continue in- 
 sensitive, if the degree of stimulation is the same. 
 
 A great deal has been made of this topographical 
 distribution of sensation, since it was discovered, 
 thirty years ago. It was at first supposed that the 
 points indicated the locations of specific end-or- 
 gans, and pieces of skin have been cut out and sub- 
 
SENSATION QUALITY 93 
 
 jected to microscopic examination in the hopes of 
 determining these organs, but without success. The 
 permanence of the sensory points has been doubted 
 by many investigators from the first, and it has at 
 last been pretty well established that we have not 
 to do with points, but with large areas, and that the 
 points of maximal sensitivity within these areas 
 vary considerably from day to day. The error of 
 the earlier investigators was in marking the points 
 on the skin, thus prejudicing their succeeding tests 
 on the same areas. 
 
 The latest physiological investigations indicate 
 that there are three sorts of cutaneous and subcu- 
 taneous sensibility from the physiological point of 
 view. These are: (1) Deep sensibility to heavy 
 pressure and to movement of the tissues, as when 
 a member is flexed. (2) Protopathic sensibility, 
 "pain,^' heat, and cold; heat stimulated by temper- 
 atures above 45° C. and cold by temperatures be- 
 low 20° C. (assuming the neutral point to be about 
 37°). (3) Epicritic sensibility, touch and tickle and 
 warmth and coolness; warmth and coolness pro- 
 duced by temperatures lying between the neutral 
 point and 45° and 20° respectively. If certain sen- 
 sory nerves are severed, areas supplied by them 
 lose sensations of the second kind, but the first and 
 
94 A SYSTEM OF PSYCHOLOGY 
 
 third are unaffected. Severance of certain other 
 nerves destroys sensitiveness of the third sort, with- 
 out affecting the first and second. And, finally, 
 severance of certain "motor"' nerves destroys sensi- 
 tiveness of the first sort only. 
 
 These facts indicate that there are two sets of 
 nerve endings giving warmth and cold sensations, 
 but under different conditions — the one set respond- 
 ing to slight stimulations, and capable of only a 
 feeble action, the other set requiring a much greater 
 stimulus, but capable of intense response. These 
 last-mentioned organs may also be excited by me- 
 chanical stimulations, as pressure or cutting. There 
 are perhaps eight types of nerve endings, according 
 to their functions, as follows: tickle, touch, weak 
 warmth, weak cold, heat and "sharp pain,'' cold 
 (strong), deep pressure, and "dull pain" or ache. 
 Or perhaps two sensory processes may be the func- 
 tions of one organ. 
 
 In certain diseases which affect the spinal cord 
 and roots of the nerves, we find interesting dissocia- 
 tions of sensation, differing from those just de- 
 scribed, where nerves are severed at some distance 
 from the spine. In the degeneration of the spinal 
 cord known as syringo-myelia, all sensations of cold, 
 warmth, and "sharp pain" are lost from large areas 
 
SENSATION QUALITY 95 
 
 of the body without affecting touch or pressure. 
 In other diseases touch alone may disappear/ and 
 in other conditions touch and cold are lost, but not 
 warmth and heat. In some instances the sensibility 
 of the hairs alone has been lost. 
 
 II. Kinaesthetic and Coenaesthetic Sensation 
 The muscular and visceral sensations furnish us 
 with another striking illustration of the difficulties 
 which beset psychological analysis. The quali- 
 tative distinctions within these classes are scientifi- 
 cally no less important than in the other sensory 
 groups, yet the distinctions have to go unmade. In 
 the case of the muscular sensations, we attend so 
 predominantly to what the sensations signify — to 
 the ideas they arouse— that we are not able to notice 
 adequately the sensations themselves. Perhaps the 
 ability to attend analytically to these sensations 
 would unfit the patient for the simplest routine of 
 life, so important is it that we attend to what they 
 mean, rather than what they are. 
 
 Under the head of muscular sensation we include 
 all those which result directly from muscular move- 
 
 ^ In the eases reported, however, it is not certain whether 
 deep pressure did not go, too. Tickle undoubtedly was lost, 
 also, but no report is made of that, it being usually assiuned 
 by the clinician to be a form of touch. 
 
96 A SYSTEM OF PSYCHOLOGY 
 
 ment, excepting those already described as dermal 
 and subdermal, although touch, for example, is 
 aroused when the arm is flexed or extended.^ We 
 include, therefore, sensations produced by excita- 
 tion of endings in the muscles,^ in the tendons, and 
 in tissues near the joints. When I raise my arm, 
 the contraction of the muscles excites the platelets 
 which are in contact with its fibres, the change of 
 tension of the tendons probably excites endings 
 therein, and the movements of the head of the hu- 
 merus in the shoulder socket, and of the apposed 
 surfaces in the elbow joint, excite endings in the tis- 
 sues surrounding them; and the sensation-complex 
 resulting from all these excitations — or in the last 
 resort, from their cortical effects — I call the "feel- 
 ing of raising my arm/^ If the muscular contrac- 
 tion occurs, but the arm is held by external force, 
 the details of stimulation in muscle and joint are 
 somewhat different; the muscle does not change its 
 shape so much, and certain nerve terminals are 
 doubtless less stimulated, others more stimulated, 
 than if the movement had occurred, the articular 
 
 ^ For sensory endings in the muscles, see Piersol, fig. 876. 
 
 2 It is possible that the deep pressure already mentioned is 
 really a sensation from nerve endings in the muscles, stirred 
 by the pressure, and ought to be classed as muscular sensa- 
 tion; I am at present inclined to that opinion. 
 
SENSATION QUALITY 97 
 
 surfaces are subjected to pressure, not to friction. 
 This sort of stimulation arouses, through its brain 
 effect, a sensation-complex which we call the " feel- 
 ing of effort," or of "weight." 
 
 Whether different qualities are produced from the 
 joints under different conditions, and whether the 
 relaxation of a muscle arouses a sensation of quality 
 different from that excited by contraction, we can- 
 not say. The differences on which our judgments 
 depend may be all the results of combinations of a 
 single joint-quality and a single muscle-quality, the 
 extensities and intensities varying. 
 
 It is difficult to analyze the organic sensations, 
 not because we do not attend directly to them, but 
 because there is no experimental way of varying 
 them, and they occur normally in such regular com- 
 plexes that the noting of elements is almost im- 
 possible. You must remember that if we saw pur- 
 ple only in the hue called " magenta," and never in 
 the hues nearer the spectral colors, we should proba- 
 bly never guess that it is red jplus blue. So it is with 
 nausea, lassitude, and such organic contents; they 
 may be complexes of elements which occur in dif- 
 ferent combinations, but so regularly that they 
 might as well be elements, so far as our experience 
 goes. We are in much the same position here that 
 
98 A SYSTEM OF PSYCHOLOGY 
 
 we are as regards odors. Whether the elements are 
 many or few, we are unable to tell. 
 
 The organic sensations seem not to be aroused by 
 direct action of external stimulation, and those tis- 
 sues which possess this form of sensibihty alone (as, 
 for instance, the peritoneum covering the intestines, 
 and the intestines themselves), may be pinched, 
 cut, burned, or otherwise maltreated, without the 
 production of any sensation. Even powerful intes- 
 tinal contractions, artificially brought about, pro- 
 duce no effect sensationally. Yet, under certain 
 conditions, which may, for all we know, be chemical 
 stimulations within the tissues, or changes in the 
 channel of flow of the nervous currents originating 
 in these tissues, decided sensational results are pro- 
 duced; witness the juvenile belly-ache.^ 
 
 One sensation-quality which does not quite come 
 under the above description, but which ought per- 
 haps to be included under coensesthesis, is dizziness, 
 or vertigo. This is produced either directly or 
 indirectly by the stimulation of the nerve endings 
 in the semicircular canals. These canals, which 
 lie approximately in three planes, at right angles to 
 
 ^ There is a theory that belly-ache is due to the irritation 
 of the abdominal peritoneum, which is sensitive to pressure, 
 cutting, etc., giving only a ''painful" sensation. 
 
SENSATION QUALITY 99 
 
 each other, and so are sensitive to rotation in any 
 direction, are supplied by a branch of the same 
 nerve which supplies the cochlea, but the sensa- 
 tions are by no means auditory. Pathological irri- 
 tation of the semicircular canals produces sympto- 
 matic dizziness, and if the canals are completely 
 destroyed the patient can no longer be made dizzy. 
 Dizziness is associated with various nervous phe- 
 nomena, notably the rhythmic eye movements known 
 as nystagmus (whirling until one is dizzy will pro- 
 duce these movements), and can be produced in 
 so many ways (eye disease, indigestion, mental 
 shock, are some of the ways) that any conclusion as 
 to the exact function of the semicircular canals is 
 at present impossible. 
 
 The "dark-brown taste ^' to which we have re- 
 ferred earlier is perhaps due to excitation of nerve 
 endings in the mucus membrane by substances 
 produced directly or indirectly as a result of ab- 
 normal chemical changes in the alimentary canal. 
 In the general organic feelings of well-being, de- 
 jection, placidity, etc., as well as in more specific 
 emotional content, it is possible that an important 
 causal factor is stimulation by chemical substances 
 (hormones) secreted by the various ductless glands, 
 and poured by them into the blood. 
 
100 A SYSTEM OF PSYCHOLOGY 
 
 The painful sensation known as ache is apparently 
 the function of various tissues deeper than the skin 
 and mucus membrane. It is a true coenaesthetic 
 sensation, although seemingly allied to intense cold. 
 This suggestion of cold is doubtless a matter of 
 association, cold being a common cause of ache. 
 
CHAPTER V 
 
 THRESHOLDS OF CONSCIOUSNESS 
 I. Stimulus-Thresholds 
 
 In order that a stimulus may produce a sensation 
 it must satisfy certain limiting conditions called 
 stimulus-thresholds. These conditions, which are 
 strictly physical, are matters of (a) wave length or 
 molecular character, (6) intensity or amount of en- 
 ergy per unit of time, and (c) duration of action of 
 the stimulus and extent of area affected by it. All 
 these conditions are capable of being expressed as 
 magnitudes. 
 
 Of the first type we have given one illustration 
 already, in speaking of odors, which must have the 
 molecular weight of HCN at least. Probably sim- 
 ilar determinations may be made for gustable sub- 
 stances. Light-waves must have a length of not 
 greater than circa seventy-five hundred-thousandths 
 of a millimeter (.00075 mm.) and not less than 
 thirty-eight hundred-thousandths (.00038 mm.) in 
 
 order to arouse visual sensation. The longest air 
 
 101 
 
102 A SYSTEM OF PSYCHOLOGY 
 
 vibration which will arouse a sensation of tone 
 is about twelve meters, and the shortest about 
 one-half of a millimeter. These magnitudes are 
 thresholds. 
 
 If we consider ether-vibrations of suflBcient energy 
 falling on a normal retina, commencing with waves 
 too long to be visible and steadily decreasing in 
 length, we can conceive that when a certain wave 
 length is reached a sensation of light will occur; it 
 will "enter the mind" or "enter consciousness'' at 
 that point. This point at which the sensation 
 "steps in'' is accordingly dubbed the threshold. 
 In the cases of sound and light there are two thresh- 
 olds; you can approach the limits of sensibility 
 from either direction; and the same may be true of 
 smell. There may be gases which are odorless be- 
 cause their molecular weights are too great. 
 
 These thresholds are sometimes — and incorrectly 
 — called qualitative. There is no such thing as a 
 qualitative threshold. Clearness and accuracy can 
 be attained by referring to the auditory wave-fre- 
 quency thresholds, the visual wave-length thresh- 
 olds, etc. 
 
 The second sort of thresholds occur in the series 
 of intensities of stimulations, and this sort of thresh- 
 old is always meant by the term when not expressly 
 
THRESHOLDS OF CONSCIOUSNESS 103 
 
 qualified to signify otherwise. These thresholds 
 may be referred to as the acoustical intensity-thresh- 
 old, the optical intensity-threshold, etc. 
 
 The acoustical and optical intensity-thresholds 
 are theoretically measurable as certain amplitudes 
 of waves of a given length (see next chapter), but 
 practically they are measured in a much more 
 primitive way. The acoustical threshold is ex- 
 pressed as the distance through which a given ball 
 must be dropped on a given plate or block, at a 
 given distance from the ear, in order to produce an 
 auditory sensation. The optical threshold is usu- 
 ally determined by finding the proportion in which 
 a given beam of light may be reduced, and yet 
 arouse a visual sensation. As might be expected, 
 such determinations are not very satisfactory. 
 
 The osmical threshold is accurately determined 
 by finding the least amount of a given substance 
 which, infused in a unit quantity of dry air, will 
 produce the appropriate sensation under the best 
 conditions of inhalation. So the geusical threshold 
 is determined by finding the least amount of sub- 
 stance which, dissolved in a unit quantity of dis- 
 tilled water, will arouse taste sensations. 
 
 The haptic threshold is determined by laying 
 weights on the skin or by pressing it with delicate 
 
104 A SYSTEM OF PSYCHOLOGY 
 
 springs of metal or hair, giving known amounts 
 of pressure. The hapto-algetic threshold may be 
 similarly measured by finding the least pressure on 
 a given area producing "pain/' The intensity- 
 threshold for warmth and cold cannot be meas- 
 ured adequately by any simple method. 
 
 The stimulus acting on any organ must act for a 
 certain length of time before a sensation is produced, 
 and, if the intensity is low, a duration may be found 
 which will allow no sensation to be raised into con- 
 sciousness. A light, intense enough to be clearly 
 seen under ordinary conditions, may remain invisible 
 when allowed to fall on the retina for only a few 
 thousandths of a second. Conceivably, this dura- 
 tion-threshold is only an aspect of the fundamen- 
 tal intensity-threshold; for the energy applied in 
 the brief time measured by the duration-threshold 
 is just sufficient to raise the neural process to the 
 point at which a sensation is produced. 
 
 The area- thresh old of stimulation, which is im- 
 portant only in vision, is doubtless also of deriva- 
 tive nature, the energy being distributed over an 
 area wider than that mathematically correspond- 
 ing to the external object or its projection on the 
 organ. 
 
THRESHOLDS OF CONSCIOUSNESS 105 
 
 2. Stimulus Difference Thresholds 
 Two stimuli may be different in intensity, in 
 wave length, in duration, or in some other feature, 
 and yet there may be no difference noticeable in 
 the sensations corresponding to the stimuli. So 
 far, it is an open question whether this failure to 
 observe a difference in the given respect means that 
 the sensations are really the same in that respect, 
 or whether they are necessarily different (assum- 
 ing that the conditions of the organ and environ- 
 ment are equivalent, except in respect to the differ- 
 ence of stimulus under consideration). The fact 
 remains that a certain measurable difference in 
 stimuli is necessary in order that a corresponding 
 difference may be perceived in sensation.^ The 
 magnitude of this required difference is called the 
 difference threshold. The difference threshold is 
 usually expressed as the increment or decrement 
 which must be made to any stimulus before the in- 
 creased or decreased stimulus produces a sensation 
 differing in the corresponding way from the sensa- 
 tion produced by the original or "standard stimu- 
 lus." 
 
 ^ This statement is subject to the consideration of the 
 "Constant Error. '^ See next section. 
 
106 A SYSTEM OF PSYCHOLOGY 
 
 3. Other Thresholds 
 
 There are other thresholds which we have not 
 considered above. Note that we have so far 
 been deaHng with the stimulus-threshold, or the 
 stimulus difference threshold. They are some- 
 times called "sensation-thresholds/' but the other 
 designation is the accurate one. They are always 
 determined by the measurement of stimuli which 
 produce a specified effect before consciousness. 
 There are other thresholds which are not the 
 measurements of stimuli at all. 
 
 We may determine, for example, the least time 
 interval perceptible as such; or the least space in- 
 terval in touch or vision. Or we may determine the 
 difference threshold for time intervals. These mat- 
 ters are not relevant here except to forestall the sup- 
 position that all thresholds are stimulus-thresholds. 
 
 4. The Constant Error 
 
 Suppose I wish to find the stimulus difference 
 threshold for intensity (which for brevity we may 
 call the I. D. T.), for a pressure of twenty-five 
 grams on the centre of the palm of the hand. Ob- 
 viously, the general method of procedure must be to 
 place on the selected spot of the patient's hand 
 
THRESHOLDS OF CONSCIOUSNESS 107 
 
 a weight of twenty-five grams, alternating with 
 weights sHghtly greater and shghtly less, until we find 
 the least weight which is felt as heavier, and the 
 greatest which is felt as lighter, than the twenty-five- 
 gram ("Standard") weight. The elaborate tech- 
 nic and many precautions necessary to make our 
 results significant, we need not describe here, but 
 one feature of the experiment is of present impor- 
 tance: If the "Standard'^ weight is given first in 
 each case, and the second weight ("Variable") is 
 varied appreciably, the patient (who, of course, is 
 not allowed to see the hand and weights, and is not 
 informed as to their actual weight values), will in 
 very many cases declare the "Variable" heavier 
 or lighter than the "Standard", when the two are 
 exactly equal. You may find at the end of your 
 experiment, for example, that the weight which is 
 on the average just perceptibly heavier than the 
 "Standard," when the "Standard" is given first, is 
 actually lighter than the "Standard"! But this 
 disconcerting result is not at all erroneous or 
 troublesome. If you make an equal number of 
 experiments with the "Variable" first and the 
 "Standard" last, you may find the results the con- 
 verse of the first set — the just perceptibly lighter 
 weight being now heavier than the "Standard." 
 
108 A SYSTEM OF PSYCHOLOGY 
 
 In short, your results include two factors; the 
 I. D. T., and the constant error (C. E.) due to the 
 order of the weights. The second of two weights 
 is not judged under the same conditions as is the 
 first, and vice versa. You must always make ex- 
 periments in both time orders (S-V and V-S), and 
 by comparing the results in the two cases determine 
 the C. E. of time order, before you can determine 
 the approximate D. T. 
 
 Constant errors, due to all sorts of factors, con- 
 tribute to the complexity of the problems of experi- 
 mental psychology, and in many cases the determi- 
 nation of the magnitude of the C. E. under definite 
 conditions becomes a method of solving important 
 problems. 
 
CHAPTER VI 
 
 SENSATION-INTENSITY 
 I. Intensity of Sensation and Intensity of Stimulus 
 
 As we have already implied, the intensity of sen- 
 sation depends in general on the intensity of the 
 process in the end-organ and brain, which in turn 
 depends in part on the intensity of the physical 
 stimulus. There are, therefore, two relations to be 
 considered: (1) the relation between the stimulus 
 and the nervous process, and (2) the relation be- 
 tween the nervous process and the sensation. Con- 
 cerning each of these relations we have practically 
 nothing but the bare fact that, ceteris paribus, an 
 increase in the intensity of one is connected with 
 an increase in the intensity of the others. 
 
 The condition of the sense-organ has an important 
 influence on the intensity of the sensation result- 
 ing from a given stimulation : fatigue and adaptation 
 can modify the result immensely. Thus, the light 
 sensation aroused by light striking the dark-adapted 
 eye may be very much brighter than the sensation 
 
 aroused by a light many times more intense acting 
 
 109 
 
110 A SYSTEM OF PSYCHOLOGY 
 
 on the light-adapted eye. These facts do not offer 
 any serious logical obstacle to the formulation of 
 statements of intensity relation, as all such are sim- 
 ply required to specify that the relation holds only 
 for a uniform condition of the sense-organ and 
 nervous connections; but they introduce serious 
 practical diflBculties, because it is not always possi- 
 ble to ascertain whether the condition of an organ 
 is uniform during any given period of experimenta- 
 tion. 
 
 The diflficulty of the discovery of definite inten- 
 sity relationships of sensation and stimulus is in- 
 creased by the difficulty of estimation. Direct meas- 
 urement of sensation-intensities is impossible. We 
 can only compare one sensation with another, and 
 determine which of the two is more intense. And 
 this determination is strictly relative. The apparent 
 intensity of a sensation is affected by other sensa- 
 tions, aside from any change in the actual intensity 
 of the sensation. For instance: a candle burning 
 near a coal-oil lamp seems dimmer than the same 
 candle burning beside the flame of a minute gas- 
 jet; yet, if the experiment is performed in moder- 
 ate daylight, the candle flame is practically as 
 bright sensationally in the one case as in the other. 
 When the time factor enters, and sensations pres- 
 
SENSATION-INTENSITY 111 
 
 ent are compared with past sensations, the relativity 
 of the judgment of comparison becomes greater. 
 But even when the time factor is not present, 
 the comparison of sensations of any sense is rel- 
 ative. 
 
 Taking into account the relativity of sensations 
 and the relativity of the estimation of sensations, 
 we find diflBculties enough to account for the fact 
 that no laws of the quantitative relation of stimulus- 
 intensity to sensation-intensity are discoverable at 
 present. The nearest approach to a law of this kind 
 is "Weber's Law," which deals with the intensity 
 difference threshold only. 
 
 2. Weber's Law 
 
 If we express the intensity D. T. as a ratio of 
 the just perceptible increment (or decrement) to 
 the Standard, we may state Weber's Law in the 
 following terms: The I. D. T. for different values 
 of a standard stimulus varying in intensity only is 
 practically constant if the general condition of con- 
 sciousness remains the same. This law holds, how- 
 ever, only for mean ranges of intensity; for feeble 
 or very high intensities it is invalid. 
 
 Weber's Law may be expressed less technically, 
 but yet accurately, as follows: The ratio of the 
 
112 A SYSTEM OF PSYCHOLOGY 
 
 intensity of a standard stimulus to the just percepti- 
 ble increment in intensity is the same as the ratio 
 of the intensity of any other standard to its just 
 perceptible increment (or decrement), provided 
 the sensations aroused by the two standards differ 
 only in intensity, and provided that the general 
 mental and physical condition of the patient is the 
 same in the tests with the different standards. There 
 will be in any case a minimum standard and a 
 maximum standard, below which and above which, 
 respectively, the equality will not hold. 
 
 As a concrete example of the uniformity described 
 by Weber^s Law, we may give the following. If the 
 pressure of fifty grammes on the finger needs to be 
 increased to fifty-one grammes in order that the in- 
 crease may be noted, the pressure of one hundred 
 grammes will need to be increased to one hunderd 
 and two. In other words, the I. D. T. at fifty 
 grammes (^) is the same as the I. D. T. at one 
 hundred grammes (y^)- Above perhaps four hun- 
 dred grammes, and below perhaps ten grammes, the 
 ratio will be somewhat different. 
 
 The provisions to which we have given place in 
 the formulations are exceedingly important. Among 
 other cases in which these provisions preclude our 
 expecting the I. D. T/s to be equal, the following 
 
SENSATION-INTENSITY 113 
 
 may be noted: (1) Different senses, or different 
 qualities; thus, we would not expect to find the 
 I. D. T. for sugar the same as that for blue light, 
 or even for salt. (2) Different individuals. (3) 
 Different portions of the sense-organ, as the centre 
 and periphery of the retina. (4) Different exten- 
 sities or durations of sensation. (5) Different con- 
 ditions of the patient, as rested and fatigued. In 
 addition, we do not find a constant D. T. for any 
 other character than intensity. Weber's Law has 
 no bearing on the D. T. for color change (wave 
 length), or pitch, or duration. It applies to inten- 
 sity only. 
 
 Weber's Law was given its name in honor of 
 E. H. Weber, who first discovered the facts which it 
 describes. The first formulation, and the appli- 
 cation of the name, were the work of G. T. Fech- 
 ner, who attempted to give the law an application 
 to stimulus differences greater than those just per- 
 ceptible, and to turn it into a statement of the re- 
 lation of stimulus-intensity to sensation-intensity. 
 Fechner's attempt, based on the assumption that all 
 just-perceptible differences in sensation are equal, 
 resulted in "Fechner's Law," and "Fechner's 
 Formula," which expressed the relation as a logarith- 
 mic equation. The discussions, controversies, and 
 
114 A SYSTEM OF PSYCHOLOGY 
 
 investigations consequent on this formulation con- 
 stitute the subject sometimes called psycho-physics. 
 Fortunately for the student, the whole matter is 
 chiefly of historical importance, and may be safely 
 ignored in an elementary course/ 
 
 3. The Comparison of Intensity Differences 
 
 The determination of the just perceptible differ- 
 ence involves an equating of intensities. In order 
 to find what intensities seem equal to a given inten- 
 sity, we must find the greatest which seems less and 
 the least which seems greater; conversely, in de- 
 termining these thresholds, we have substantially 
 determined the intensity equivalents. In addition 
 to finding equal-seeming intensities of sensation we 
 may also compare differences of intensity with re- 
 gard to their equality or non-equality; but we find 
 that the results of these judgments are less uniform 
 than those of mere intensity. 
 
 If we find two sensations, Si and S2, which ap- 
 
 ^ The analytically inclined student may be disturbed by 
 the careless way in which we speak of the discriminating of 
 differences of stimuli, instead of the discriminating of differ- 
 ences of sensation corresponding to certain differences of stim- 
 uli. We trust, however, that the discussion gains in simplic- 
 ity without losing in clearness by that looseness. 
 
 For an adequate discussion of Fechner's addition to Weber, 
 see James, Principles of Psychology, vol. I, chap. XIII, pp. 
 533-549. 
 
SENSATION-INTENSITY 115 
 
 pear exactly as different in intensity as two other 
 sensations, S3 and S4, we might expect to find on the 
 analogy of Weber's Law, that the stimuli of the 
 first pair have the same intensity-ratio as the stimuli 
 of the second pair. Letting the intensity of the 
 stimulus be represented by R, the relation in ques- 
 tion may be expressed, Ri/R2 = R3/R4. This rela- 
 tion, which is demanded by Fechner's Formula, 
 is actually found to hold in many cases. In other 
 cases, however, the relation has been found to be 
 more nearly that of equality of stimulus differences; 
 Ri— R2 = Rs — R4, and this divergence has given rise 
 to some acrimonious controversy over the " correct- 
 ness'' of the one result or the other. As a matter 
 of fact, both are correct. Some individuals will 
 rather uniformly select "equahties" of the first 
 type, and other individuals will select equalities of 
 the second type. Certain individuals will select 
 neither type of equality, and still others will select 
 both} 
 
 ^ In extensive experiments on nearly sixty persons, using 
 the same apparatus and same conditions throughout, I have 
 found that in selecting a light-brightness or weight-intensity 
 which seemed midway between two standard light or pressure 
 intensities, the persons fell into four classes: (1) Those who 
 selected the geometrical mean; (2) those who selected the 
 arithmetical mean; (3) those who selected a mean which was 
 the arithmetical mean of the geometrical and arithmetical 
 mean; (4) those who selected approximately the harmonic 
 
116 A SYSTEM OF PSYCHOLOGY 
 
 4. The Relativity of Sensation 
 
 The relativity of sensation-intensity and inten- 
 sity-differences; their variability, that is, according 
 to the various conditions mentioned in the preced- 
 ing sections, may account for the apparent ^'^ rela- 
 tivity" of sensation-quality, w^hich is usually in- 
 cluded by specification or implication in references 
 to the " relativity of sensation/' It is often implied 
 that the quality of a sensation is not determined by 
 a definite stimulus acting on a corresponding ner- 
 vous mechanism, but by this action in conjunction 
 with all the other nervous and mental activities. 
 Color contrast, and all the other conditions in which 
 now this sensation, now that, are gotten from the 
 same stimulus under different conditions, are cited 
 in support of this view. These phenomena may 
 not be due to qualitative variability at all, but sim- 
 ply to the variability of intensity. 
 
 A qualitative change in a sense-content may be 
 one of three things. (1) It may be a change in the 
 intensity or intensities of one or more of the quali- 
 
 mean. Some of the persons were too irregular to be fairly 
 classified at all, a few alternated between two types, and one 
 person insisted on selecting two means, approximately the 
 arithmetical and geometrical, which he insisted were both 
 good, although not ''of the same sort." 
 
SENSATION-INTENSITY 117 
 
 tative elements present in the content. (2) It may 
 be the addition of a qualitative element, or of 
 qualitative elements not previously present. (3) It 
 may be a simulation, due to a direction of the atten- 
 tion more strongly or less strongly to certain ele- 
 ments. 
 
 A sensation of pure red (if such is obtainable) 
 may become more intense, or less intense, and may 
 completely disappear; but, so long as it remains, it 
 can be nothing but red. The same stimulus which 
 now arouses pure red may, in a different condition 
 of the eye, arouse some blue also; in which case the 
 result is purplish. So daylight, which ''normally^' 
 excites the three colors in such proportions of in- 
 tensity that "white'^ results, may, if the eye is 
 adapted to purple light, excite the green process 
 with unusual intensity; hence, the green after-image. 
 Distilled water does not ordinarily excite the taste- 
 buds, and hence there is no gustatory sensation; 
 but by the previous action of some drug the nerve 
 endings may be made sensitive to the effect of the 
 water; this is, in effect, the lowering of the stimulus- 
 threshold. 
 
118 A SYSTEM OF PSYCHOLOGY 
 
 5. Beats 
 
 An important phenomenon of intensity in the 
 auditory realm is that of beats. Beats are periodic 
 fluctuations in the intensity of a sound, commonly 
 arising when the stimulus (air-waves) is composed 
 of vibrations from two separate sources, as two 
 tuning-forks, or pipes, or strings, giving notes of 
 proper pitches. Two sources of sound will give 
 rise to beats if (1) the note of one is less than (circa) 
 thirty vibrations per second faster than the other, 
 or (2) when twice the rate of the lower is less than 
 thirty vibrations faster or slower than the other. 
 These beats are called beats of the first and second 
 orders respectively. Beats of the third and higher 
 orders exist theoretically, but are so weak as to be 
 practically negligible. For the physical theory of 
 the interference of the sound-waves, which produces 
 the alternate maxima and minima corresponding 
 to the beats in sensation, the student may refer to 
 any good treatise on sound, or on general physics. 
 
 A single source of sound, as, e. g., sl bell, may pro- 
 duce beats through the interference of the partial 
 tones contained in its note. It is this which gives the 
 tremulous character to the sound of a bell. Alter- 
 nate reinforcement and diminution of the intensity 
 
SENSATION-INTENSITY 119 
 
 of a single note may be produced also by various 
 extrinsic means. Tune a bottle to the note of a 
 tuning-fork by pouring in water to the right height, 
 and then rotate the fork, holding it horizontally over 
 the mouth of the bottle: the beats thus produced 
 are of the same character as those produced by two 
 forks sounding together. The vibrato or tremolo 
 of the human voice, which is an effective embellish- 
 ment when used sparingly, and which mediocre 
 singers employ without reason or mercy, is in some 
 cases purely a matter of intensity-variation, i. e,, 
 beats; in other cases (in most cases, in fact) it is 
 partly a matter of pitch changes. 
 
CHAPTER VII 
 
 PROTENSITY AND EXTENSITY OF SENSATION 
 I. The Duration-Character 
 
 The duration or protensity of a sensation is to be 
 discriminated from the duration of the experience, 
 and from the duration of the stimukis. A stimulus 
 acting one second may produce a sensation lasting 
 less than a second or more than a second. The 
 sensation may not be experienced during a certain 
 period of its existence; perhaps it may not be ex- 
 perienced at any time; at least there are sensations 
 which are unnoticed during a part or the whole of 
 their existences. We cannot say with certainty that 
 any sensation is experienced from beginning to end; 
 perhaps all sensations have unexperienced phases. 
 Even if we should admit, as certain metaphysicians 
 would have us do, that the duration of the sensation 
 and the duration of the experience of the sensation 
 are equal and coterminous, we should still be obliged 
 to hold that the duration of the one is logically dis- 
 tinct from the duration of the other, for the duration 
 
 which is characteristic of the sensation is actually 
 
 120 
 
PROTENSITY AND EXTENSITY 121 
 
 experienced along with the other characters (quality, 
 intensity, etc.). In other words, the duration ex- 
 perienced is not the same thing as the experience of 
 the duration. 
 
 The protensity or duration of the sensation as di- 
 rectly experienced is distinguished from the duration 
 as measured by its relation to series of other events, 
 whether these events are other sensations directly 
 experienced (as in the immediate estimate of time) 
 or whether they are members of an ideal series 
 based on mathematical subdivisions of the parallel 
 of latitude (minutes and seconds).^ 
 
 It is the duration of sensation as an experienced 
 fact to which we refer in speaking of the protensity 
 or duration-character. A sensation without it could 
 never be brought into the time relation, and time, as 
 we experience it, could not exist apart from sensa- 
 tions. Time, however, involves more than sensa- 
 tion-duration, as we will see later. 
 
 The direct comparison of two sensation-durations 
 is much more diflBcult than the comparison of in- 
 tensities. In the first place, it is impossible to ex- 
 
 ^ This mathematical relation of sensation-duration to a 
 standard time series is often loosely designated the " duration 
 of sensation " as distinguished from the '' experience of the 
 duration," the last name being applied uncritically to the 
 duration-character of the sensation, the estimated duration, 
 and the experience of these. 
 
122 A SYSTEM OF PSYCHOLOGY 
 
 elude a multitude of other sensations (bodily, etc.) 
 which insist on taking a part in the comparison. 
 In the second place, since in most cases the dura- 
 tions compared must be in succession, the memory 
 factor becomes especially disturbing. For these 
 reasons, very little has actually been accomplished 
 in the investigation of the difference-sensibility for 
 protensity, although there has been a great deal of 
 experimentation in the general field of time-content. 
 
 2. Extensity 
 
 Extensity is related to space as protensity is to 
 time. In each case the sensation-character is so 
 intimately built up into the complex that it is diffi- 
 cult to analyze it out; but the analysis is the less 
 difficult in the case of extensity. 
 
 Extensity can best be demonstrated in the dermal 
 sense. Provide yourself with a small cork stopper 
 and a small wooden rod with a blunt, very slightly 
 rounded point. Touch yourwrist or lower arm alter- 
 nately with the rod and with the cork, avoiding hairs 
 and veins, and pressing just hard enough to arouse 
 touch sensations. Notice that the touches have 
 different '* bigness'^ although neither has any space- 
 form; that is, you cannot discriminate any parts in 
 either; you cannot discriminate edge from middle. 
 
PROTENSITY AND EXTENSITY 123 
 
 or one side from the other. The difference which 
 you observe is one of extensity. In a corresponding 
 way, extensity-differences may be demonstrated in 
 the visual field. 
 
 Extensity-differences depend physiologically on 
 differences in the number of nerve endings stimu- 
 lated. In general, the more nerve endings stimu- 
 lated, the more extensive the sensation, but we can- 
 not expect to find any definite relation of number 
 to extensity which would hold for different parts of 
 the organism, or even for different parts of a sense 
 organ. Extensity-differences occur wherever there 
 are nerve endings capable of stimulation in different 
 numbers, as in the senses of vision, touch, warmth, 
 cold, and bodily feeling.^ 
 
 In the case of auditory sensations, the extensity, 
 if it exists, is probably that which we commonly 
 
 ^ The difference in volume between different aches, for 
 example, is often noticed. In smelling, it is possible that 
 practically the whole group of nerve endings which are ca- 
 pable of responding to a given odor are stimulated every time 
 the odor is aroused, as we find no pronounced differences of 
 extensity with any one odor. Whether different odors have 
 different extensities we cannot say conclusively. The sen- 
 sations of smell, nevertheless, have extensity, even though 
 differences therein are obscure; it is the apparent (or real) 
 sameness or the practical unimportance of differences, which 
 makes us overlook the character in olfactory experience. Yet 
 we ought not to say even that it is practically unimportant, 
 until we are certain that it plays no part in the puzzHng com- 
 position of odors. 
 
124 A SYSTEM OF PSYCHOLOGY 
 
 call "pitch. The nerve endings (the hair-cells) in the 
 cochlea of the ear form a linear series (or multiple 
 linear series) running the length of the basilar mem- 
 brane, and it is probable that high notes (rapid vi- 
 brations) stimulate only the cells situated at the 
 end nearer the middle ear; lower notes (slower vi- 
 brations) stimulating a larger number. It is well 
 known that the destruction of the cochlear nerve 
 endings nearest the middle ear (at the basal extrem- 
 ity of the basilar membrane) destroys the sensitiv- 
 ity of the ear for high tones, but not for low ones, 
 and this agrees well with the extensity theory, but 
 with no other except that of Helmholtz. 
 
 The introspective fact that the difference between 
 low and high tones seems like the difference of ex- 
 tensity of other sensations; the fact that the sound- 
 ing of a low tone obscures a feeble high tone, while 
 the sounding of a high tone does not obscure a 
 feeble low tone; the fact that the highest audible 
 tone, no matter what its actual pitch, always seems 
 '* approximating zero," that is, having no conceiv- 
 able terms beyond it in the pitch series; these and 
 other facts point to the correctness of the pitch-ex- 
 tensity theory. 
 
 Pitch is no more noticed habitually as a mere 
 sensation-character than are extensities of other 
 
PROTENSITY AND EXTENSITY 125 
 
 sensations. We do not weave it into a space system, 
 probably because of the lack of muscular adjust- 
 ments for that function, but we do, nevertheless, or- 
 ganize the different extensities in the usual mathe- 
 matical way. One result of the organization is the 
 musical scale, and we normally perceive tones in 
 the scale relation, although usually not with mathe- 
 matical exactness. Exactness is attainable for 
 theoretical purposes, just as exact space measure- 
 ments are possible in spite of the fact that our 
 ordinary estimations of space "by eye^^ are mere 
 approximations to accuracy. 
 
 3. Overtones and the Musical Scale 
 
 The method in which the diatonic scale which we 
 use (in theory) at present, and the modifications of 
 it employed in musical practice, were developed, is 
 an interesting and important chapter in the psychol- 
 ogy of auditory sensation, but a chapter which can 
 only be sketched at present. The scale has de- 
 veloped through the need of conforming to the 
 natural series of overtones or partial tones (see be- 
 low), the advantage of avoiding beats, and the 
 simplicity of wood-wind instruments with regularly 
 spaced finger-holes (primitive flutes), these instru- 
 ments giving scales which are " near '^-dia tonic. 
 
126 A SYSTEM OF PSYCHOLOGY 
 
 Overtones, or partials, are tones that sound along 
 with the proper or fundamental tone of a source of 
 sound; or, rather, they are components in the total 
 note, which are higher in pitch than the principal 
 component or fundamental. Partials of various 
 number are produced by all the common sources of 
 sound, and may be easily demonstrated with an in- 
 strument of the "sonometer'' type; a long gut or 
 piano wire stretched on a sounding-board or box. 
 Strike the string with a piano hammer (a small rod 
 wrapped with cloth will do) at a point one-quarter 
 the distance from one end to the other, and then 
 touch it lightly in the middle with a feather or small 
 wad of cotton; the fundamental note of the string 
 will stop, but a note an octave higher will continue 
 sounding. This octave tone is called the first over- 
 tone, or the second partial (the fundamental being 
 the first partial). Strike the string at one-sixth and 
 touch at one-third, and you will hear the third 
 partial. Strike at one-eighth and touch at one- 
 quarter, and you hear the fourth partial. If you 
 touch where you have struck, the partial correspond- 
 ing to the point of touching will not be produced, or 
 will be very faint; this shows that it is the striking 
 and not the subsequent touching that produces the 
 partial; which means that the upper partial is pro- 
 
PROTENSITY AND EXTENSITY 127 
 
 duced along with the fundamental. With a Httle 
 practice you can in fact soon acquire the abihty to 
 pick out the partials without touching or stopping 
 the string. 
 
 In instruments of the horn or trumpet type, with 
 proper blowing and without manipulation of the 
 valves or slides, the partials up to the eighth or 
 ninth may be made to sound without the partials 
 below the particular one sounded in each case. 
 This gives a sort of scale whose notes are far apart 
 at the bottom and closer at the top, and in this scale 
 we can play the melodies known as "bugle calls.'' 
 Since these notes (with a modification of the sev- 
 enth) are included in the diatonic scale (in the brass 
 instruments of the modem orchestra we simply add 
 the intermediate notes by manipulation of the valves 
 or slides) we may reasonably suspect that such 
 wind instruments have been important in fixing the 
 notes of the modern scale. 
 
 In another way the partials have helped to fix 
 the intervals of the scale, especially the octave, the 
 interval between the fundamental and the second 
 partial, which is relatively strong in the human 
 voice. In a room or cave some of the notes pre- 
 viously sung are still vibrating while another is 
 being sung (or played) so that the present note must 
 
128 A SYSTEM OF PSYCHOLOGY 
 
 "harmonize" with the overtones of the previous 
 note. 
 
 The musical interval between two notes is meas- 
 ured by the ratios of the vibration-frequencies of the 
 two notes to each other; thus, the note of 256 vibra- 
 tions per second and the note of 320 vibrations per 
 second are separated by the same interval as the 
 notes of 320 and 400, the interval, namely, of 4:5. 
 The intervals separating the successive notes of 
 the diatonic scale (c, d, e, f, g, a, b, c; or ut, re, 
 mi, fa, sol, la, si, ut), may all be expressed by small 
 fractions, and are f , ^, \f, f , ^, f , f|. The rela- 
 tive rates of vibration of the notes separated by 
 these intervals may, therefore, be represented by the 
 numbers 8, 9, 10, lOf , 12, 13J, 15, 16. The rates 
 of vibration of the harmonic partials (the partials 
 of the voice and of musical instruments are prac- 
 tically harmonic) are 1, 2, 3, 4, 5, 6, 7, 8, and so on; 
 the second vibrating twice as fast as the first, the 
 third three times, the fourth four times, and so on.^ 
 It is evident that the diatonic scale is the series of 
 harmonic partials from the eighth to the sixteenth, 
 
 ^ The harmonic partials are those whose vibration-rates are 
 integral multiples of the rate of the fundamental. A partial 
 whose rate is 2<j times that of the fundamental would be 
 classed as non-harmonic. Tuning-forks, bells, and metal 
 plates produce non-harmonic partials. 
 
PROTENSITY AND EXTENSITY 129 
 
 with lOf substituted for 11, and 13J for 13 
 and 14. 
 
 The partials up to the ninth are, as said before, 
 easily produced on wind instruments (and of course 
 on stringed instruments, in isolation, by stopping the 
 strings as described), so we are not surprised to find 
 that in the earliest scales discoverable, in India, 
 China, and the British Isles, these intervals are in- 
 cluded. The notes employed in these scales are, 
 as represented in our scale, c, d, e, g, and a|:[ , or 8, 
 9, 10, 12, 13J. Now the most obvious thing about 
 tl^e overtone series is the octave relation, 1 : 2, 2 : 4, 
 4 : 8, etc., so that the intervals 8 : 10 : 12 : 14 : 16 
 are equivalent to the intervals 4:5:6:7:8; and 
 hence all the intervals of the primitive scale are 
 really given by the overtone series up to nine, ex- 
 cept that the seventh partial is replaced by a slightly 
 lower note. 
 
 The modification of the seventh partial is the 
 first step in the process of simplification which has 
 given us the modern scale; for as the series 8:9: 
 10 : 12 : 14 : 16 gives no two intervals alike, the 
 slight flatting of 14 to 13| replacing 12 : 14 = 6 : 7 
 by 12 : 13^ = 8 : 9, or, still better, flatting to 13 J 
 and so replacing 12 : 14 : 16 by 12 : 13J : 16 = 
 9 : 10 : 12, thus duplicating intervals already in the 
 
130 A SYSTEM OF PSYCHOLOGY 
 
 scale, simplifies matters much. In the same way, 
 when it was desired to insert additional notes in the 
 larger gaps, the notes chosen were not 11 and 13, 
 but such notes as would introduce the fewest new 
 intervals; and these would be the notes 8 : 9 above 
 13J and 8 : 9 below 12, i. e., lOf and 15, which in- 
 troduce only one new interval, 10 : 10§ = 15 : 16/ 
 The scale as derived contains, therefore, only three 
 different successive intervals; 8:9, 9 : 10, and 
 15 : 16; the major tone, minor tone, and semitone. 
 Having derived these three intervals, the ingenuity 
 of musicians led to the combination of the inter- 
 vals in other orders to fill out the octave, but the 
 one which came nearest to the overtone series is the 
 one which has survived in use. 
 
 A still further development has displaced the 
 diatonic scale, which is practically not used at all 
 now. If a note is inserted between 8 and 9, 15 : 16 
 below 9; and another 15 : 16 above 8, the two 
 notes (8 xV ^nd 8 xe) are separated by an interval of 
 2025 : 2048. The pairs of notes similarly placed 
 between 10| and 12, and 13|^ and 15 are separated 
 by the same interval, and the pairs between 9 and 
 
 ^ The interpolations of course made by sound, not by the 
 abstract ratio; but the proper sound is obtained only if the 
 physical conditions which are expressed by the mathematical 
 ratio are observed. 
 
PROTENSITY AND EXTENSITY 131 
 
 10, and 12 and 13J by a slightly larger interval. In 
 the scale derived in this way — the chromatic scale — 
 ab is slightly lower than g^, and so on. So much 
 for the amplification of the scale; now for the sim- 
 plification. The chromatic scale is absolutely im- 
 practicable except for a few gifted musicians. If 
 a single note standing between the proximate sharp 
 and flat were substituted for the two, the resulting 
 scale of twelve notes would be simpler, but too irreg- 
 ular. The obvious way to reduce the irregularities 
 is to divide the octave into twelve equal parts, doing 
 away at one stroke with the distinction between 
 ail and bb, etc., and with the two sorts of whole 
 tones (8 : 9 and 9 : 10) and the two sorts of major 
 fifths. Thus we have a scale called the equally 
 tempered scale, which is a little less satisfactory than 
 the chromatic scale in some respects, but immensely 
 superior in other ways. The equally tempered 
 scale has proved so superior to all other tempered 
 scales (other scales constructed to simplify the 
 chromatic scale) that it is universally adopted, and 
 all modern keyed instruments are tuned in it — or, 
 we might say,' tuned to it, since tuners do not always 
 succeed. 
 
 The Chinese and the Hindus achieved a twelve- 
 fold division of the octave, as did probably the 
 
132 A SYSTEM OF PSYCHOLOGY 
 
 Greeks also. Any people influenced by the har- 
 monic partials and alive to practical musical needs 
 was certain to hit upon some sort of tempered scale. 
 The Chinese and Hindus went still farther, and 
 worked out subdivisions smaller than the twelfth of 
 the octave, but seem to have made little practical 
 use of these minutely built scales. Savage peoples, 
 who had not harmonic instruments (horns, etc.) and 
 whose music was produced out-of-doors, seem to 
 have developed scales not built in the octave at all. 
 This statement applies to some North African 
 tribes, at least, and to ancient Egyptians of low 
 caste. Information on these matters is for the most 
 part seriously defective, even in regard to existent 
 tribes, and much observation has been rendered 
 worthless by the assumption of the observer that 
 the savages are attempting to use intervals repre- 
 sented in the diatonic scale, and that their devia- 
 tions from these ideal intervals are due to their 
 clumsy vocalization and inaccurate "ear.'^ 
 
 4. Timbre 
 
 The character of the tones of different instru- 
 ments, or, as we say, their timbre, is altogether de- 
 pendent on the presence of overtones or upper par- 
 tials. The particular partials present, and their 
 
PROTENSITY AND EXTENSITY 
 
 133 
 
 relative intensities, determine the voice of the in- 
 strument. 
 
 The partials depend on the fact that the string, 
 or column of air, or other vibrating body, is vibrat- 
 
 FiG. 9. 
 
 Fig. 10. 
 
 Fig. 11. 
 
 Figures 9, 10, and 11 are intended to represent schematically the 
 relations of fundamental and overtones in notes of the organ-pipe, 
 violin, and clarinet, respectively. The pitch is represented by the 
 length from left to right, and the intensity by the height from top 
 tol)Ottom. The relative intensities of the partials in a given figure 
 are somewhere near those actually existing in the characteristic notes 
 of the instrument. In the representation of pitch the length of the 
 partials is arbitrarily made inversely proportional to the vibration rate. 
 Notice that in the case of the clarinet (fig. 11) the second partial is 
 missing, while the third partial is relatively strong. 
 
 ing not only as a whole, but in segments. The in- 
 tensities of these segmental vibrations depend on 
 the form and material of the sonorous body and the 
 way it is excited or set in motion. The voice of a 
 violin, for example, depends in large measure on 
 the condition of the wood, glue, and varnish of 
 
134 A SYSTEM OF PSYCHOLOGY 
 
 which it is made, and the way in which it is bowed. 
 Pick the strings, and the note is not only short in 
 duration, but has a characteristic timbre because 
 the relative strengths of the partials are not the 
 same as when the string is bowed. The difference 
 between the tones of a cylindrical flute and a clari- 
 net is partly due to the "bell'' on the end of the 
 clarinet, but more to the excitation of the flute by 
 blowing across a hole and of the clarinet by blow- 
 ing through a reed. The note of the trumpet dif- 
 fers from that of the cornet because of the differ- 
 ent taper of its bore. 
 
 5. Extensity and Intensity 
 
 Extensities are comparable in the way in which 
 we compare intensities, and we find difficulty in 
 abstracting the extensity-differences from the more 
 complex space-differences just as we find in the 
 case of duration and time. The physical measures 
 of just perceptible differences are found to increase 
 with the extensities compared, but apparently 
 not in such a simple way as is formulated for in- 
 tensities in Weber's Law. In pitch, in general, 
 when we can succeed in neglecting the metrical 
 factor of scale relationships, differences seem equal 
 when the corresponding differences in vibration 
 
PROTENSITY AND EXTENSITY 135 
 
 rate are equal. This may mean equal diflferences 
 in number of nerve endings stimulated. 
 
 Intensity is influenced by extensity, and vice 
 versa. It is well known that a small spot of light 
 falling upon the retina is sensationally not so bright 
 as a larger spot of the same physical intensity per 
 unit of area. A weight of one gram resting on one 
 square centimeter of skin feels not so heavy as a 
 weight of ten grams resting on ten square centi- 
 meters. A gustable solution applied to half of the 
 tongue is productive of a stronger flavor than the 
 same solution applied to a smaller area. These 
 effects are in part due to the relatively greater ex- 
 tent of margin of a small area, and the consequent 
 greater reduction of stimulus energy through irradi- 
 ation to surrounding areas, but there may be other 
 causes at work. In the case of auditory sensation, 
 the conditions are such as to appear at first the 
 reverse of those described above; a high note of 
 given energy sounding more intense than a low note 
 of same energy. This is doubtless because a high 
 note affects a fewer number of nerve endings, and 
 hence the actual stimulating energy is greater per 
 unit of nerve ending than in the case of the lower 
 note. 
 
 Intensity frequently affects extensity through the 
 
136 A SYSTEM OF PSYCHOLOGY 
 
 spreading or irradiation just mentioned. The ex- 
 citation from a strong stimulus spreads out over a 
 larger area in the sense-organ than in the case of a 
 weak excitation. This is readily demonstrated in 
 vision by noting the apparent increase in size of an 
 electric light filament as it begins to glow. 
 
 The reader should note that our statement that 
 intensity influences extensity, and vice versa, is meta- 
 phorical, and that the exact statement in terms of 
 the two characters and the corresponding features 
 of the stimulus is that the stimulation-conditions 
 which determine the extensity and the intensity of 
 sensation are in certain cases, at least, mutually de- 
 pendent. 
 
CHAPTER VIII 
 
 LOCAL SIGNIFICANCE 
 I. Localization and Local Sign 
 
 Sensations of touch and temperature on any 
 part of the body are "localized'^ more or less cor- 
 rectly; that is, are felt as coming from the locality 
 of actual origin. This discrimination must be 
 based on diflferences in the sensations from the 
 different regions, which sensations we have come to 
 be able to refer to the proper places. Suppose, for 
 instance, your eyes are closed, and some one noise- 
 lessly touches you on the hand, using a small rod 
 of cork to obviate temperature sensations. You 
 can decide at once that it was on the right hand and 
 not on the left; which is sufficient proof that the 
 sensation from the one hand is different from the 
 sensation from the corresponding point of the other 
 hand. The important question is: What are the 
 differences which serve as the basis of this local 
 discrimination ? Differences in intensity, exten- 
 ^ sity, and duration can be ruled out, for variations in 
 
 these regards do not influence localization except 
 
 137 
 
138 A SYSTEM OF PSYCHOLOGY 
 
 in extreme cases. Differences in quality are also 
 excluded, for the tactual sensation has probably 
 the same quality everywhere on the skin, and tem- 
 perature sensations, which may certainly be ob- 
 tained in different regions with identical quality, 
 are also localized. 
 
 The fact that localization does not depend on 
 quality is more apparent in the case of the eye. 
 Stimulations of different points of the retina (if not 
 too close together) are always discriminated as dif- 
 ferent, and by habitual association referred to the 
 relative angular positions from which the stimulat- 
 ing rays of light must come. The discrimination 
 of positions in the visual field depends, in short, on 
 the discrimination of positions on the retina. And 
 though the hue of a color roused by a given light 
 stimulus varies according to the part of the retina 
 stimulated, there are many different points in the 
 retina giving the same qualitative mixture, which 
 are, nevertheless, discriminated. The hues, more- 
 over, may be varied through the whole range of the 
 spectrum without affecting the locality discrimina- 
 tion; the discrimination, therefore, cannot depend 
 on quality. 
 
 The character of sensation which furnishes the » 
 real basis for localization is thus demonstrable only 
 
LOCAL SIGNIFICANCE 139 
 
 by a process of exclusion. The uniform associa- 
 tion of this character with the space position of the 
 end-organ prevents our separating it analytically 
 from this spatial factor, but since the character 
 must exist as a basis for the space localization, we 
 give it the name of local significance, or particular- 
 izing, local sign. Physiologically, local sign proba- 
 bly depends on the individual end-organs which are 
 active, but nothing more can be said at present/ 
 
 2. The Discrimination of Local-Sign Differences 
 
 In order that a difference in local signs may be 
 noticed, it must have a certain minimal value, 
 which, however, is variable. Similar points on the 
 corresponding fingers of the two hands can nor- 
 mally be distinguished, but if the hands are kept 
 behind a screen for some time, and the fingers not 
 stimulated, the patient tends to become uncertain 
 as to which hand is touched. The signs apparently 
 
 ^ There is a theory that local signs are muscular sensation 
 accompanying the primary sensation, or are the images of 
 muscular sensation arising from the past experience of the 
 muscular action necessary to bring the hand, or other mem- 
 ber, to the spot on the skin with which the sign is connected. 
 This theory is rather a work of supererogation, because it 
 must assume a local sign of the sensation in order that it may 
 rouse the proper muscular images; in other words, the theory 
 does not touch the problem of local significance at all. That 
 muscular sensation has a great deal to do in the discrimination 
 and systematization of local signs is another matter. 
 
140 A SYSTEM OF PSYCHOLOGY 
 
 are so nearly alike that the person forgets which is 
 which unless he has a chance to freshen his memory 
 from time to time. In general, the closer two points 
 are on the skin, the nearer alike are the local signs 
 of the sensations aroused therefrom; consequently, 
 on any part of the body there is a certain minimal 
 distance by which two simultaneously applied com- 
 pass points must be separated, if they are to be felt 
 as two. If the distance between the two compass 
 points is less than the minimum, the two points are 
 felt as one, because the difference in local signs is 
 not enough for discrimination, although the two 
 may be felt as " bigger ^^ than either alone, probably 
 because more nerve endings are stimulated in the 
 former case. 
 
 The minimal distance of separation of two stim- 
 ulating points felt as two is commonly known as 
 the " two-point threshold, and the determination of 
 this threshold is called ^* sesthesiometry." ^ 
 
 ^ Several explanations have been proposed for the physio- 
 logical side of the two-point threshold, but so far it remains 
 principally a matter for theory. A probable theory is based 
 on the fact that all dermal nerve endings are connected with 
 deeper-lying nervous structures, and that the endings con- 
 nected with one deeper organ are interspersed in the skin 
 with endings connected with other of the deeper structures. 
 Any touch stimulus, therefore, is apt to affect two or more of 
 the deeper organs, and if we assume that the local sign is 
 associated with the deeper structure rather than with the 
 dermal ending, it follows that a touch gives a combination of 
 
LOCAL SIGNIFICANCE 141 
 
 In order that practice may influence the local- 
 ization of sensation, and in order that differences in 
 local sign may be discriminated at all, it is neces- 
 sary that the signs to be discriminated shall at some 
 time occur in independence of each other. If two 
 signs or groups of signs are habitually aroused to- 
 gether, it is difficult to discriminate them; if they 
 are invariably aroused together, discrimination is 
 impossible. Touches on the opposite edges of two 
 adjacent fingers are easily discriminated; touches 
 on the apposed edges are not discriminated so read- 
 ily, especially if near the palm; and if two nor- 
 mally apposed spots are simultaneously stimulated, 
 the experience is apparently of a single touch. This 
 last phenomenon results from the fact that the 
 apposed areas are usually stimulated by a single 
 object. 
 
 In the case of the eyes, the necessity of indepen- 
 
 sensations of different local signs. The relative intensity 
 of the sensations in a given sensation-combination is accord- 
 ingly the datum for the minute localization of the mass. This 
 theory is supported by the fact that practice greatly reduces 
 the two-point threshold, and by the fact that in many cases 
 a single touch is perceived as two or even three. 
 
 The threshold varies from one millimeter or less on the tip 
 of the tongue and the finger-tips, to several centimeters on 
 the middle of the back. It bears no definite relation to the 
 intensity-threshold, or to the intensity difference threshold 
 on the different parts of the body. It is smaller on the more 
 motile portions of the body. 
 
142 A SYSTEM OF PSYCHOLOGY 
 
 dent stimulation is strikingly made evident. Nor- 
 mally, when any point in one eye is stimulated, a 
 definite corresponding point in the other eye is stimu- 
 lated in practically the same way. Hence, if under 
 experimental conditions one eye alone is stimulated 
 by light, the person is unable to tell, from that 
 stimulation alone, which eye is affected.^ This 
 peculiarity of vision is of practical importance, for 
 the stimulation of corresponding points in the two 
 eyes produces single vision; that is to say, if two im- 
 ages nearly identical in form and detail, are thrown 
 on corresponding portions of the retinae, a single ob- 
 ject is seen, whether the two images come from a 
 single "real" object or from a stereoscopic picture. 
 On the other hand, if the images of an object fall on 
 portions of the retinae not corresponding, the object 
 is "seen double.'' This effect is easily produced 
 by crossing or "walling" the eyes, or by pushing 
 on the ball of one eye with the tip of the finger (on 
 
 ^ This may be demonstrated in a dark room. Let the per- 
 son gaze at a feeble light, as a pinhole gas flame, or phos- 
 phorescent spot, having both eyes open and his head fixed in 
 position. You may bring a card in front of one of his eyes, 
 and he will be unable to tell which eye is seeing. The light, 
 if a gas flame is used, must be so dim that he cannot see the 
 card itself, and he must refrain from winking. Another 
 demonstration may be made with a pair of spectacles, one 
 lens plain and the other slightly prismatic. The person will 
 not know which image is displaced. 
 
LOCAL SIGNIFICANCE 143 
 
 the lid, of course), or by bringing a prism before 
 one eye. 
 
 Corresponding points, as the term is used in 
 psychology, may be defined as points on the two 
 retinae which are normally stimulated by rays of 
 light from a single point in an object upon which 
 the eyes converge. Corresponding areas of the 
 retinse are, accordingly, areas which correspond 
 point for point. 
 
 3. Local Sign In Auditory Sensation 
 
 It is possible that local sign plays an important 
 part in auditory sensation. According to the Helm- 
 holtz theory, pitch really reduces to local sign. If 
 each rate of audible vibration should stimulate a 
 small group of hair cells on the basilar membrane, 
 each corresponding sensation would have a specific 
 local sign, and these, differing from one another in 
 accordance with the separation of the hair cells 
 in the series, would form a linear series. The sen- 
 sations would not be localized, there being no mus- 
 cular mechanisms to assist in the associative proc- 
 ess; so the series of pitches would remain a series 
 of practically pure local signs. 
 
 Assuming that the Helmholtz theory is not cor- 
 rect, and that pitch is primarily extensity of audi- 
 
144 A SYSTEM OF PSYCHOLOGY 
 
 tory sensation, local signs may still be important 
 in connection with tones. Each pitch may come 
 to be associated with a certain local sign, namely, 
 that of the group of end-organs at which the excita- 
 tion on the basilar membrane ends. Thus, the 
 series of local signs becomes the series of symbols 
 of the extensities primarily constituting pitches. 
 Extensity itself can be estimated only approxi- 
 mately by direct observation; this is true in both 
 visual and tactual estimation, and it is possible that 
 the person of "uneducated ear" distinguishes pitch- 
 differences crudely because he attempts to judge in 
 this way. The person of "musical ear," on the 
 other hand, has possibly acquired the ability to 
 notice the local signs, which lend themselves to 
 more accurate identification, and has formed an 
 accurate system of associations between these local 
 signs and the marks of musical notation. Nothing 
 is more certain than that musical and non-musical 
 people employ different methods of estimation of 
 pitch, and that the cultivation of the "ear" is a 
 process of learning how to observe. 
 
 The immediately foregoing remarks do not apply 
 to cases of organic defect in the auditory appa- 
 ratus. There are persons who can never learn to 
 distinguish pitches accurately; some peculiarity of 
 
LOCAL SIGNIFICANCE 145 
 
 their aural mechanism doubtless prevents the ex- 
 citations from being sharply defined, a condition 
 which may properly be designated amblacousia. 
 
 4. Olfactory Local Sign 
 
 Local sign may have something to do with the 
 baffling composition of odors. Some of the peculiar 
 similarities, and differences of smell sensation may 
 really be identities and differences of local sign. 
 We must remember that we never experience the 
 local sign of dermal or visual sensation without its 
 associative connection with space, nor local sign 
 of auditory sensation apart from the corresponding 
 extensity; hence, local sign unassociated with either 
 of these factors, or associated with extensity in a 
 non-serial way, would not be naively identified. 
 
CHAPTER IX 
 
 RELATIONAL ELEMENTS IN THE CONTENT OF 
 CONSCIOUSNESS 
 
 I. General 
 
 In discussing sensations we have necessarily dis- 
 cussed the relations in which they are experienced, 
 but with reference always to the sensations. Now 
 we must focus our attention on the relations them- 
 selves, and consider them in their turn as elements 
 of content. 
 
 Just as you directly perceive sensations, so you 
 perceive relations. This red is perceived as differ- 
 ent from green; as like that other red; as brighter 
 than this one; as lying on the table; as more beau- 
 tiful than this dingy color; and so on. But it is 
 not only sensations that are involved in complexes 
 of relations; emotional content (assuming for the 
 present that it is a specific content) is equally in- 
 volved with the relational factors. 
 
 In the treatment of relation we encounter much 
 
 more diflficulty than in the treatment of sensation, 
 
 146 
 
RELATIONAL ELEMENTS 147 
 
 because of the way in which relations complicate 
 themselves in groups which seem like single rela- 
 tions; and also because of the elaborate processes 
 through which we learn to perceive certain of these 
 systems. We can develop in this chapter only the 
 general line of analysis to which this content must 
 be submitted, and amplify only enough for the pur- 
 poses of the other portions of our work which come 
 into close connection herewith. 
 
 The most conspicuous peculiarity of relation- 
 content is that it has no definitely assignable ner- 
 vous process corresponding to it. We know of no 
 " centre ^^ in the brain for the perception of relations, 
 and we do not know that it is a cortical function at 
 all. We must not suppose that perceived relations 
 depend on, or are functions of "brain-paths," or 
 "association fibres;" brain-paths represent simply 
 connections established between different factors 
 of content, by the operation of which the factors 
 function together; the physiological connection is 
 not the same thing as the experienced connection 
 or relation, and the physiological connection may 
 function perfectly whether a specific relation is 
 experienced or not. It is true that there are a 
 number of motor processes which assist in the per- 
 ception of relation, but their neural consequences 
 
148 A SYSTEM OF PSYCHOLOGY 
 
 are no more to be considered as the counterparts 
 of the experienced relations than the neural excita- 
 tion caused by the movements of the eye are to be 
 considered as the counterpart of the color sensa- 
 tion, in the obtaining of which the eye-movements 
 assist. These points will become clearer as we 
 proceed to the analysis of complex perceptions. 
 For the present we may repeat, that while we in- 
 cline to believe that there are specific brain proc- 
 esses corresponding to the relational content of 
 consciousness, as there are to sensational content, 
 the belief is as yet merely a detail of the general 
 a priori theory of the relation of nervous process 
 to experience. 
 
 The enumeration of elementary relations or 
 groups of elementary relations is a diflBcult, not to 
 say impossible, procedure in the present stage of 
 psychological analysis. The greater number of 
 familiar relations are doubtless complex. The rela- 
 tions of causality, of inadequacy, of up and down, 
 and so on, are really involutions of a number of 
 relations whose final analysis is, perhaps, not yet 
 to be made. To particularize: the relation which 
 we call causality involves the relation of succession 
 — or, perhaps, simultaneity — the relation of in- 
 variability, and, according to one view, the complex 
 
RELATIONAL ELEMENTS 149 
 
 of relations involved in the " transfer of energy/' ^ 
 Take now the factor of succession; is it a simple 
 relation? Probably not. It involves the relations 
 of betweenness and difference, with a certain re- 
 semblance, and the peculiar relation to other phe- 
 nomena involved in time. 
 
 As examples of relations which are 'probably 
 elementary we may name the following: difference, 
 identity, similarity, greater, less, betweenness, direc- 
 tion (peculiar to space), a relation peculiar to time, 
 agreement, and possibly the relations of good and 
 bad. At any rate, it is diflficult to see how these can 
 be resolved into any other relations: but the list 
 is only a suggestion. 
 
 2. Platonic Ideas and Matter 
 
 The importance of relations in the content of 
 consciousness, and in the supposed world lying 
 behind experience, has always been recognized, and 
 perhaps rather overestimated than underestimated. 
 The '* Ideas'' of the Platonic philosophy are nothing 
 less than systems of relations; at least this phi- 
 losophy is pretty good common-sense when the 
 
 * Of course, these relations are not perceived in this combina- 
 tion; that is to say, we never perceive causation outright, but 
 perceive a part and imagine the rest. 
 
150 A SYSTEM OF PSYCHOLOGY 
 
 "Ideas" are so interpreted. The philosophy 
 called "Idealism" always emphasizes the relations 
 in the content, making them the prime or essential 
 part, and the sensory factor trivial or secondary. 
 Surprising as it may seem, the apparently opposed 
 theory of "Materialism" has simply abstracted 
 some of the most universal and characteristic re- 
 lations from the content of consciousness and given 
 them the names of " Matter'' or " Substance." So, 
 from the psychological point of view, these two 
 systems are more nearly identical than opposite. 
 Empiricism, which we believe to be a more adequate 
 view, recognizes the importance of relational and 
 non-relational content, and does not attempt to set 
 either above the other. 
 
 3. Intellect 
 
 The perception of relation is commonly called 
 intellect, in both scientific and popular discourse. 
 In common language we speak of a man as being 
 "intellectual" in so far as he is quick, accurate, or 
 thorough in the noticing of relations; without re- 
 gard to his keenness of sense perception, or his emo- 
 tional capacity, or his will. Of course these fac- 
 tors of his total experience are never sundered, and 
 each is important for the others, but high develop- 
 
RELATIONAL ELEMENTS 151 
 
 ment of one does not imply development of the 
 others to the same degree. 
 
 4. The Reality of Relational Content 
 
 There are several theories of relation-content 
 which attempt to explain it away. The so-called 
 "sensationalist'^ theory supposes the relation to be 
 a sort of fusion or combination of the sensations. 
 The "motor" theory supposes that our reactions 
 to the sensory content constitute both the relations 
 of the content within itself and to other content. 
 While we do not wish to underestimate the im- 
 portance of these theories, we wish to point out that, 
 psychologically, they are only statements of the 
 conditions and consequences of the experience of 
 relations, and not explanations of the experienced 
 relations themselves. The fact remains that re- 
 lations are really perceived, and the attempt to 
 evade this by substituting for the relation a fusion 
 of sensations or a motor process is a waste of energy. 
 The relation is as much a reality as the factors it 
 relates, and we perceive it just as truly as we per- 
 ceive them. 
 
 We cannot deal adequately with relation in ab- 
 straction from the other forms of content without 
 getting outside of the field of psycholog}\ Two 
 
152 A SYSTEM OF PSYCHOLOGY 
 
 sciences — or two branches of the same science, if 
 you choose — deal specifically with relations: these 
 two are logic and mathematics, and the serious 
 student of psychology is advised to make himself 
 well acquainted with both of them, not for their 
 specific methods or results, but for their points of 
 view. 
 
CHAPTER X 
 
 IMAGES AS ELEMENTS OF CONTENT 
 I. Imagination and " Image-Types " 
 
 We have already referred to the prevalent doc- 
 trine of images as copies of sensations, or copies of 
 sensation-complexes. This doctrine is older than 
 Aristotle, who stated it pretty clearly, and who, 
 perhaps, gave it its definite formulation; and it 
 has been incorporated in some form in practically 
 every general theory of psychology since his time. 
 In modern times impetus has been given to the the- 
 ory by the introspective and experimental work of 
 Fechner and Galton, in whose steps many psy- 
 chologists have followed. 
 
 Galton alleged that there are — or may be — 
 
 images of different senses, but that images of 
 
 vision and audition are the most important in the 
 
 consciousness of adults. Galton compiled a "ques- 
 
 tionary'' which was sent to, and answered by, a 
 
 great many persons of all sorts; the object of 
 
 the questionary being to determine the kinds and 
 
 153 
 
154 A SYSTEM OF PSYCHOLOGY 
 
 relative clearness of the images possessed by these 
 persons/ 
 
 Imagination as an actual process or function 
 cannot be denied, nor is there any doubt that when 
 you imagine certain objects they will have a visual, 
 or auditory, or other sensory reference. Some psy- 
 chologists have denied the existence of images of 
 taste and smell; indicating thereby a personal 
 peculiarity, for the olfactory and gustatory features 
 of imagination are for some persons the most vivid. 
 
 Muscular imagination has received due credit 
 in the various attempts at analysis, and it has been 
 stated with apparent justification that much of our 
 "thinking," or trains of representation, goes on 
 through the activity of the "images" of spoken 
 words, and that these "images" are usually mus- 
 cular, {. e., representations or reproductions of the 
 muscular sensations which occur in speaking the 
 words. In reality, the alleged muscular images 
 may be muscular sensations. (See below.) 
 
 In accordance with the accepted view, individu- 
 als are classified under "types" corresponding to 
 the sorts of "images" they employ most constantly 
 
 ^ The intention of the questionary and Galton's views on the 
 subject of images are best obtained from his Inquiries into 
 Human Faculty. The gist may be found in James, Principles 
 of Psychology, II, 51-57. 
 
IMAGES AS ELEMENTS OF CONTENT 155 
 
 and readily. The predominance of images of the 
 muscular sensations marks one as of the "motor 
 type/' and the predominance of images of the audi- 
 tory or visual sensory sorts marks one as of the 
 " auditory type/' or the " visual type/' A person of 
 either motor or non-motor type may be of the "verbal 
 type/' i. e., may employ "images" of heard or seen 
 or spoken words. The terminological development 
 has been carried still farther, but we need not pur- 
 sue it beyond this point.^ 
 
 When we come to the actual determination of 
 "types" in accordance with the Aristotelian theory 
 of "images/' the trouble begins. Determination 
 by the simple introspection upon which the ques- 
 tionaries depend is usually unsatisfactory to the 
 patient, and still more so to the persons conducting 
 the investigation. Several auxiliary tests have been 
 devised, but they all depend on the interpretation 
 of the results by assumptions which beg the whole 
 question. 
 
 As regards the physiological processes causing 
 or corresponding to imagination, the most natural 
 theory based on the Aristotelian view is that the 
 
 ^ A person of the auditory type is sometimes called an 
 ^^audile"; of the visual type a 'Wisile." '^Tactile," "olfactile'' 
 and ^'gustile" have been used also, but are not in such high 
 repute. ** Motile" is in good usage. 
 
156 A SYSTEM OF PSYCHOLOGY 
 
 imagination process (production of the "image/') 
 is simply a revival of the sensation process in a 
 weaker form. The imagination-centres are, ac- 
 cordingly, supposed to be identical with the sensory 
 centres, and the determinative difference between 
 the imagination process and the sensation process 
 is considered to be due to the initiation of the latter 
 from the sense-organ, and of the former from some 
 other brain-centre; the currents from the periph- 
 eral organs being supposed to be more powerful 
 than the intra-cerebral discharges. This theory 
 of the brain process on which imagination depends 
 .was quite widely held a decade or two ago, but it 
 is now believed that the imagination process de- 
 pends on a portion of the cerebrum contiguous to, 
 or bordering on, the sensory area of the cortex. 
 
 We ought not to consider an "image" as a spe- 
 cific content, or a specific form of content, until we 
 have more proof of the existence of that sort of an 
 "image.'' Revived or false sensations probably 
 do occur (the "subjective" sensations of the physi- 
 ologist) but they are not what is meant by "image" 
 or imagination. Actual normal sensations from the 
 various organs may assist us in representation or 
 thinking, but they are not a new form of content 
 on that account. Imagination is a fact of con- 
 
IMAGES AS ELEMENTS OF CONTENT 157 
 
 sciousness; it is a way of being conscious of content 
 of various sorts, and not a specific content, so far 
 as we are able to determine/ 
 
 The specific sensory reference in imagination, 
 which is the basis of the Aristotelian theory, is 
 imparted in several ways, two at least of which we 
 may point out. The sensory tang may be given 
 because the object of which we are thinking was an 
 object for the sense in question when experienced 
 directly. The visible features of an object may be 
 the important characteristics for one man, and to 
 these principally he attends. Another man may 
 attend principally to the sound made by the ob- 
 ject. In recalling, or thinking, of the object, the 
 first man will recall it as a visible object, and the 
 second as an auditory object; each will think of it 
 as it impressed him. But it is an unsafe leap from 
 this bald and unexplained fact to the assumption 
 that the first man has a " copy" of the visual sensa- 
 tions and the second a '^copy^' of the auditory sen- 
 sations. 
 
 In some cases the mechanism by which the sen- 
 sory mark is given is assignable. When sensations 
 
 ^ It is convenient to use the term "image'' to designate the 
 represented content, and we shall do so, in spite of our dis- 
 sent from the general belief as to its nature. 
 
158 A SYSTEM OF PSYCHOLOGY 
 
 from a definite sense, or sensations which are the 
 normal concomitant of that sense, occur along with 
 imagination, they tend to give the imagination the 
 corresponding tang. This may be the means by 
 which the influence of the preceding direction of 
 attention to the object is realized, or it may be in 
 some cases the agency which counteracts such in- 
 fluence. The sensations in question may be from 
 the sense to which the imagination is ascribed; 
 faint sensations from the retina, i. e., of light, may 
 give the visual reference to the " image ^^; but 
 usually the sensations are from the motor apparatus 
 functionally connected with the sense-organ. 
 
 In thinking of a visual object, e, g,, of an illumi- 
 nated sign, there are movements of accommodation 
 and convergence of the eyes, if the person is of the 
 "visual'' type. In thinking of the sound of an 
 orchestra there are changes in tension of the mus- 
 cles in the tympanum of the ear, or in the neck- 
 muscles. If you fix your eyes on a point on the wall 
 you will probably find it difficult to call up the pict- 
 ure of a ship under sail; let the eyes wander freely 
 and the picture comes up readily. Fixate steadily 
 a square of mosquito netting, and the picture will 
 probably not come at all; this is because the net- 
 ting offers an excellent object for steady fixation. 
 
IMAGES AS ELEMENTS OF CONTENT 159 
 
 Some persons find a great decrease in facility of 
 visual imagination when the eyes are under the in- 
 fluence of atropine; in the case of these persons the 
 sensations of accommodation are important in mark- 
 ing the image. 
 
 If you can readily recall or imagine odors try the 
 following experiment: take a deep breath, and have 
 some one else name an odor just as you begin to 
 exhale slowly through the nose; you will find that 
 you do not get the image until you begin to inhale, 
 and probably not then if the inhalation is slow. 
 Sniff, and the image appears at once. Certain 
 persons, whose taste images are extremely vivid, 
 cannot get them unless the tongue is allowed to 
 move. 
 
 A type of experiment which is noteworthy may 
 be exemplified in the following way: put the vocal 
 organs in position to say " Ah,'^ and, holding them 
 so, try to think or image the word " soap-bubble," 
 or "parsimonious." The word will, in most cases, 
 not "think" fluently. Such results have been held 
 to demonstrate that the images of the words are 
 "motor." It really shows only the close connec- 
 tion between the muscular sensations from the vocal 
 organs and the imagining of the words. 
 
 The very ease with which individuals have been 
 
160 A SYSTEM OF PSYCHOLOGY 
 
 convinced that what they before believed to be 
 "visuar^ or " auditory ^^ images were really '^ mus- 
 cular/^ as a result of experiments like the one just 
 described, is in itself sufficient to raise a serious 
 presumption against the Aristotelian theory. Like- 
 wise, the maintenance by certain persons, among 
 whom are trained psychologists, that they never 
 have any images such as Galton and others describe, 
 is a significant circumstance. If the sensory ref- 
 erence is not intrinsic, but dependent on the me- 
 chanical interpretation of attendant sensations, these 
 anomalies are quite explicable. 
 
 2. The Function of Imagination 
 
 Although the discussion of imagination belongs 
 logically to the later chapters of this book, we must 
 anticipate somewhat, in order to describe the be- 
 havior of the content when apprehended imagina- 
 tively, and the way in which that behavior modifies 
 the total content in perception. 
 
 We are naively disposed to think of imagination 
 as a play of fancy which may be amusing and in- 
 teresting, but hardly as subserving the more prac- 
 tical and prosaic processes of thought. As a mat- 
 ter of fact, this latter is just what imagination does. 
 Imagination is the basis of memory and of all rea- 
 
IMAGES AS ELEMENTS OF CONTENT 161 
 
 soiling processes, and upon it depends the percep- 
 tion of objects in the world about us. 
 
 Whatever has been perceived may be imagined 
 in much the same form. Having seen a lion and 
 heard it roar, I may on some subsequent occasion 
 imagine a lion of the same appearance, and with 
 the same sort of a roar. The content is indeed 
 never exactly the same in imagination as it was in 
 perception, but the difference may be unimportant. 
 This approximate repetition of a former content is 
 the reproductive function of imagination, and we 
 speak of it simply as reproductive imagination. 
 According to the Aristotelian theory the content 
 is an approximate copy of a former sense-con- 
 tent. 
 
 On the other hand, content may be imagined in 
 forms and combinations quite different from those 
 of the original perception, and hence we are able 
 to imagine things which, strictly speaking, we have 
 never perceived. Sensory content experienced in 
 one perception may creep in with content of another, 
 or certain sensory factors may be eliminated from a 
 former content. New relations may be introduced, 
 and old relations modified. In consequence of 
 these changes we have not only a general modifica- 
 tion by which the content of all experience tends to 
 
162 A SYSTEM OF PSYCHOLOGY 
 
 lose its individuality, but also the special ease which 
 we call creative imagination. 
 
 One who imagines a perfectly "impossible'' 
 animal, a griffin or a "goop'', is imagining a con- 
 tent composed or built up of the elements of a mass 
 of content which he has previously perceived. It 
 is only necessary to modify the human figure by 
 changing certain contours in ways which are al- 
 ready familiar, and the "goop" is invented. Any 
 one of us could imagine all the details separately, 
 or in other combinations; otherwise we should not 
 appreciate the "goop;'' the notable feat was in 
 imagining them combined. In poetry, the content 
 suggested is such as we can all imagine — if the 
 poetry appeals to us — but the poet has combined 
 it in new ways. The scientist, in discovering a 
 new principle, is able to imagine what he has never 
 perceived, by imagining old content in new combina- 
 tions; then, if his imagining has been successful, 
 he is able to use new methods or arrange new con- 
 ditions of experiment, so that what he imagined be- 
 comes now perceived, or he is able to demonstrate 
 his results logically. 
 
 In creative imagination the creator is aware of 
 the modification of the content. Along with the 
 rest of the content he has the peculiar factor which 
 
IMAGES AS ELEMENTS OF CONTENT 163 
 
 we call newness, or novelty. He is aware that his 
 content is a new combination. But in the general 
 modification of content which we mentioned above, 
 the person is less apt to be aware of the changes. 
 The fisherman who magnifies into a three-pounder 
 the minnow which escaped; the student who re- 
 lates the hard-luck story of how he "failed'^ in an 
 examination through no fault of his scholarship; 
 are in many cases quite sincere, and base their tales 
 on imagined content which has undergone progres- 
 sive "improvement^^ since it was experienced in 
 perception. 
 
 A distinction has frequently been made in the past 
 between the image and the idea. The image was 
 supposed to be the special content in imagination, 
 and the idea to be that to which the image referred, 
 or which it meant; or else the idea was supposed 
 to be both the image and its meaning taken to- 
 gether. This view can be expressed by saying that 
 the image present to consciousness means some- 
 thing (some former content) which is not " present.'* 
 The introduction of the content image does not 
 seem to answer the question as to how consciousness 
 is able to grasp what is not "present*' to it, and it 
 seems that instead of trying to dodge the issue we 
 might as well admit that we can be conscious of 
 
164 A SYSTEM OF PSYCHOLOGY 
 
 content which is not presented: in which case the 
 copy-image is a useless supposition. 
 
 If we do not postulate a specific image-content, 
 the distinction between image and idea is of no 
 practical value unless we are willing to make it in 
 the way in which it is made in every-day language. 
 We do commonly discriminate in our use of the 
 two terms, using "idea" in a general sense, and 
 " image" to signify a form of idea in which the sense 
 factors perceptible in a single physical object or lim- 
 ited group of objects, are especially emphasized. 
 Thus when I "think" of the pyramids of Egypt, I 
 usually have a content which combines vague ele- 
 ments of geometrical form with more definite frag- 
 ments of representations of their probable builders 
 (drawn of course either directly or indirectly from 
 pictures and written descriptions), with a "feeling" 
 of great distance from me, and with some actually 
 presented muscular sensations which normally ac- 
 company the lifting of a heavy weight. These are 
 not the only factors, but they are typical of what 
 the idea of the pyramids involves. It is possible 
 to think of the pyramids in another way, in which 
 the monuments themselves, as perceptible objects, 
 become more prominent, and their relations to 
 other things become less important. They are 
 
IMAGES AS ELEMENTS OF CONTENT 165 
 
 then thought of as concrete objects in which color, 
 form, and weight-content become predominant, and 
 the factors of distance, antiquity, construction- 
 problems, and personal and racial connections are 
 minimized. It is useful to call the content of the 
 former way of thinking an idea, and the content of 
 the latter an imager but this is not to be taken 
 as an accepted scientific usage, and the two terms 
 must be used with caution. 
 
 So far we have been speaking especially of the 
 sensation-content in imagination; but relations are 
 also imagined. A composite sensory content is 
 presented in a complex of relations, and when we 
 imagine a similar content it also is set in and per- 
 meated by similar relations. We have shown above 
 that in what we have called an image a limited 
 group of sensory content may be important, as 
 against the importance of a wider group in what we 
 have called an idea, and we should also point out 
 that in the idea the relations which enter into the 
 content are to a large extent external to the central 
 feature, while in the image the relations within the 
 central factors of content are the most important, 
 the external relations sinking into insignificance.^ 
 
 * The increasing difficulty of arousing ^'images/* which fre- 
 quently accompanies prolonged scientific training, is partly 
 
166 A SYSTEM OF PSYCHOLOGY 
 
 In the instances given the central content is con- 
 stituted by the features intrinsic to the pyramids 
 themselves, as perceptible objects, and the ex- 
 ternal relations are the relations to geography, 
 engineering, the peculiarities of the builders, etc. 
 
 It is possible to have an imaginative content in 
 which the relations are the central feature, and the 
 sensory factors are purely incidental. Such a con- 
 tent is a further development of what we have above 
 described as the idea, in the common parlance, and 
 is properly called an abstract idea, or concept} 
 
 The three types of content in imagination are 
 therefore what we may call the image, the idea, and 
 the concept: and we maintain that, as content, ab- 
 stracted from the mode of being conscious of them, 
 they involve only sensation and relation.^ 
 
 The difference between the image of a horse and 
 
 the idea of a horse ought to be already clear to the 
 
 reader. In thinking of a horse of such a size and 
 
 due to the habits of ideating engendered by that training. 
 The scientist habitually apprehends all data in relation to 
 other data, and loses to a greater or less extent the power to 
 isolate which is characteristic of the artist. 
 
 * The concept is sometimes identified with the Platonic Idea, 
 and it may seem that we have committed ourselves to this 
 view; but that is not quite the case. 
 
 2 This statement is to be taken with the question previously 
 raised; whether feeling is ever strictly imagined: but if feel- 
 ing is a form of sensation, the statement is accurate without 
 qualification. 
 
IMAGES AS ELEMENTS OF CONTENT 167 
 
 color and attitude, and with that sort of qualifica- 
 tion only, you "have an image"; but if you are 
 simultaneously conscious of the usefulness of that 
 animal as a beast of burden, or his importance as 
 an enemy in an encounter, or his evolutional re- 
 lation to other animals, or his need of hay and 
 grain, you "have an idea/' Now just carry this 
 differentiation a step further, and let the particular 
 horse dwindle in significance, and the relations 
 to burdens, oats, and so on, become more emphatic, 
 and you "have the concept '^ of a horse. 
 
 The preceding illustration makes apparent an 
 important fact about concepts, and one which is 
 sometimes overlooked. There are as many dif- 
 ferent concepts of a horse as there are different in- 
 dividuals who conceive it — in fact, each individual 
 has many concepts of the equine species — differing 
 according as they emphasize this or that set of 
 relations; and yet in the large sense the concepts 
 agree, since an animal which will agree with the 
 concept of the zoologist or the artist will also satisfy 
 the concept of the hostler. (The specimen which 
 is ranked high under one concept may, however, 
 be ranked low under the other.) 
 
 While the various concepts of a horse held by 
 different individuals pretty generally agree in func- 
 
168 A SYSTEM OF PSYCHOLOGY 
 
 tion, there are other sorts of concepts which do not. 
 The concept which one man has of morality, or of 
 a moral being, is often incommensurable with the 
 concept held by another man on nominally the same 
 subject. This is probably because the concepts 
 of neither are adequate; that is, neither has grasped 
 a really definite and coherent system of relations. 
 
CHAPTER XI 
 
 RETENTION, MEMORY, AND RECALL 
 I. Retention 
 
 As we have indicated already, one general con- 
 dition of imagination is the previous perception of 
 what is imagined, although the content in imagina- 
 tion does not necessarily have the same form and 
 combination which it had in the former perception 
 or perceptions. One who has never perceived 
 light — one blind from birth — cannot imagine color,^ 
 and a similar limitation applies to any other sen- 
 sation, because sensation cannot be built up from 
 anything else. As with sensations, so with rela- 
 tions; if they are not first apprehended, they can- 
 not be conceived, although we may form concepts 
 involving relations which have not previously been 
 experienced in the exact combination in which they 
 occur in the concept. A person who had never 
 witnessed the transformation of a substance from 
 solid to liquid, and vice versa, might conceive of 
 
 * The blind man, by noting what others say about the ob- 
 jects he perceives through touch, may be able to talk intelli- 
 gently about their colors, and may not even know that he 
 does not know what color is. 
 
 169 
 
170 A SYSTEM OF PSYCHOLOGY 
 
 liquefaction and solidification, but he could do so 
 only if he had noticed the difference between the 
 two states of substance, and had noticed modifica- 
 tions of other sorts. 
 
 The dependence of imagination on previous per- 
 ception, although an undoubted fact, may not be 
 so rigid as it is represented in such statements as 
 those we have made above. Just as there are in- 
 stinctive tendencies to actions which the individual 
 has not learned to execute — tendencies due to the 
 structure with which the individual is endowed by 
 virtue of his place in the animal kingdom — so there 
 may be instinctive tendencies to be conscious in 
 particular ways, due to the nervous constitution of 
 the individual and not to his experience. Until 
 this possibility is excluded we can merely say that 
 the dependence of imagination on the previous 
 experience of the individual in the way described 
 above is the general or usual fact. 
 
 The dependence of imagination on perception is 
 given the functional name of retention. In some 
 way, the effects of the past experience or content 
 have been preserved and so the present imagina- 
 tion made possible. We do not know exactly 
 what it is that is retained, but psychologists are 
 accustomed to designate it plurally as traces. The 
 
RETENTION, MEMORY, AND RECALL 171 
 
 experience leaves its traces, and through some 
 activity initiated or facilitated by these traces 
 the content is later revived as an image. Some 
 theorizers claim that these traces are only phys- 
 iological; modifications in the brain and its ap- 
 pendages; others insist that there are mental traces 
 also. 
 
 On the whole, the doctrine of mental traces seems 
 to be not an explanation of the dependence of im- 
 agination on perception, but a symbolic statement 
 thereof which adds nothing to our knowledge on 
 the subject. 
 
 The first notable feature of retention is the fact 
 that it varies with the individual. One man, hav- 
 ing experienced a certain content, retains it for a 
 long time; another, under similar conditions, quick- 
 ly loses the effects of what he experiences. This 
 difference shows plainly in memory; we find the 
 one man able to recall isolated bits of past experi- 
 ence with ease and accuracy, while the other man 
 requires all sorts of aids in order to recall his simi- 
 lar experiences. The differences show also in the 
 creative imagination; the wealth and facility of im- 
 agery of some individuals as against the poverty and 
 sluggishness of others is due in part to the extraor- 
 dinary way in which all sorts of experiences stick 
 
172 A SYSTEM OF PSYCHOLOGY 
 
 in the minds of some, and the difficulty with which 
 they are retained by others. A great deal of individ- 
 ual variation is due to the factors we are to take up 
 next; but after allowance is made for them there 
 seems to be a residue of personal diflFerences as yet 
 unanalyzed. 
 
 In the second place, experiences which are 
 strongly impressed, that is, are strongly attended to, 
 or are repeated several times, are more firmly fixed 
 and retained than are experiences not having that 
 advantage. This accounts for one sort of individual 
 peculiarit}- two persons may observe the same 
 phenomena, and afterwards each will be able to 
 recall more fully the things to which he w^as specially 
 attentive. A man fails to recall the color and style 
 of the costume of the woman to whom he talks for 
 half an hour, while his wife after one glance would 
 be enabled to recall these details and a great many 
 more; the man does not attend to sartorial feminine 
 details, although he undeniably sees them. The 
 effects of repetition are too familiar to need ex- 
 emplification. 
 
 In the third place, all effects of experience tend 
 to disappear with the lapse of time. One might say 
 that (to use an ancient analogy) the mind is like a 
 tablet of wax or clay, upon which experience writes. 
 
RETENTION, MEMORY, AND RECALL 173 
 
 The firmer the wax and the deeper the engraving, 
 the more permanent the inscription; nevertheless, 
 all inscriptions tend to become in time illegible 
 through the slow process of disintegration of the 
 surface of the tablet. Writing that is to last as long 
 as the tablet must be scratched in deep at the first, 
 or else the lines must be often retraced. 
 
 In many cases, content whose traces are ap- 
 parently obliterated is really retained. As we say 
 in common terminology, things forgotten for years 
 may return to memory with great vividness. The 
 causes of this abeyance are obscure; in part it de- 
 pends on associative factors, as will be made clear 
 in the next chapter, but over and above the part 
 played by association there is an unexplained factor 
 in the variation in facility with which the traces of 
 past experience, or content, become active. This 
 slight obscurity is an important basis of the pseudo- 
 scientific theories of " subconsciousness" with which 
 we will have to deal later. We must remember that 
 retention is only a name for the fact that a past 
 content is subject to being re-experienced in imagi- 
 nation, and that the only proof that a content is 
 retained is in its being imagined; and, conversely, 
 if any content of former experience is imagined, 
 that is prima facie proof that it has been retained. 
 
174, A SYSTEM OF PSYCHOLOGY 
 
 even if the period between the original experience, 
 and the reproduction is fifty years. 
 
 What has been once experienced may not return 
 to consciousness in imagination, but may be effec- 
 tive in another way. If you learn the lines of a 
 poem to-day, you may have "forgotten" them by 
 next month, and be able to repeat none of them. 
 Yet, you will find that the relearning of the poem 
 requires less time and energy than the first learning; 
 this is largely a matter of association, but not al- 
 together. 
 
 The retention of the various impressions is facil- 
 itated, and in fact the retention of complex content 
 is made possible, by association. Under that head- 
 ing, as well as under the headings of memory and 
 recall, retention must be further discussed. 
 
 2. Memory 
 
 The term memory is used in psychology in prac- 
 tically the same sense as in common parlance, but 
 certain biologists are in the habit of using the term 
 in another way; a practice which has brought about 
 a great deal of confusion and unnecessary conflict 
 of statement. If an animal acts upon any stimulus 
 in a way which is the result of previous stimulations; 
 if his conduct or experience (assuming that we know 
 
RETENTION, MEMORY, AND RECALL 175 
 
 something about his experience) is based on the 
 experience of the past, it is said by some writers 
 that the memory of the past experiences or stimula- 
 tions is demonstrated. There would be no objec- 
 tion to this use of the term to designate the influ- 
 ence of the past nervous processes on those of the 
 present, if it had not been used so long to mean 
 something more specific. 
 
 Specifically, memory means the consciousness of 
 any content, with the coincident consciousness that 
 the content has been experienced before {i. ^., rec- 
 ognition), and at some more or less definite date. 
 If I remember a train wreck in which I was a par- 
 ticipant, I am conscious of it now, (in the way of 
 reproductive imagination), and also conscious that 
 it happened awhile ago; I may be aware of the 
 exact period at which it occurred, or I may not, but 
 I at least locate it in a certain period of my past. 
 
 It will perhaps occur to the reader that the 
 greater part of my past experience, however much 
 it may modify my present experience and activity, 
 is not remembered. For example: my reading 
 and writing are the result of a number of definite 
 experiences of my early life, yet I do not remember 
 the content of these experiences, nor can I remem- 
 ber them if I try. If some one calls you by name. 
 
176 A SYSTEM OF PSYCHOLOGY 
 
 you will reply; yet in ninety-nine cases out of a 
 hundred you do not remember your name at the 
 time. You have formed certain fixed habits in 
 regard to the particular sound to which you answer, 
 but in few cases does it occur to you that you have 
 heard the name in the past. 
 
 Many times we reproduce in imagination past 
 content, without being aware that it is past content; 
 the experience is mere reproductive imagination, 
 not memory. The facility with which non-reminis- 
 cent reproduction occurs is at the basis of a great 
 deal of plagiarism in literature; an author imagines 
 a situation or sentiment which is really an exact 
 or approximate reproduction of something he has 
 previously read in another author^s writings, but 
 he does not remember it, and so the trouble be- 
 gins. A striking example of this sort of reproduc- 
 tion is found in a short story or miracle-tale by a 
 well-known American author, who relates that the 
 story came to him in a sort of dream at night. The 
 idea and elaboration of the tale are so similar to that 
 of one of Tolstoi^s short stories as to raise the pre- 
 sumption that the American author, having read 
 Tolstoi's "Two Pilgrims," at some earlier time, 
 reproduced it in an altered form, and failed to 
 recognize it. 
 
RETENTION, MEMORY, AND RECALL 177 
 
 The important thing about memory is the factor 
 of recognition by which the reproduced content is 
 enriched. We have said enough to indicate that 
 this factor involves or depends upon certain feat- 
 ures of perceived time; its further treatment will 
 accordingly be deferred to the chapter in which time 
 is discussed. 
 
 3. Recall 
 
 Given the fact that a content once perceived 
 may be subsequently imagined; to which fact in the 
 abstract we give, as said above, the name retention, 
 we inquire why the content is imagined — called 
 back, or recalled, as it were— at one time rather 
 than another; or we may even wish to know why or 
 how it is recalled at all. A part of the mechanism 
 of recall is understood, if imperfectly. 
 
 In the first place, the very fact of retention im- 
 plies a tendency to come back. Whatever content 
 has been experienced may by virtue of that fact 
 alone return later to consciousness. The expres- 
 sion '* spontaneity of the image ^' has been applied 
 to this recurrence-tendency, the expression figuring 
 the image as an entity with an active force pressing 
 it toward the field of consciousness. We might 
 develop the analogy by likening consciousness to a 
 
178 A SYSTEM OF PSYCHOLOGY 
 
 stage, of varying area, but strictly limited, on which 
 a vast crowd of players are seeking to enter. Some 
 of these players are continually sent on and oflF the 
 stage by directing agencies, but if these agencies 
 cease to operate, or leave vacancies, the images hav- 
 ing the most energy at the moment will thrust 
 themselves on. It is especially in dreams and rev- 
 eries that content seems to revive in the way de- 
 scribed by this highly artificial analogy. 
 
 In the second place, content revived in memory 
 or imagination tends unmistakably to disappear 
 soon after its entry into the field of consciousness. 
 It may be kept before consciousness for varying 
 periods of time through the effect of associative 
 factors, or in pathological cases the image may 
 monopolize consciousness for long intervals; but 
 normally it tends to fade soon after appearing. In 
 the terms of the analogy, the players seem to be ex- 
 hausted by the effort of their appearance before the 
 foot-lights, and need to retire to some psychologic 
 greenroom for long periods of recuperation. If it 
 were not for this fortunate shortness of vitality of 
 imaged content, the stream of thought would soon 
 cease to flow, as in the pathological cases above 
 mentioned. 
 
 The most important factor in recall is association. 
 
RETENTION; MEMORY, AND RECALL 179 
 
 The content of past experience is so linked together 
 that given any perception or imagination-content 
 before consciousness it tends to bring in certain 
 other content. This Unkage is designated as asso- 
 ciation. Because association is of wider interest 
 than is its function in recall, we shall give it a chap- 
 ter by itself. 
 
CHAPTER XII 
 
 ASSOCIATION 
 I. The Principles of Association 
 
 Association is the organization of experience, 
 by virtue of which the various kinds and parts of 
 content constitute a whole; it is the functional inter- 
 connection of the objects of experience as we find 
 them; not a force or activity. The statement of 
 the principles or laws of association is by no means 
 an explanation of anything, but simply a convenient 
 summary of observed facts. 
 
 I. The Principle of Integration. 
 
 The total content of consciousness under nor- 
 mal conditions is unified or organized into a unity. 
 The various factors which we distinguish are given 
 not as distinct elements fortuitously collocated, but 
 as inseparable parts of the total content. This 
 organization or integration has two directions: (1) 
 Organization in simultaneity, and (2) Organiza- 
 tion in succession. 
 
 (1) We find organization at any given instant in 
 
 the content of consciousness. If we liken the total 
 
 180 
 
ASSOCIATION 181 
 
 content to a rope, a cross-section of the rope repre- 
 sents the state of the content at any given time. If 
 we analyze this cross-section of content we find it 
 reducible to the factors already enumerated (sen- 
 sation and relation, with feeling and possibly image; 
 the association as content, is relational). We do 
 not suppose that these elements originate individ- 
 ually and then unite, like chemicals thrown into a 
 beaker; we consider them as arising in the com- 
 binations in which they are found, and likewise 
 declining; by both processes modifying the com- 
 plexes in which they exist. 
 
 We find the cross-section of content made up of 
 several smaller unities — again like the rope, al- 
 though the rope strands are merely contiguous, 
 while these complexes are more or less intercon- 
 nected, the same element often forming an element 
 of several. If you are looking at a rotating color- 
 wheel, and also thinking of the end of the hour, the 
 content of your consciousness is composed of several 
 subdivisions somewhat like the following: A, A 
 complex of color and sound sensations with rela- 
 tions and images (which you call the color-wheel) 
 with certain emotional factors, perhaps interest, 
 perhaps ennui. These tend to form a special 
 group, possessing an internal coherence not shared 
 
182 A SYSTEM OF PSYCHOLOGY 
 
 with the other groups described below, although the 
 emotional element, and perhaps some sensational 
 elements, may be common. B. Your thinking of 
 the end of the hour depends on the function of a 
 specific group of content (mostly imaginative), both 
 sensory and intellectual, with emotional coloring, 
 perhaps of desire, impatience, or aversion, or per- 
 haps the ennui above mentioned. Imagery of the 
 length of time yet to elapse, of the occupations to 
 commence, of the heat of the sun outside, and so on, 
 may supply the nucleus of this division of content. 
 C A third group, or set of groups, is composed of 
 bodily feelings, with certain sights and sounds not 
 involved in the first mentioned groups — the mov- 
 ing of shadows across the wall; the buzzing of a 
 fly; the pressure of the clothing on the skin; the 
 warmth or chilliness of parts of the body; visceral 
 sensations, thirst, and so on; with, perhaps, certain 
 emotional coloring not germane to the other groups. 
 Each of the three groups mentioned is separable 
 under scrutiny into several subgroups^ The anal- 
 ysis, or a stage in the analysis, of group C is obvi- 
 ous. In group A the treatment is not so easy. 
 Perhaps we find the visual factors forming the nu- 
 cleus of one subgroup, and the auditory that of an- 
 other, but in some cases it seems that the auditory 
 
ASSOCIATION 183 
 
 and visual factors are united with each other as 
 firmly as auditory with auditory or visual with 
 visual. 
 
 In many cases we find, before reaching the ulti- 
 mate elements, peculiar small groups which are 
 called fusions, in which several sensations of the 
 same mode can be discriminated. Thus, the hue 
 of the revolving wheel may be a fusion of several 
 primary colors; purple is a fusion of red and blue; 
 the taste of the lemon-drop in your mouth is a fusion 
 of sweet, sour, and a slight bitter. It is a question 
 whether we ought not to include under the term 
 ^^fusion'^ combinations not of the same mode, as 
 warmth and touch sensations, taste, and smell. 
 
 In applying the name " fusion,'' we mean to im- 
 ply that while these combinations function as units 
 in practically the same way as do elementary sen- 
 sations, they can be perceived as complex, by atten- 
 tive observation. In this analysis the complex con- 
 tent changes: it is a commonplace that the taste of 
 lemonade is not simply the taste of lemon jplus the 
 taste of sugar, but has an individuality of its own. 
 This change is readily made intelligible if we re- 
 member that in analyzing a fusion we bring in or 
 emphasize relations which were not previously in 
 the content, or else were not vivid; and that in ex- 
 
184 A SYSTEM OF PSYCHOLOGY 
 
 periencing separately the elements of the fusion, as 
 the sour and the sweet, we have in the contents a 
 different relational nexus, and perhaps, also, differ- 
 ent imaginative sensory factors from those present 
 when the fusion is experienced even with attempt 
 at analysis.^ 
 
 (2) We have said that content is organized not 
 only in simultaneity, but also in succession; it is 
 integrated in longitudinal as well as in cross-section. 
 The present content is essentially connected with 
 that of the future and of the past. Moreover, each 
 group, subgroup, and element has an actual life 
 history. No sensation, for example, comes into 
 existence instantaneously; it rises, reaches a maxi- 
 mum of intensity, and then falls back. So a cross- 
 section of any portion of the content of consciousness 
 at any time represents only a stage in its develof>- 
 ment. In this the analogy to the rope comes up 
 again; the rope is made up of fibres, each having a 
 definite length, short as compared with the length 
 of the rope; but here also the analogy fails, as there 
 
 ^ The student may be surprised at the way in which the 
 ^individuality" of the lemonade taste may be made to de- 
 crease. Take a glass of lemon-juice solution and a glass of 
 sugar solution, of such strength that when equal quantities 
 of each are mixed in a third glass a good lemonade results. 
 Then taste the three solutions in alternation, making careful 
 comparisons. 
 
ASSOCIATION 185 
 
 is nothing in the rope to represent the temporal 
 development of the subgroups. 
 
 It is clear that psychological research has a two- 
 fold problem at any point which it attempts to in- 
 vestigate from the side of content: first, to analyze a 
 given content, and, second, to trace the development 
 thereof. The solution of the second problem is 
 much more difficult than that of the first, for it 
 really involves the solution of the first for a number 
 of successive stages. If I wish to study emotion 
 of a certain type, for example, I must not only 
 analyze such emotion at a given moment or stage, 
 but must also make or assume analyses at several 
 moments in its life history, in order to understand its 
 development and the longitudinal connection of its 
 elements. The same treatment should eventually 
 be applied to the total stream of consciousness; by 
 performing adequate analyses at enough points in 
 the life history of the individual we might get a 
 comprehensive view of the psychic life. 
 
 II. The Principle of the Middle Term, or Medi- 
 ate Association. 
 
 Two contents or factors in content which are not 
 strongly linked directly may be linked each to a 
 third term, or they may be linked through several 
 intermediaries: and this mediate linking of the two 
 
186 A SYSTEM OF PSYCHOLOGY 
 
 may be more important practically than the direct 
 associations with the intervening term or terms. 
 If M and N are two factors in content which are so 
 far apart in time that M has practically faded out 
 before N commences to rise, but if P occurs while 
 M is vivid, and is still eflFectively on the stage when 
 N becomes vivid, the three may form a fibre in suc- 
 cessive association, uniting M with N through P. 
 The name ^*Bud^^ and the jaw movement of gum- 
 chewing are, perhaps, associated in your experience 
 not because you have heard the one and seen the 
 other at the same time, but because each has been 
 associated in simultaneity with some other feature 
 or features of an individual. Other examples will 
 readily occur to the reader. Emotional content is 
 especially apt to form a third term in this way. 
 Those contents which have been experienced to- 
 gether under the influence of strong emotion are 
 more firmly associated thereby, other things being 
 equal, and what has been experienced with a certain 
 quality of emotion at one time is associated medi- 
 ately with what has been experienced at another 
 time under the same sort of emotional conditions. 
 
 III. The Principle of Intellectual Association. 
 
 The association of two elements or groups of 
 content is stronger in so far as a definite relation 
 
ASSOCIATION 187 
 
 or system of relations is perceived as subsisting be- 
 tween them. If I notice that two things are simi- 
 lar or dissimilar in some regard, or if I notice that 
 one immediately follows the other, or if I perceive 
 or imagine that one is the cause of the other, or 
 that they are spatially related in a certain way, 
 these things are more strongly associated than if 
 the relations had not been noticed. 
 
 IV. The Principle of Redintegration. (Principle 
 of Reinstatement; Principle of Associative Recall.) 
 
 When any content appears in imagination or 
 apprehension there is ipso facto a probability that 
 the other contents associated with it will appear 
 also: in other words, a total content tends to be 
 reinstated as soon as a part of it is introduced. 
 The events are analogous to what happens when 
 you try to pull a weed out of a tangle in the water; 
 you find that you pull out a large quantity of others 
 which are ensnarled with it. 
 
 There are several ways in which this revival of 
 past content through association may take place. 
 
 (1) The associated factor may reappear in the 
 same organization as before. If you meet to-day a 
 person whom you met yesterday, you may be again 
 conscious of some of the circumstances in which 
 you met him before. The stage setting, as it were. 
 
188 A SYSTEM OF PSYCHOLOGY 
 
 in which he was placed is revived as soon as he 
 reappears. In repeating the words of a poem the 
 imagery and emotions appropriate to the words and 
 phrases which have been associated with them come 
 up in proper synthesis. Moreover, the successively 
 associated factors are repeated in their former 
 sequences; the words of the poem are recalled nat- 
 urally in the order in which they have been linked 
 in the text of the past experience. The series of 
 words forming the poem are, as the result of the 
 past experience, associated in a whole in which 
 imagery and emotional coloring bind them together 
 in multiple bonds. Words and phrases in one 
 portion of the poem are so linked by intermediate 
 terms and directly with phrases in other portions, 
 that having once commenced the recitation of the 
 poem we are in little danger of being carried off 
 the thread into something else. But if we were 
 restricted to associations between simultaneous or 
 immediately successive factors, we would be apt, 
 when we have recalled the line " lead kindly light,*^ 
 to finish it up " of other days around me,^' and still 
 more apt to finish " Yes, that was the reason (as all 
 men know), in this kingdom by the sea, that the 
 wind came,^' by adding *^up out of the sea, and said, 
 'O mists, make room for me.'" 
 
ASSOCIATION 189 
 
 In poetry the enveloping rhythm furnishes a con- 
 tinuous bond in association which would operate to 
 prevent transitions such as those we have just sug- 
 gested; in some cases, however, the transitions from 
 one text to another would not alter the rhythm, 
 especially if it is a matter of diflFerent bits from the 
 same poem. In prose, of course, there is nothing 
 but normal mediate associations to prevent the va- 
 rious texts we have memorized from being "pied'' 
 in recall. 
 
 The rhyme furnishes in some poetry an addi- 
 tional means of association. Certain sounds are 
 given by their position in the rhythmic structure, 
 and, by repetition, an especial emphasis and dura- 
 tion in consciousness, so that there is immediate 
 association between one rhyme word and the ones 
 preceding and following it. Rhymes, alliterations, 
 and all such devices are to be considered as means 
 for the production of associative bonds, tying the 
 stanzas together in a more unified whole than 
 would otherwise be achieved. They are not aes- 
 thetic ends, but are mechanism for the production 
 of ends aesthetic, or even practical, as in the jingles 
 by which we manage to fix elusive facts of history. 
 
 (2) The time order of the former content may 
 be modified in the recall. The setting in which I 
 
190 A SYSTEM OF PSYCHOLOGY 
 
 saw the person yesterday may not recur when I see 
 or think of him to-day, but may come in afterward. 
 On the other hand, things which were experienced 
 in succession may be imagined or remembered simul- 
 taneously, or when one is perceived the others are 
 recalled simultaneously with it. After the child has 
 experienced the sight of the medicine, followed by 
 the taste, and perhaps subsequent nausea, the mere 
 sight of the proffered mixture arouses coincidently 
 the other factors. 
 
 (3) Very frequently contents which have been 
 mediately associated become immediately associ- 
 ated through the dropping out of the middle terms 
 or term. Seeing a load of coal put in suggests the 
 sifting of ashes; hearing a huckster announcing 
 soft crabs suggests finding a gold watch; yet the 
 various terms which in the beginning mediated the 
 association do not occur to me until afterward, if 
 at all. This sort of modification of association by 
 the elimination of terms is so common that it 
 largely escapes our notice. 
 
 V. The Principle of Relative Strength. 
 
 We may say that the possibility of the reinstate- 
 ment of any content through association with an- 
 other content present to consciousness is propor- 
 tional to the strength of the association, and that 
 
ASSOCIATION 191 
 
 therefore if a given factor, M, is associated with two 
 contents, P and Q, which are too different to come in 
 together, the one most strongly associated with M 
 will come. (The so-called principle of conflicting 
 associations.) But if P is associated with M, and 
 also with K, which is just disappearing, and with S, 
 which is present throughout, whereas Q is asso- 
 ciated only with M, P may be brought in, in spite of 
 the stronger connection of M with Q than with P; for 
 the other associations assist in reviving P. (This 
 is sometimes called the co-operation of associa- 
 tions.) We may illustrate by the poetical frag- 
 ments given above: the Longfellow poem may be 
 much more familiar to you than the one by Poe, 
 and hence " the wind came up" more strongly asso- 
 ciated with "from out of the sea" than with "out 
 of a cloud by night." In that case, if some one 
 should repeat to you " the wind came up, " alone, 
 you would finish the line Longfellow- wise. When 
 the earlier lines of the poem of Poe are given you 
 too, you finish the line accordingly because of the 
 co-operating associations of "out of a cloud by 
 night" with these earlier lines. 
 
 The concept of "strength" of association must 
 be admitted to be very vague. After all, it is 
 constructed, like the concept of retention, from the 
 
192 A SYSTEM OF PSYCHOLOGY 
 
 fact that things do come back, and that they come 
 back in specific ways, as we have been trying to 
 show. When we say that M is more strongly asso- 
 ciated with P than with Q, we mean simply that 
 unless some other factor operates, M will call up P 
 rather than Q, 
 
 The strength of any association depends, like the 
 retention of content, upon the vividness with which 
 the associated factors are impressed, and on the 
 repetition of the impressions in succession or 
 simultaneously. This needs no extended discus- 
 sion here. The strength of the association is also 
 increased by each recall through the association; 
 the oftener M calls up P, the more readily it will 
 do so. 
 
 2. Voluntary Recall 
 
 We often make the attempt — successful or not — 
 to recall some definite content. This attempt, or 
 performance, seems at first inspection to be absurd. 
 If I am not conscious of a given content how do I 
 know what it is? The recall is actually set in 
 motion, or we attempt to set it in motion, by a proc- 
 ess which is naively described as ^'Thinking of the 
 things we know to be associated with the required 
 content," trusting to the associations to bring the 
 
ASSOCIATION 193 
 
 required content before consciousness. But we 
 ask: How do I know what is associated with the re- 
 quired content, if I do not know what that content 
 is ? And how do I manage to bring up the things 
 associated with the required content ? 
 
 The fact is that these contents are already there, 
 or some of them are, and it is their presence that 
 brings the desire for the sought factor. Some fac- 
 tor, M, comes up, which is in a certain relation to 
 something else, and yet the present factor and the 
 relation do not bring up the missing one. So I 
 attend to some other factor suggested by M, to see 
 what it will suggest; if this does not suggest some- 
 thing satisfying the relation, it may suggest some- 
 thing which will make the proper suggestion. For 
 example : I see across the room a man whose name 
 I do not remember. The fact that I am approach- 
 ing him calls up the impending salutation, and the 
 relation of the visible man to a name; yet the name 
 is not recalled. The appearance of the man recalls 
 Mr. Blank, at whose house I was introduced to the 
 man; I hold the idea of Mr. Blank and the meet- 
 ing in consciousness, and these factors recall the 
 joke Mrs. Blank made on the man's belying his 
 name; still the name does not appear, although I 
 am getting "warm.'' This incongruity of man and 
 
194 A SYSTEM OF PSYCHOLOGY 
 
 name, if attended to, may suggest his voice, and 
 then the name — Singer — may come up at once. 
 This is a typical instance of voluntary recall, and 
 the only voluntary element is the "holding of the 
 attention on certain content," to get the maximal 
 effect from its associations. 
 
 Sometimes the factors on which the attention is 
 held in voluntary recall are relations. Thus, in 
 trying to think of a man's name the relation of 
 rhyming with something may come up, and by at- 
 tending to that relation a rhymed word will in 
 many cases appear, and assist in the final solution 
 of the problem. Sometimes we start with a num- 
 ber of relations and seek that which will fulfil 
 them; start with a concept, in short, and let it de- 
 velop into an idea. This is conspicuously the case 
 in the solution of riddles. 
 
 3. The Probable Physiological Basis of Association 
 The exact physiological bases of association are 
 as yet unknow^n. We assume that there are some 
 processes in the brain corresponding to these func- 
 tions, but what they^are or where they are located 
 has not yet been discovered. It has been quite the 
 fashion to ascribe association to the formation of 
 " brain-paths, " lines of conduction from one cell or 
 
ASSOCIATION 195 
 
 group of cells to another; but this was intended 
 only as a picturesque metaphor; for, taken liter- 
 ally, it would imply a special cell or group of cells 
 for each idea capable of being associated with an- 
 other, or other absurdities which no psychologists 
 or physiologists entertain. Some theorizers have 
 assumed the existence of a special association cen- 
 tre in the frontal lobes, but so far there is not much 
 real evidence for the theory. 
 
CHAPTER XIII 
 
 PERCEPTION 
 I. The General Nature of the Content in Perception 
 
 We have already indicated that perception com- 
 prises more than intuition or direct apprehension; 
 that is to say, that the content in perception in- 
 cludes more than sensations and relations. Per- 
 ception^ is the consciousness of a content which in 
 usual cases includes (1) present sensations, (2) 
 present relations interwoven with the sensations 
 and other content, (3) imaginative content, and 
 (4) emotional factors. With regard to the third 
 category, we ought to say at once that by far the 
 most important thing in the imagined portion of 
 the content of perception of adults is conceptual. 
 The merely sensuous imagery may play a part, but 
 it is relatively unimportant in comparison with the 
 systematized relationships in which the intuited 
 content is placed. 
 
 Suppose I stand some distance from a railroad 
 
 track and observe a passing train: I obtain a com- 
 
 ^ ''Perception'^ is used loosely in common discourse for any 
 sort of understanding or comprehension. We are using it here 
 in a strict, technical sense. 
 
 196 
 
PERCEPTION 197 
 
 plex perception-content which it is worth our while 
 to analyze. In the first place, there are the ele- 
 ments of light and color. The locomotive, the cars, 
 the smoke, the trees which form the background, 
 are presented as an aggregate of many hues and 
 shades. At the same time are presented sensations 
 of other modes; the panting of the locomotive and 
 roaring of the wheels and shriek of the whistle, the 
 smell of the smoke, and the trembling of the ground. 
 These sensations are only a small part of the total 
 content. Not only do I notice the spatial relation 
 of the colors — that the dark and shiny locomotive 
 precedes the red cars, that the smoke hangs above 
 the trees and spreads out — but I notice the likeness 
 of the smoke to the clouds, the contrast between the 
 red and the green of the trees, and so on. More- 
 over, I am conscious that it is a passenger train, 
 which means, probably, that I imagine people 
 within it: I imagine the wheels turning, although I 
 cannot see their rotation; I image other features 
 according to my habits of thought. Certainly, 
 whatever I perceive of a sensory nature, beyond a 
 few patches of color and a few sounds and smells 
 and the vibration, is imagined. 
 
 More important than the intuited content, or the 
 imaged sensory content, is the fact that I recognize 
 
198 A SYSTEM OF PSYCHOLOGY 
 
 the object as a railroad train; I am aware of its 
 relations to iron tracks, stations, transfer of pas- 
 sengers, purchasing of tickets, and numberless other 
 details, some of which, like the passengers inside, 
 may be imaged, but the greater number of which 
 are not. On account of this conceptual synthesis 
 of the content, my train as I perceive it is vastly 
 different from the train a savage would perceive 
 from my view-point, although he would experience 
 the same sorts of sensations and the same pre- 
 sented relations as I do. So, too, the train as the 
 content of the railroad man or of the farmer would 
 differ largely from mine, because in each case a 
 different set of relations would be emphasized by 
 the individual's past experience, and be aroused to 
 unite as a concept with the intuited factors. 
 
 The function of the concept in perception is 
 sometimes called apperception. The concept and 
 the imaged sensory factors connected with it are 
 called the apperception mass, and the directly ap- 
 prehended sensations and relations the apperceived 
 factors. These terms are now falling into disuse. 
 
 The concept is built, developed, and extended, 
 by experience. Any new perception is apt to mod- 
 ify the concept which functions therein. The 
 first time an individual rides on a train, which be- 
 
PERCEPTION 199 
 
 fore he has merely seen — and heard — from a dis- 
 tance, he apprehends a lot of new relations which 
 thereafter recur in the concept. If perchance he 
 sees some one run over, the train is perceived with 
 new elements of relation, and henceforth all trains 
 will be perceived in the light of a concept modified 
 by those relations. 
 
 Changes in the concept may take place also 
 without perception; when the sensory content 
 which fills out the concept and makes it concrete 
 is only imaged. When, for example, I speak to 
 you of trains, you imagine them; your concept at- 
 taching itself to the sensory content which you call 
 up, just as if it were apprehended in reality. If 
 then I tell you of the running over of some one, or 
 explain the problems of maintaining equilibrium on 
 curves, or providing suflBcient elasticity to allow 
 starting and stopping, the imaged content takes in 
 new details, and the modified concept will govern 
 your next perception of a train. 
 
 We may reach a stage of conceptual development 
 in which concepts are modified without the neces- 
 sity of filling in, even imaginatively, with sensory 
 content. New relational factors are learned, usu- 
 ally by inference, and these are amalgamated with 
 the concept already in existence: or the process 
 
200 A SYSTEM OF PSYCHOLOGY 
 
 may be one of elimination, certain supposed prop- 
 erties of a certain thing being found not properly 
 belonging to it, and the concept being contracted 
 accordingly. It is difficult to show instances of 
 this purely intellectual modification of concepts in 
 every-day life (although it undoubtedly occurs 
 there), but in science the process is clearly exhib- 
 ited. The atom, for instance, was conceived with 
 an approach to adequacy, and as new facts 
 were learned the concept was modified accordingly, 
 until it has become vastly different from that held 
 by scientists twenty-five years ago. Yet sensory 
 imagination plays little part in this readjustment, 
 being more a disturbing factor than otherwise. In 
 less abstruse cases, where imagination might have 
 a role, the scientist economizes energy and in- 
 creases accuracy by leaving it out.^ 
 
 The development of perception is, therefore, in 
 reality, the development principally of conception. 
 The sensory factors are very simply controlled, and 
 
 ^ We may distinguish three types of conceptual modifica- 
 tion, which possibly correspond to stages of mental develop- 
 ment. These stages are: (1) The perceptual, (2) the concrete 
 imaginative, and (3) the conceptual modification of con- 
 cepts. Possibly animals are restricted to the first type, but 
 of this we have no proof. In the case of adult human beings 
 the first type rarely occurs pure, but undoubtedly many per- 
 sons never attain in the slightest to the third type. 
 
PERCEPTION 201 
 
 only a small amount of experience is needed to 
 make them practically as perfect as they ever may 
 be. The individual is endowed by his parentage 
 with his sensory apparatus; it is developed in part 
 through the demands made upon it by his experi- 
 ence, but largely through the general development 
 of the body, just as the hair grows. A little prac- 
 tice is needed to direct, focus, and converge the 
 eyes properly, but these adjustments develop in 
 the individual largely of themselves, demanding 
 only use to fix the development. The child of a 
 few years is equipped sensationally as well as he 
 ever will be, and much better than he will be in 
 adult life. 
 
 2. Perception, Illusion, and Hallucination 
 
 Perception may be "right" or "wrong." The 
 incoming sensory content may be united with the 
 proper concept, or it may be united with an egre- 
 giously inappropriate concept. The former case, 
 where the perception is " right/' we are accustomed 
 to call true or normal perception, and the latter case 
 we call illusion. To take an extreme case: a 
 sheet is hanging on a bush in the dark, and some 
 one seeing it unites the visual appearance with his 
 concept of a ghost: his perception is illusory, yet 
 
202 A SYSTEM OF PSYCHOLOGY 
 
 he may receive sensory and relational intuition- 
 content practically agreeing with that of another 
 person who unites it with the appropriate concept 
 and perceives truly. 
 
 The freshman who looked at the page-heading 
 in my copy of the Critique of Pure Reason and 
 exclaimed in amazement, "Transcontinental dia- 
 lect! What in the dickens is that?/' probably re- 
 ceived from the printed words sensations not very 
 different from those I received; but since one, in 
 reading, notices but a part of the letters in a word, 
 imagining or dispensing with the rest, the fresh- 
 man's unfamiliarity with the transcendental dia- 
 lectic resulted in the noticed letters calling up the 
 concepts associated with them in his experience. If 
 you see a man on the street, and say, " Ah, there is 
 Richard Roe; I must speak to him about that 
 book," and then find on overtaking him that it is 
 not Roe at all, but John Doe, who scarcely re- 
 sembles Roe on close scrutiny, your mistake lies in 
 that to certain sensory factors intuited you added 
 the imagined facial expression, etc., of Richard 
 Roe, and the concept you have formed of that 
 gentleman. 
 
 The contrast between perception and illusion 
 disappears when we examine them closely. The 
 
PERCEPTION 203 
 
 extreme cases we have instanced, where the con- 
 cept is hopelessly inadequate, are few in compari- 
 son w^ith the cases in which the inadequacy is not 
 so pronounced. Many persons at the present 
 time conceive a trolley-car as dragged along by the 
 trolley, vaguely supposing that the "current'' in 
 the wire carries the trolley along with it, as the 
 cable "grip'^ is carried by the cable. When such 
 a person has found out the way in which a street- 
 car is actually propelled, the content of his percep- 
 tion of a car is appreciably changed; and yet the 
 error is of no practical consequence to the mistaken 
 man as long as he does not attempt to fill a posi- 
 tion as a carman. On the other hand, a slightly 
 inadequate perception of a car as regards its speed, 
 or of an invalid as regards his condition, may have 
 the most serious consequences. Perhaps the truest 
 statement would be that none of our conceptions and 
 perceptions are quite adequate, but some are near 
 enough to adequacy for practical purposes. 
 
 One special type of "false" perception has re- 
 ceived the name of hallucination. In this the in- 
 tuited sensational factor is reduced to a minimum, 
 or at least is not of any practical consequence in 
 the total perception. The essential sensory fac- 
 tors are all supplied by imagination, but the com- 
 
204 A SYSTEM OF PSYCHOLOGY 
 
 plex is mistaken for, or at least has the apparent 
 character of, reality. Hallucinations occur to al- 
 most all of us in what we call dreams, and some- 
 times in waking life, but waking hallucinations are 
 usually attendants of mental disease. 
 
 Hallucination and illusion are to be distinguished 
 from pseudo-hallucination and pseudo-illusion. 
 Pseudo-hallucination is often found in dreams, 
 where the content has the semblance of perception- 
 content, except that the dreamer is distinctly con- 
 scious that it is a dream, and not real. So, in wak- 
 ing life, there often occur experiences which have 
 many of the marks of perceptions, but which we 
 know are imaginations. There is something about 
 the experience or the content which gives the lie 
 to the impressiveness of the other factors. The 
 semblance of reality produced in pictures and on 
 the stage is to be classed as pseudo-illusion. The 
 familiar geometrical illusions, on the other hand, are 
 true illusions in most cases, for the semblance has 
 all the characteristics of true perception-content, 
 in spite of the fact that we know it is not. We have 
 to do here with a percept and an additional con- 
 cept which do not fuse or unite. ^ 
 
 * Hallucinatory perceptions must be distinguished from 
 subjective sensations, secondary sensations, and after images, 
 
PERCEPTION 205 
 
 3. The Determination of Perceptual Truth and Falsity 
 
 The discussion of illusion brings us to the con- 
 sideration of the criterion of truth in perception. 
 Here we find two questions. First: When, and 
 in how far, is a perception true? and second: How 
 do we decide whether a sensation is true or suffi- 
 ciently near the truth? As a matter of fact, the 
 grounds on which we decide practically the truth 
 of a perception are by no means those which would 
 be assumed for the philosophical justification of 
 the decision. The statement of the grounds on 
 which we actually judge the validity of a perception 
 does not cover the grounds on which a thoroughly 
 adequate determination could be based. 
 
 There are two practical tests of truth and falsity. 
 The first may be called the social test If my per- 
 ception is illusory or hallucinatory, it is in most 
 cases shared by no one else, and, conversely, if it is 
 shared by no one else it is an illusion or hallucina- 
 tion. If, for example, you see a translucent hand 
 beckoning from the door-way, and others in the 
 
 and from the phenomena in certain pathological cases where, 
 for example, the smell of a certain odor is persistently present 
 to consciousness, without the normal stimulation. All these 
 cases are of present sensations due to definite sensory processes 
 in the sense mechanism. 
 
206 A SYSTEM OF PSYCHOLOGY 
 
 same room see nothing of the kind, you know that 
 you have an hallucination, and if you are wise will 
 consult a competent physician. If you hear some 
 one talking, whereas other persons in the same room 
 hear only the trickling of water from a leaky fau- 
 cet, you conclude that you were mistaken in your 
 perception. 
 
 The social test is not thoroughly trustworthy. 
 Frequently your perceptions are right and those of 
 your companions wrong. The obstinacy of one 
 man in insisting that he hears the crying of a child, 
 when the others are equally confident that the 
 sound is the moaning of the wind in the trees, 
 saves the child's life. It is possible, also, for a 
 number of people to be simultaneously illuded, as 
 a number of " authentic '^ ghost stories show. Per- 
 sons of the same general type and training placed 
 in similar circumstances will perceive in much the 
 same way, and there is nothing surprising in the 
 fact that a number of people will bring up 
 wrong concepts of approximately the same sort, if 
 the conditions are about the same for all. For 
 example, if several persons are expecting to see a 
 ghost, that is, if the appropriate concepts and images 
 have been recently and vividly attended to, the 
 sensational data which suffices to revive and unite 
 
PERCEPTION 207 
 
 with the ghost-concept of one may suflGice for the 
 others. 
 
 The important practical test is your own further 
 experience. If the pin you see on the floor can be 
 picked up, and stuck into something, it is still con- 
 sidered as a pin. But if it fails to give all the sen- 
 sations (visual, tactual, etc.,) expected from a pin, 
 you conclude that your first perception was wrong. 
 If the man you take for an acquaintance does not 
 respond to your words in the way you expect, you 
 conclude that after all he is some one else. And 
 so on. A large part of the perceptions of our ex- 
 perience are proved inadequate by the further 
 transformations of the content, and are revised 
 accordingly. 
 
 The philosophical question as to the real nature 
 of truth arises from the consideration of the possi- 
 bility that we may be more or less deluded in our 
 daily life without becoming aware of it. So many 
 times we act on a misconception, and yet our action 
 fits the case suflSciently well, that we wonder if any 
 of our tests give us anything really fundamental. 
 One school of modern philosophy insists that any- 
 thing is true in so far as it works, and no farther; 
 that truth is just the fact of standing the practical 
 test. An older conclusion is that a perception 
 
208 A SYSTEM OF PSYCHOLOGY 
 
 may be true or false quite regardless of my action 
 on it; that when I perceive a bottle in the road in 
 the moonlight, it either is or is not a bottle, even 
 if I do not get off my horse to investigate it. But 
 no one has been able to propose a really satisfactory 
 explanation of the nature of truth. 
 
 4. The Causes of Illusion 
 
 The immediate cause of illusion is not different 
 from that of normal or correct perception. The 
 imaginative content which is in the one case in- 
 adequate, and in the other case adequate addition 
 to the intuited factors, is in either case revived 
 through association. It is not necessary that the 
 reproduced content should be previously associated 
 with the directly presented content in the perception; 
 it may be called up through an associative linking 
 with some other content factor in consciousness. 
 Thus, you take the shadow by the roadside for a 
 robber, not because that particular impression of 
 light and shade is essentially connected with the 
 figure of a man, but because your consciousness is 
 already filled with imagination of brigands and 
 hold-ups. In commoner cases, you misread a 
 printed word, or mistake spoken words because 
 something you have just read, or heard, or thought 
 
PERCEPTION 209 
 
 of is associated with the idea corresponding to the 
 misreading or mishearing. 
 
 In normal perception, you make out the cold 
 cylinder you grasp in the darkness of the garden 
 to be the hose because you imagined it to be there 
 (or possibly you conceived it as there) before you 
 touched it; if you did not, it gave you a shock, and 
 the perception came more slowly after additional 
 factors had been experienced. Waiting for the 
 train, the distant whistle is easily recognized, when 
 otherwise it would have passed for one of the feat- 
 ures of the storm roaring about you. In reading, 
 the words are recognized by the appearance which 
 you sense in an inadequate way, assisted by the 
 images excited by the preceding words and sen- 
 tences. 
 
 Association directly between the reproduced 
 factor and the intuited factor of the perception con- 
 tent is an important feature in the greater part of 
 our perceptual life. Experience is a constant suc- 
 cession of perceptions whose contents are unex- 
 pected until they occur, and the imaginative parts 
 whereof are not contributed from the just-preced- 
 ing, or contemporaneous contents. The seen or 
 otherwise intuited impressions call up the imagery 
 associated with them from the past, and it may be 
 
210 A SYSTEM OF PSYCHOLOGY 
 
 adequate to the occasion, or it may not. The notes 
 of the flute which fall upon your ear from the next 
 house are perceived as the sound of that empty- 
 toned instrument although you had not been think- 
 ing of flute or flute-tone until these notes smote 
 your ear. The spider crawling on your knee may 
 have been entirely unexpected until he met your 
 eye, and yet you perceived him immediately. The 
 sound of some one shutting the door, which turns 
 out finally to have been the creaking of your chair, 
 was not perceived wrongly because your conscious- 
 ness was filled with the idea of some one entering 
 the room, but because that particular sound was 
 associated in your past experience with the other 
 sensations from shutting a door. 
 
 In determining the definite perception based on 
 a given intuited content, the factors we have earlier 
 described as governing the " strength ^^ of associa- 
 tion and likelihood of recall play a large part. If a 
 certain sense-content is strongly associated with 
 certain other factors, either through repeated ex- 
 perience of them in conjunction, or because of the 
 recency or impressiveness of such an experience, 
 that sense-content will tend to call up those factors 
 regardless of whether they are the right or wrong 
 things at the time. Moreover, the mere recency. 
 
PERCEPTION 211 
 
 frequency, and vividness of past experience of a 
 given content which is at all capable of assimilation 
 to intuited content, increase the probability of its 
 being revived by the intuited content, in accordance 
 with the principles of retention and recall. The co- 
 operation of associations is also of importance in 
 many cases; if you notice the peculiar noise, and 
 at the same time notice the movement of your body 
 in your chair, you will be less apt to perceive the 
 opening of the door, although the sound alone might 
 have called up that illusory perception. 
 
 Fine discrimination of sensations favors correct 
 perception. The creaking of the chair was not 
 precisely like the sound made by the opening of the 
 door, so that the presence or absence of the illu- 
 sion depends, in part, on the delicacy with which 
 auditory differences are apprehended. In so far 
 as sensory complexes seem alike they tend to call 
 up the same associated factors, because the features 
 of the contents which are noticed are associated 
 with these factors; and in as far as the contents are 
 discriminated, that is, in as far as other factors than 
 the common ones are noticed, they tend to call up 
 their special associates. 
 
212 A SYSTEM OF PSYCHOLOGY 
 
 5. Space Perception 
 
 In the analysis of perceived space we find one of 
 our knottiest, but most interesting, problems. The 
 history of philosophy includes much discussion of 
 the question whether space is an actual external 
 reality (the a posteriori theory), or whether it is 
 something mental — a "form'' in our minds, sup- 
 erposed on the world in perceiving it — (the a priori 
 theory). The discussion of this question has really 
 little to do with experience or its content, being 
 based on conventional definitions of "mind" 
 "external world" and other terms, much as the 
 moves in a game are determined by rules; but it 
 has had an unfortunate influence on attempts at 
 psychological analysis. 
 
 We must start from the fact that there is in our 
 perceived content a factor which is practically the 
 "space" of common parlance (not the "space" of 
 the mathematician or metaphysician), and attempt 
 to analyze this factor. 
 
 The line of opposition has been drawn in the 
 past between the "nativistic" and the "genetic" 
 theories of space perception. In large part, the 
 controversy between those holding these two views 
 has been an unwitting discussion of the a priori- 
 
PERCEPTION 213 
 
 a "posteriori question, complicated by the question 
 whether we have to learn, as individuals, to perceive 
 space, or whether we perceive it instinctively. In- 
 volved in the controversy is the still further ques- 
 tion whether space as perceived is sui generis, or 
 whether it is constructed in some way out of ele- 
 ments which are non-spatial. The genetic view 
 insists that we learn to perceive space, and is usually 
 a prioristic: the nativistic view holds to instinctive 
 space perception, and may take either the a priori 
 or the a posteriori tack. The apriorists, of course, 
 believe space to be sui generis; the aposteriorists, 
 whether nativistic or genetic, may take either side 
 of this latter question. 
 
 While our business here is primarily the analysis 
 of the space-content, keeping clear of the meta- 
 physical problems as far as possible, we shall not 
 hesitate to assume that we as individuals learn by 
 experience to perceive space in its detailed form, 
 although a part of our perceptive ability is native 
 or instinctive. This, however, is nothing but as- 
 sumption, and our suggestions as to the probable 
 development of space-content must be understood 
 in the light of that fact. 
 
 The characteristic thing about the space-world 
 is that everything in it stands in definite and peculiar 
 
i 
 
 214 A SYSTEM OF PSYCHOLOGY 
 
 relations to everything else therein; relations which 
 are analogous to some found outside of the space- 
 world, but which are characteristically different 
 from them. These space relations we recognize 
 when we refer to distance, direction, contiguity, 
 intervening objects, and other characteristic features 
 of the spacial factor of our content. 
 
 In addition, space depends on the relation of 
 magnitude, which is found also in non-spatial con- 
 tent, and likewise upon the universal relations of 
 similarity, difference, etc.; but these are not, prop- 
 erly speaking, factors in space. 
 
 Space relations can be intuited only as founded 
 upon the extensity-character of sensation. Whether, 
 having been perceived, they may be imagined — 
 may form part of a conception — without the imaged 
 sensation, is another, and questionable, matter. 
 Our own opinion is that when space is strictly con- 
 ceived it loses its true content-character, and be- 
 comes merely a mathematical system of relations 
 w^hich is marked by a correspondence to the space 
 of perception and imagination. 
 
 The difference between extensity and extension; 
 between the mere sensational volume and space, is 
 this: as soon as you begin to discriminate extensive 
 
PERCEPTION 215 
 
 parts within a sensation, or mass of sensation, you 
 have space. The perception of the extensity as 
 divided; as having one part set off against another 
 part — the perception of extensity in relation — is 
 the perception of extension or space. 
 
 In gustatory and olfactory sensation we have no 
 distinction of extensive parts, and in consequence 
 no gustatory or olfactory space. These sensations 
 may be more or less massive or extensive, but that 
 is all. The same is true of sounds; the volume of 
 a tone may change, but there is no space-character 
 to the tones because there is no relation of extensive 
 parts of any tone, but simply a relation of extensities 
 of different tones. We may say, with great proba- 
 bility of correctness, that if we were restricted to 
 these sensations there would be no space in the con- 
 tent of our perceptions. 
 
 Vision and touch supply the necessary conditions 
 for the perception of a space-world. In these senses 
 we have extensive magnitudes which are not homo- 
 geneous, but which are differentiated by local signs. 
 One extensive portion of sensation, (if of sufficient 
 magnitude), is immediately different from other por- 
 tions, and hence we may believe that an animal hav- 
 ing only one of these sorts of sensation, or any sort 
 of sensation in which extensity and local signs are 
 
216 A SYSTEM OF PSYCHOLOGY 
 
 developed, perceives space, although the space 
 may not be very complex.^ 
 
 The fundamental spatial relation seems to be 
 betiveenness. This differs essentially from the mere 
 intermediacy of other continua, although we com- 
 monly represent all sorts of intermediacy in the 
 spatial terms; as, for instance, a series of values by 
 points on a straight line. The perception of be- 
 tweenness in space may depend on the perception 
 of time; that is, when an object moves over the 
 skin or retina it occupies a certain position between 
 the moments at which it occupies other positions; 
 and by repetition of these experiences the spatial 
 betweenness of the various points is brought to 
 perception. Yet it is not at all certain that the spa- 
 tial betweenness may not be perceived as directly 
 as the temporal. 
 
 The perception of the intermediacy of local signs 
 in an extensity continuum furnishes the primary 
 datum of space. The relation of direction may be 
 reducible to these factors plus the implication of 
 motion; but this is a mere conjecture. The oc- 
 currence of the same local sign in two different series, 
 as a stimulus moves in actually different directions 
 
 ^ For the "musical" ear the series of pitches may therefore 
 form a rudimentary space-system. 
 
PERCEPTION 217 
 
 over the sensitive surface, may be the first clew to 
 difference of direction. 
 
 Distance is primarily the amount of difference 
 in local sign between two points; this corresponds 
 roughly to the least number of local sign differences 
 discriminable between the two points. You will 
 find for example, on the skin, that two points appear 
 separated by an interval approximately propor- 
 tional to the number of different points discrimin- 
 able in the straight line between them. This is 
 why the points of a pair of compasses or scissors a 
 quarter of an inch apart appear more widely sep- 
 arated on the finger-tip than on the arm, and still 
 more widely separated on the tip of the tongue. 
 Of course, if no points are discriminable between 
 two given points, they will be perceived as one 
 point.^ 
 
 So far we have considered only the factors which 
 enter into space of two dimensions, that is, of sur- 
 face. An animal endowed with touch or sight, or 
 both, but with no sensation of movement, would 
 
 ^ An interesting experiment may be made by drawing the 
 points of a pair of compasses across the face from side to side, 
 allowing one point to pass above and the other below the 
 mouth, and observing the apparent variation in the separation 
 of the points when the distance between them is constant. 
 Also, try drawing the points abreast down the arm, or down 
 the leg from knee to ankle. 
 
218 A SYSTEM OF PSYCHOLOGY 
 
 have experience of a space in which sensations ap- 
 peared, moved about, and vanished; but the re- 
 moval of the stimuli from the skin would simply 
 cause the sensation to be unperceived, and stimuli 
 at greater or less distances from the eye would sim- 
 ply give sensations of less or greater area. The 
 animal with touch and sight would probably per- 
 ceive two spaces, for the chance that he would iden- 
 tify his tactual and visual surfaces is slight. But, 
 given the power of sensations from the movements 
 of the sense-organs and members of the body, and 
 unified space perception in three dimensions be- 
 comes possible. 
 
 It is scarcely probable that muscular sensation 
 by itself can give space-content. The only between- 
 ness of such sensation is the temporal betweenness, 
 and its function in the production of space-content 
 can be only secondary. But it does help to de- 
 velop our space-content in a very important way, 
 the outline of which is probably as follows. By 
 moving one member (as the finger), over another 
 member (as the hand), we acquire the connection of 
 the temporal series of muscular sensations with the 
 motion or series of positions in tactual space on the 
 hand, and the continuous stimulation of one spot 
 on the finger. By moving the finger over some ex- 
 
PERCEPTION 219 
 
 ternal object we obtain the same series of muscular 
 sensations, with the same sort of stimulation of the 
 finger. The result is the conception of a surface 
 over which the finger moves in the same way as it 
 moves over the hand; the temporal series of mus- 
 cular sensations having become associated with a 
 series of positions in space, (tactual sensation ex- 
 tension), muscular series which do not rouse the 
 tactual series suggest series of positions in addition to 
 those in the tactual field; hence space is immensely 
 multiplied in extent. At the same time, since the 
 same series of muscular sensations may condition 
 a movement in tactual space and a movement in 
 Tisual space, and the connection of two such series 
 is invariable, the two are identified as a mere matter 
 of mental economy; that is to say, tactual space is 
 identified with visual space. 
 
 If the above were the whole story, space as per- 
 ceived would still be a matter of surface only. The 
 feature of tactual-muscular perception which brings 
 "depth" into space is this: a series of muscular 
 sensations not accompanied by a series of tactual 
 sensations (the finger moving through the air) may 
 end in conjunction with a definite tactual sensation, 
 and in fact we can put no limit to the number of 
 different series which may terminate in conjunc- 
 
220 A SYSTEM OF PSYCHOLOGY 
 
 tion with a sensation of practically any local sign. 
 Here we have the primary factor in tri-dimensional 
 space; series of positions, of which one or at most 
 two lie in the given surface. Finding no definite 
 limit to the number of series terminating at any 
 position, the step to the conception of an infinite 
 number is easy. In visual perception we have 
 similar conditions, in that certain series of muscular 
 sensations correspond to series of positions in the 
 visual field, while certain other series correspond 
 to a single position. 
 
 It is not necessary to assume that the individual 
 has to go through the stages from " blooming buz- 
 zing confusion^' through two-dimensional space per- 
 ception to tri-dimensional. It is not necessary to 
 suppose that the infant's perceived space is other 
 than tri-dimensional from the first. But without 
 doubt the space relations are at first rather vague 
 and simple, until the discrimination of local signs, 
 and their connection with muscular sensations 
 clears up and amplifies the content spatially as the 
 child's motor processes develop and receive exer- 
 cise. If, however, the individual does not perceive 
 space instinctively, it seems quite possible for the fac- 
 tors mentioned to bring the necessary relations to his 
 consciousness, and build up the percept of extension. 
 
PERCEPTION 221 
 
 We may describe a few experiments illustrating 
 the co-ordination of visual and tactual space with 
 muscular sensations. Hold before one eye a prism 
 with large side, but narrow base, turning the base 
 either to right or to left, and closing or covering the 
 other eye. Better still, have a prism or a pair of 
 prisms set in a spectacle frame, thus permitting the 
 use of both eyes, and supporting them while leav- 
 ing the hand free. On looking through the prism 
 at any small object placed before you on the bare 
 table, the object will in appearance be displaced to 
 one side. Keeping your hand out of sight by your 
 side until the moment of trial, make a rapid stab at 
 the object with you forefinger. You will find that 
 the finger strikes to one side of the goal. Keep on 
 trying, and, in the course of a few minutes, you 
 will find yourself able to hit the mark fairly well. 
 Now remove the prism from the eye and repeat 
 the trials, and you will find that you now make 
 misses on the other side of the target, and require 
 some practice to get back to your normal co-ordina- 
 tion again. 
 
 Suppose, looking through the prism, you touch 
 your hand or arm with a pencil; or, better still, 
 have some one else do the touching. The tactual 
 and the visual spaces no longer seem the same, 
 
222 A SYSTEM OF PSYCHOLOGY 
 
 but a little practice will bring them together as 
 before. 
 
 An interesting experiment, named after the 
 philosopher who gave the earliest extant descrip- 
 tion of it, "Aristotle's Experiment/' has been re- 
 ferred to in 2 of Chapter IX. If the first and second 
 fingers are crossed and the Y so formed is rubbed 
 in the crotch with a pencil or rod, the rod feels 
 double. The effect is still more surprising if the 
 crotch of the crossed fingers is touched with the tip 
 of the tongue or point of the nose; you can hardly 
 fail to have the distinct perception of a forked 
 tongue or bifurcated nose. But even this illusion 
 can be destroyed by continued stimulation under 
 visual control. 
 
 Although space relations may be in the first in- 
 stances — and later also — intuited just as are sensa- 
 tions, they are in a great part of our perceptual ex- 
 perience purely ideal; they are reproduced in the 
 content through their association with intuited or 
 reproduced sensory data. This is true, at any rate, 
 in the visual perception of space, and there we know 
 rather definitely what the factors are which are 
 associated with the relations. 
 
 Direction, that is, the angular estimation of space 
 position with regard to the body or eye as a centre. 
 
PERCEPTION 223 
 
 is indicated by retinal local sign, in conjunction with 
 the muscular sensations coming from the ocular 
 apparatus and the muscles of the body, especially 
 the neck. Simultaneous stimulation of different 
 spots of the retina gives localization in different 
 directions, as do successive stimulations of one spot 
 if certain muscular sensations intervene. By the 
 specific muscular sensations intervening between 
 the successive occupancy of one spot by two stimuli 
 the angle between the two is estimated; that is, 
 the relative direction of the two from the eye. 
 
 Distance from the eye is indicated by a number 
 of signs, which may be effective singly or in co- 
 operation. These factors are (1) light and shade 
 (chiaro-oscuro), (2) definition and color (aerial per- 
 spective), (3) size (linear perspective), (4) angular 
 perspective, (5) convergence and accommodation, 
 (6) binocular disparity, and (7) parallax. 
 
 (1) Objects in advance of others throw shadows 
 across them, the direction of the shadows depending 
 on the direction of the source of light. Often the 
 depth of shadow corresponds to the degree of re- 
 lief. A curious effect may be obtained from an in- 
 taglio, obliquely lighted; it will appear at times to be 
 a cameo, with the light coming from the opposite 
 side. A little study will show you that the lights 
 
224 A SYSTEM OF PSYCHOLOGY 
 
 and shadows of an intaglio do correspond approxi- 
 mately with those of a cameo, if the two are lighted 
 obliquely from opposite sides. How large a part 
 chiaro-oscuro plays in visual perception may be il- 
 lustrated by making a negative print of a portrait, 
 and comparing it with the positive print. The re- 
 versal of light and shade makes the picture surpris- 
 ingly different. 
 
 (2) Objects at a considerable distance from the 
 eye are blurred through the irregular refraction of 
 the air, and they likewise are tinged with color by 
 the atmosphere. "Dim distance'' and "purple 
 peaks," indicate the practical importance of this 
 factor. The blurring of distant objects is easily 
 noted in nature, and its representation is frequent 
 in paintings. The absence of the customary tint- 
 ing distortion, as in the Rockies, where the air is 
 fairly pure and homogeneous, gives rise to ludicrous 
 mistakes on the part of those unused to such con- 
 ditions. The author once heard a tourist insist that 
 he could easily walk in an hour to the base of the 
 mountain range at which we were gazing; the range 
 being really more than forty miles distant. 
 
 (3) As an object recedes from the eye its retinal 
 image becomes smaller; all lines connecting char- 
 acteristic points in the image become shorter. It 
 
PERCEPTION 225 
 
 follows, that if we know what size the object would 
 appear when near, we have in this some information 
 as to the distance from the eye at any time. 
 
 (4) The form of an angle gives some information 
 as to the relative distance from the eye of parts of 
 the surface bounded by the lines composing it, pro- 
 vided we know what the angle is really — that is, 
 know its appearance from a certain position. A 
 rectangular table top, viewed from a point not in a 
 plane passing through the centre of the rectangle and 
 perpendicular to one side, appears a rhomboid, and 
 conversely, to represent a rectangular surface looked 
 at obliquely a painter employs a rhomboidal figure. 
 
 (5) The eyes must turn inward more strongly 
 to look at a near object than at a far object. Like- 
 wise, they must accommodate, that is, change the 
 shape of the lens by muscular action for the near 
 object. The sensations of these muscular adjust- 
 ments give immediate information as to relative 
 distances of objects fixated. Hold up your pencil 
 a foot or so before your eyes and fixate alternately 
 the point and a spot on the wall in line with it; 
 you will find that the convergence and accommoda- 
 tion sensations are quite intense. 
 
 (6) Since the two eyes look at the presented scene 
 from two different points of view, their images do 
 
226 A SYSTEM OF PSYCHOLOGY 
 
 not exactly agree. This disparity of the images of 
 the two eyes is turned to practical account in the 
 stereoscope, which presents two slightly different 
 pictures to the eyes. Since the pictures are origi- 
 nally taken by a camera with two lenses, from two 
 points of view corresponding to those of the eyes, the 
 stereoscope reproduces the binocular disparity of a 
 natural scene. The depth given by a stereoscope 
 view is a demonstration of the importance of the 
 binocular disparity sign in visual perception. 
 
 (7) When you move your head laterally, the view 
 before you changes slightly. An object may be hid- 
 den behind another when the head is in one posi- 
 tion, and emerge when the head moves far enough 
 to one side. An object not hidden by a nearer 
 one apparently moves closer to or farther away 
 from it. The relative amount of parallactic dis- 
 placement indicates the relative distances of the 
 objects. 
 
 Auditory sensations are localized in the space 
 perceived through the visual, tactual, and muscular 
 mechanisms, but not localized accurately. We can 
 usually tell the side from which a sound comes 
 by the difference in intensity for the two ears; and 
 we may make a lucky guess as to its general direc- 
 tion, especially if allowed to turn the head while 
 
PERCEPTION 227 
 
 listening.^ In general, however, we attach the 
 sound to the seen, felt, or imagined object which 
 seems an adequate cause of the sound; hence the 
 success of the ventriloquist. There can be no 
 direct spatial reference of auditory sensation; a state 
 of affairs which is puzzling until we reflect that 
 the actual direction from which the sound ap- 
 proaches can make no difference in the local sign 
 of the sensation. ^ 
 
 6. The Perception of Things 
 
 The reader has doubtless been somewhat sceptical 
 during our exposition of the content of perception. 
 Sensations, relations — these are all very well, and 
 there is no doubt that we do perceive them, but the 
 important features of the world about us do not 
 seem to be exhausted by this simple list. We per- 
 ceive thingSy in which certain qualities inhere, and 
 although one may be persuaded that the qualities 
 are sensations, and that the things stand in percep- 
 tible relations to one another, he can only with 
 diflSculty be convinced of the necessity of abandon- 
 
 ^ Experiments seem to demonstrate that under certain 
 favorable conditions the difference in phase of the sound- 
 waves affecting the two ears (when one ear is nearer the source 
 of sound), may assist in the determination of the direction 
 from which the sound comes. In this case the subject is, of 
 course, unaware of the difference itself. 
 
228 A SYSTEM OF PSYCHOLOGY 
 
 ing the things themselves. Nor would we desire to 
 convince him of such necessity. We have simply 
 labored to show the student of what stuff the things 
 he perceives are made, without attempting to prej- 
 udice his view as to whether this world of things 
 is entirely within himself, as Idealism and Material- 
 ism teach, or whether the conditions are as common- 
 sense assumes them to be. 
 
 The nature of perceived objectivity offers a prob- 
 lem for analysis which is simple as compared with 
 some of the other problems of content. Assuming 
 the perception of space, we find the fundamental 
 feature of thinghood in the location of one sensory 
 quality or group of qualities in the same space with 
 another. It is very probable that an animal re- 
 stricted to one mode of sense would not be able to 
 perceive "things'' as we do. He might perceive 
 spatial relations, but they would be comparable 
 to the spatial relations we perceive in a picture. 
 Allow him, however, the opportunity to identify 
 visual sensations with a definite portion of tactual 
 space, or vice versa, or to identify muscular sensa- 
 tions with parts of either space, and all the essen- 
 tial features of perceived objectivity are present. 
 The "thing'' which we perceive is just the coinci- 
 dence of sensations of diverse modes in definite 
 
PERCEPTION 229 
 
 space relations, and involved in the manifold of 
 other relations component in content. When we 
 become metaphysical, we invent something called 
 "substance'' or "matter'' to act as a mystic cause 
 for this coincidence, but if we did not have the 
 experience of thinghood, substance would never 
 have been invented. The psychological problems 
 involved in the construction of such a concept as 
 that of substance, a concept which in itself is an 
 experienced content, but which represents or refers 
 to the transcending of experience, introduce no 
 new difficulties, but belong to the mountains of 
 details upon which we cannot touch in this outline. 
 
 7. The Perception of Time 
 
 In the field of time perception we find again the 
 division between the apriorists and the aposterior- 
 ists, but no real genetic theory of time has been 
 constructed, nor has any one proposed a plan of 
 time-content reduced to non-temporal factors. As 
 in the case of space, we may assume with proba- 
 bility that we learn, in part at least, to perceive 
 time, but this is hardly more than hypothesis. 
 
 Philosophers of the past were accustomed to 
 ascribe space to "outer perception,'* and time to 
 "inner perception.*^ As these terms are now in- 
 terpreted they meant sense perception and thought 
 
230 A SYSTEM OF PSYCHOLOGY 
 
 (imagination, including memory), respectively, but 
 this interpretation makes the distinction as regards 
 space and time meaningless. We can imagine con- 
 tent which involves spatial relations just as well as 
 we can perceive it, and we can certainly perceive 
 time. It is quite probable that these older phi- 
 losophers had a more subtle meaning than their 
 words adequately express to us; but it is not our 
 task at present to search for this. 
 
 The chief points of temporal content, upon which 
 we shall touch lightly, are (1) passing time and 
 change, (2) temporal extent, and (3) temporal dis- 
 tinction and identification. 
 
 (1) The immediate content, which is called "pass^ 
 ing time, is change in the content of consciousness. 
 We do not mean to say that time is built up out of 
 change, but that change as directly perceived, in 
 abstraction from any critical points in the series of 
 changes, is the passing time. By critical points, 
 we mean conditions of content from which the 
 change is thought to occur, or toward which it is 
 thought to be directed. Thus, if a sensation 
 changes from one quality to another, the two quali- 
 ties are critical points, and in so far as the change is 
 perceived or thought of under the dominance of its 
 relations to these — or their relations to it — it is not 
 mere passing time. 
 
PERCEPTION 231 
 
 Attend, in so far as you can, to the " time stream''; 
 try to watch the "ceaseless avalanche of time'' itself 
 instead of attending rather to the events caught in 
 its rush, as you normally do, and you will find that 
 the content which is thus emphasized is a restless 
 "going, going, going"; a continual motion from 
 nothing in particular to nothing else in particular; 
 just continual change. This change may be in 
 sensation, or in imagery, but as soon as it is defi- 
 nitely located, as soon as the whence and the whither 
 regain their normal emphasis, the passing time 
 merges into concrete change. 
 
 In transforming the world of immediate experi- 
 ence into terms of substance and its attributes, we 
 say that change requires Time in which it may 
 occur; we postulate time as a sort of rack into 
 which events are packed. Such Time, if it exists, 
 is not the object of our direct perception, and al- 
 though we may conceive of it we cannot imagine 
 it. You may image time, but it is always as it is 
 perceived, a concrete succession of changes; or 
 rather it is something which readily becomes such 
 a series under inspection.^ 
 
 ^ Time, with a capital T, is a metaphysical construct quite 
 comparable to Space with a capital S. This is sometimes 
 called ' physical ' time, but would better be designated * logical ' 
 or ' mathematical' time. 
 
232 A SYSTEM OF PSYCHOLOGY 
 
 A succession of changes presupposes seriality, 
 i, e,, intermediacy. The change would be chaos if 
 m2 were not perceived or imaged as between mi 
 and m3. In other words, we intuit in the change a 
 specific relation which we may designate as tem- 
 poral betweenness, or intermediacy. This inter- 
 mediacy, although it is not in the passing time as 
 perceived, is an element in all other time-content. 
 
 Rate of change is measured by the comparison of 
 two series in content. If you notice a certain rate 
 of change in auditory sensation, you are comparing 
 it with the rate of change of such other sensory or 
 imaginative content as is implicitly assumed as a 
 standard. The perception of rate passes so readily 
 into the perception of extent that we must at once 
 consider that factor. 
 
 (2) Temporal extent is the amount of change be- 
 tween determining points. If you note in direct 
 perception how long a sensation lasts, you are not- 
 ing the beginning of the sensation and its end, 
 which are two points of transition in the field of 
 consciousness, between which, if we were restricted 
 to the one sensation, and it were uniform — if it did 
 not vary in any character from beginning to end — 
 there would be no perceived time at all. But we 
 are not restricted to this sensation, and we perceive 
 
PERCEPTION 233 
 
 changes occurring in other sensations — increase or 
 decrease in intensity, and so on — which in their re- 
 lations to the determining points of the first sen- 
 sation constitute the perceived time between those 
 points.^ 
 
 The duration or temporal extent may be made 
 up of the total changes in the content; usually, 
 however, a certain part of the content is selected, 
 and change in other parts is not included in the 
 total. The selected contents are normally the pe- 
 riodic or rhythmic muscular activities: breathing, 
 the heart-beat, or periodic movements of the limbs, 
 as in walking; or even purposely produced pe- 
 riodic contractions of other muscles, as tapping of 
 the finger or slight movement in the throat. 
 
 For practical purposes we find it convenient to 
 use as standard extents of time the cycles of change 
 of certain cosmic phenomena — the periodic pas- 
 sage of the sun across the meridian; the stellar posi- 
 
 ^ The character of sensation which we have called duration, 
 or protensity, is not to be confused with duration in the sense 
 of temporal extent. The sensation would be perceived even 
 if it were not perceived as having temporal extent; and two 
 sensations having different physical durations would be per- 
 ceived as differing in protensity even although no time were 
 perceived as included in either. 
 
 Protensity is the character of sensation by virtue of which 
 it can have perceived duration, independently of any changes 
 it may itself undergo. Duration proper is the protensity 
 filled out by change in other sensation. 
 
234 A SYSTEM OF PSYCHOLOGY 
 
 tions; and so on. Ordinarily, we employ as unit 
 the day, that is, the interval between successive 
 noons. Primitive man subdivided the day by the 
 positions of the sun, corrected, doubtless, by the pe- 
 riodic need and satiety of sleep. A little progress in 
 astronomical observation showed the variation in 
 solar days as compared with the sidereal, and the 
 desire for harmonious subdivisions resulted in the 
 partition of the day on a spatial basis, fifteen de- 
 grees of longitude being the measure of an hour, 
 fifteen minutes of longitude, one minute of time, 
 and so on. These astronomical divisions of time 
 are by no means equal for perception; one minute 
 may be perceived as ten times as long as the next. 
 The symbolical estimation of time is not restricted 
 to the means of astronomical observations, pendu- 
 lums, and such physical devices. Very often we 
 measure intervals by the number of recurrences of 
 physiological phenomena; as heart-beats, breaths, 
 etc.; without regard to the actually perceived time- 
 content. Before this trait was noticed certain 
 phenomena of time-estimation were quite inexpli- 
 cable; the fact that intervals corresponding to some 
 multiple of the respiration-period were more accu- 
 rately estimated than intervals falling between these 
 in length was discovered some decades ago, and, 
 
PERCEPTION 235 
 
 not being referred to the respiration at the time 
 gave rise to much tenuous speculation. In other 
 cases the breathing rhythm seems to be of less in- 
 fluence and the heart-rate to dominate the estima- 
 tions. 
 
 In the direct estimation of time, any variation in 
 the processes by which we estimate, or any change 
 in the attention to them, affects the estimation. 
 The apparent duration of a visual phenomenon 
 occupying three physical seconds will not differ 
 greatly, general conditions being the same, from 
 the apparent duration of an auditory phenomenon 
 of the same physical measure. In neither case is 
 the time-content the change in the auditory or vis- 
 ual content, but in some content— muscular, and 
 perhaps ideational — which is the same in both 
 cases; the beginning and the end of the estimated 
 phenomenon simply mark off a certain amount of 
 this change. The change in the estimated phe- 
 nomenon is perceived simply as change, the rapid- 
 ity thereof being determined by the amount of 
 change in the other series — in the time — to which 
 it corresponds. 
 
 The apparent length of intervals marked off by 
 tactual stimulations varies exceedingly from the 
 apparent length of intervals marked off by visual 
 
236 A SYSTEM OF PSYCHOLOGY 
 
 or auditory stimulation, especially in being more 
 irregular. This peculiarity of tactually limited in- 
 tervals is probably due to the fact that attention to 
 tactual stimulation emphasizes also certain muscu- 
 lar sensations from the member tactually stimulated, 
 and this sensation merges in an irregular way with 
 the more rhythmic muscular sensation constituting 
 the basis of the time-content. 
 
 The passing of time seems sometimes slow, some- 
 times fast. This feature arises from the fact that 
 we are comparing two series of changes whose rel- 
 ative rates are variable. The measure of the time 
 is the series of changes we may call St. The con- 
 tent which is timed by that measure, the mass of 
 sensation from the world about us, itself in constant 
 change, we may call Sc. Now, while the rate of 
 change of St is reasonably uniform — as compared 
 with physical standards — the rate of change of Sc 
 is highly irregular.^ If Sc is changing rapidly, as 
 when a great many interesting events are happen- 
 ing around you, time is perceived as flying. If, on 
 the other hand, Sc goes slowly, as on days of 
 deathly dulness, time is perceived as dragging. If 
 all the changes in content not included in the time 
 
 * Perhaps we should say merely that St is less irregular than 
 Sc. 
 
PERCEPTION 237 
 
 series should become insignificant, the experience 
 would approximate to the perception of eternity; 
 those who have been the subject of this in the de- 
 lirium of fever doubtless remember the horror of it. 
 In retrospect, the time that dragged may seem 
 brief, as compared with an equal physical length of 
 the time that flew. This seeming inversion of the 
 duration relation is due to a peculiarity of our 
 estimation of time intervals whose filling has once 
 passed from consciousness. When you reproduce 
 a series of past events, you time them by the present 
 muscular series, just as if they constituted fresh 
 content; for you could not, if you would, reproduce 
 the past series of sensations forming the time basis. 
 The richer series, now taking longer to run over in 
 memory than does the poorer series, marks off more 
 change in the time series, that is, it seems longer. 
 On the other hand, the events of the past interval 
 may not appear prominently; you may remember 
 that they excited, interested, bored, or otherwise 
 emotionally affected you, and this memory may serve 
 as the symbol of the time length; the tedious ex- 
 perience may be thought of now as tedious because 
 the memory of the content recalls the aflFective or 
 emotional experience connected with the slow pas- 
 sage of the time. 
 
238 A SYSTEM OF PSYCHOLOGY 
 
 (3) The relations of past to present and to future 
 are so invariable and all pervading that they almost 
 defy analysis. Practically all we can do here is 
 to point them out; but that does not signify that 
 the relations are simple. 
 
 The present corresponds to the "here'' of space 
 — the origin in a system of co-ordinates — and past 
 and present correspond to " elsewhere." If we so 
 desire, we can carry the analogy still farther in con- 
 nection with the factors reality and unreality. We 
 may imagine either past or future as real (memory 
 and expectation), or as unreal. I may, for ex- 
 ample, imagine myself as having made a successful 
 balloon ascension yesterday, or as the proprietor 
 of a restaurant to-morrow. We might therefore 
 liken the past and the future to the positive and 
 negative directions of a line, and the fictitious past 
 and future to the ±|/"^. But the analogy breaks 
 down, for the "reality" and "unreality" are not 
 time factors, and we can imagine content as present 
 and unreal, as well as present and real. 
 
 "Reality" may be taken in another way, to sig- 
 nify the intuited as against the imagined. This, 
 again, is not a time factor, since content may be 
 either intuited or imagined as present. It is only 
 in a metaphysical way that I can identify the present 
 
PERCEPTION 239 
 
 with reality, and past and future with unreality; 
 for this identification is not a matter of immediate 
 experience at all, but a symbolic way of stating the 
 time relations. In so far as my immediate experi- 
 ence is concerned, both past and future actually 
 exist.^ 
 
 The temporal factors of pastness and futurity 
 have essentially connected with them the factors of 
 familiarity and novelty. What is apprehended as 
 past is also recognized, that is, it has the element of 
 familiarity; but we cannot say that pastness and 
 familiarity are one and the same thing. Familiar- 
 ity, it is clear, may attach to a content which has 
 novelty; something may be both future and famil- 
 iar. It is quite possible that these factors are ulti- 
 
 ^ There are many interesting problems in the metaphysical 
 view of time. If the past does not exist, any account of it is 
 pure fiction, and history and mythology are alike only at- 
 tempts to systematize a present content, true in so far as they 
 succeed; historical truth depending therefore merely on the 
 extent and quality of our present information. To say that 
 the past does not exist, but did exist is a mere quibble, just as 
 it is to say that to-morrow will he Monday. If the past is, 
 then the events of the past were; if to-morrow is, then the 
 events thereto pertaining will he. To say that to-morrow will 
 be, or that the past was, is either a misstatement or a meta- 
 phor. 
 
 Whatever the " reality '^ factor of content may be, analysis 
 so far has simply indicated it. It is doubtless a relation or 
 group of relations — a ^'feeling of realty," the current empirical 
 philosophy would call it — and there we are obliged to leave 
 it for the present. 
 
240 A SYSTEM OF PSYCHOLOGY 
 
 mate elements, and we may accept them as such 
 provisionally. 
 
 The present moment of perceived time may be 
 said to be a mere position in which all content has 
 its origin, and from which it ceaselessly flows. This 
 present moment, in other words, does not include 
 any duration. In this respect it is like the present 
 moment of logical ('^physicar*) time, which must be 
 represented as a mere point on a line. The actual 
 present, however, cannot be represented by the 
 logical present; that is to say, that when the actual 
 present moment is schematized in such a way as to 
 show the various features of content and of proc- 
 esses connected with it, in logical time relations, 
 this present is represented not by a point, but by an 
 appreciable extent of " physical^' time. 
 
 Another way of describing the relation between 
 the actual present and the logical present is to say 
 that the content may include factors which ap- 
 pear simultaneous, but whose physical causes (and 
 probably whose physiological processes) are sepa- 
 rated by some interval in the physical series. For 
 example: a hand revolving over a dial may pass 
 the zero mark a fraction of a second before or after 
 a bell stroke occurs, and yet the two occurrences 
 may seem simultaneous. The perception of the 
 
PERCEPTION 241 
 
 pointer at a definite place on the dial necessitates 
 an eye movement, which, in some way not entirely 
 understood at present, allows an ^'instantaneous 
 photograph'" on the retina of the pointer at the given 
 place; without this eye-movement the image blurs. 
 When the click appears immediately before or after 
 the eye movement no time is perceived as inter- 
 vening, that is, the visual impression and the audi- 
 tory impression are judged to be simultaneous. 
 
CHAPTER XIV 
 
 AFFECTIVE CONTENT OR FEELING 
 I. Affection and Cognition 
 
 Perception and imagination are classed as cog- 
 nition, and sensation and relations, therefore, as cog- 
 nitive elements. These factors do not exhaust the 
 sum of content, or at least there are sorts of con- 
 tent which have not been demonstrated as reduc- 
 ible to sensation and relation. 
 
 When I experience an object, I may experience 
 it qualified by pleasantness or the opposite. A cer- 
 tain amount of what for want of a better term we 
 may call interest may also attach to the object. If 
 I imagine a content it may be tinged with desire or 
 repugnance. These factors — pleasure, pain, de- 
 sire, repugnance, and interest — constitute the affec- 
 tive tone of the content in so far as they are present. 
 They are sometimes looked upon not as factors in 
 the content, but, (1) as ways of experiencing it, or 
 (2) as attitudes toward it, or (3) modes in which the 
 ego is affected in experiencing it. These three ex- 
 pressions, which are practically equivalent, mean 
 
 242 
 
AFFECTIVE CONTENT OR FEELING 243 
 
 nothing more than that the content of experience 
 is not completely accounted for in analysis in terms 
 of cognitive factors only; that the non-cognitive 
 or affective factors are as truly sui generis as are 
 the cognitive factors. 
 
 Affective content includes not only the elements 
 (or quasi-elements) just mentioned, but also the 
 more complex factors called emotions and emotional 
 tone. For example, the content may be joyful, 
 pathetic, humorous, or revolting. 
 
 Pleasure, pain, interest, desire, and repugnance, 
 may be designated as feelings, or, abstractly, as 
 feeling. Pleasure and pain are designated as 
 hedonic tone or algo-hedonic tone; the experience of 
 pleasure and pain, considered generally, is hedono- 
 algesis.^ Desire and aversion are designated ad- 
 jectively as conative or appetitive, and the experience 
 of them as conation or appetition, 
 
 ^ The term "feeling tone'' is commonly given to pleasure- 
 pain alone: frequently the two qualities are designated as 
 pleasantness and unpleasantness. Some psychologists apply 
 the term "feeling tone" also to certain obviously sensory 
 elements or factors, especially strain and relaxation. 
 
 " Feeling" has been much used in the past in the sense of 
 emotion, but is not so used at present in strict discourse. 
 
 Often, however, the term is extended to cover what we 
 have designated as relational content; thus, a "feeling of 
 similarity" is not an uncommon expression. In loose speak- 
 ing, "feeling" is used to designate any sort of content what- 
 ever. 
 
244 A SYSTEM OF PSYCHOLOGY 
 
 The most conspicuous feature of feeling and 
 emotion is the pairing off of the different qualities 
 and qualitative complexes in antithetical fashion. 
 The two conative qualities are mutually opposed to 
 each other, as are also the algo-hedonic qualities, 
 and for almost every emotion there is an opposite. 
 This raises the suspicion that all the emotions are 
 based on the feelings, and that very probably there 
 are more feelings than the ones we have named. 
 
 2. Pleasure and Pain 
 
 Hedonic tone attaches not only to sensational 
 experiences but also to content of all kinds. An 
 idea is pleasant or unpleasant; the memory of your 
 misfortune yesterday involves painful elements, the 
 idea of the good time to-morrow brings pleasure 
 with it. The recognition of relations, whether in 
 idea or immediate perception, rouses hedonic or 
 algetic factors, and sometimes vividly; even the 
 solution of a problem in Euclid brings pleasure. 
 Emotional states can be classified on the basis of 
 their hedonic tone. 
 
 In some respects hedonic tone resembles sensa- 
 tion. It has the characters of quality, intensity, and 
 duration. Other forms of content (relations, pos- 
 sibly images,) can hardly be said to possess inten- 
 
AFFECTIVE CONTENT OR FEELING 
 
 245 
 
 sity. Affective elements have no specific physical 
 stimuli : in this respect they resemble visceral sensa- 
 tions. But on the other hand, the feelings cannot 
 be identified with any peripheral nervous mechan- 
 ism or process; in which they are analogous to rela- 
 tions. 
 
 The quality and intensity of hedonic tone ac- 
 companying sensations are determined by the sen- 
 
 UNPL 
 
 Fig. 12. 
 
 The curves in fig. 12 represent schematically the relation between 
 feeling and sensation intensity. The abscissa represents the intensity 
 of the sensation, and the plus and minus ordinates represent the corre- 
 sponding degrees of pleasantness and unpleasantness respectively. 
 
 sations in fairly simple ways. The intensity, dura- 
 tion, and the number of repetitions of the sensation 
 seem to be the important factors. If the sensation 
 is of brief duration, it is usually pleasant at low 
 intensities, the degree of pleasure depending on the 
 sensation-quality, and on the individual and his 
 condition. To most of us, a faint smell of lilac is 
 
246 A SYSTEM OF PSYCHOLOGY 
 
 agreeable, but as the intensity of the odor increases 
 the pleasure decreases, changing for some persons 
 to unpleasantness with high intensity of the sensa- 
 tion. (See Curve II of Fig. 12.) For other per- 
 sons the odor may remain pleasant at relatively high 
 intensities. (Curve I.) For the most part, sen- 
 sations are slightly pleasant when suflSciently faint, 
 (Curve III), although some are indeed merely 
 neutral, and some are unpleasant for some persons 
 if above the threshold at all. (Curve IV.) 
 
 The duration of the sensation exercises an influ- 
 ence on hedonic tone; or, rather, the tone varies ac- 
 cording to the duration of the sensation. A flash 
 of color, a brief skin-tickle, a whiff of musk, may 
 be agreeable, although a longer continuation makes 
 the sensation intolerable. In the cases of some sen- 
 sations, the feeling may not be changed to the oppo- 
 site, but simply become less pleasant or more un- 
 pleasant; but the effect of a longer duration of the 
 sensation is always to send the tone in the unpleasant 
 direction. At the same time, it must be remem- 
 bered, the continuance of a stimulation produces 
 progressively less response from the sense-organ, 
 and hence less intensity of sensation. 
 
 Repetition may make a sensation which is orig- 
 inally unpleasant less so, or even pleasant. Bitter 
 
AFFECTIVE CONTENT OR FEELING 247 
 
 becomes a pleasant taste, and discord a pleasant 
 sound, with habituation thereto. Possibly all food 
 flavors are unpleasant to the child experiencing 
 them for the first time; the instinct to eat and the 
 desire to do what others do impel him to continue 
 to ingest the food and drink offered to him, and he 
 quickly learns to like them. Where a sensation be- 
 comes more unpleasant with repetition, the organ 
 has undergone a change — pathological, perhaps — 
 such that the stimulus really produces a more in- 
 tense sensation, as in the case of a tooth which the 
 dentist has been torturing intermittently; or ideal 
 factors have entered, with their effects on feeling, 
 as when one revolts from a formerly toothsome 
 dish after seeing the details of its preparation. 
 
 In the realm of ideas and relations the conditions 
 governing pleasure and pain are highly complicated. 
 That we can remember or imagine affective ele- 
 ments is denied by some psychologists. Perhaps 
 individuals differ in their power of imagining such 
 contents. On the other hand, the idea or image of 
 past or future experience may arouse actual pleasure 
 or pain at the moment of the experience of the 
 idea, and so the belief in reproduced hedonic tone 
 may be due to the mistaking of the tone of the 
 image for the image of the tone. The idea of past 
 
248 A SYSTEM OF PSYCHOLOGY 
 
 events is not always pleasant if the past content was 
 pleasant, nor unpleasant if the past content was 
 unpleasant. The determining causes of hedono- 
 algetic quality seem to lie deep, and to operate in 
 sense perception as well as in ideation; the quasi- 
 principles above laid down in regard to sensation 
 being, perhaps, specific results of these general 
 causes. 
 
 In the first place, the normal physiological activi- 
 ties, those which go on as they should for the wel- 
 fare of the individual and the perpetuation of the 
 species, give pleasure; any interference with the 
 usual course, or anything detrimental to the organ- 
 ism, gives pain.* 
 
 In the second place, whatever simulates some 
 condition which is organically advantageous, gives 
 pleasure. Drugs which produce effects on the ner- 
 vous system temporarily like the effects of rest or 
 
 ^ This connection of algo-hedonic tone with the normal may 
 be supposed to be the result of natural selection. Animals 
 which failed to get pain from mutilation, exhaustion, or hun- 
 ger, and pleasure from food and the society of the opposite 
 sex, would have less chance for individual and racial survival 
 than those which were "normal" in that regard. We should 
 expect to find certain capacities for pleasure, e. g., of intoxica- 
 tion, which are in themselves harmful, that have not been 
 eliminated because of their connection with other and bene- 
 ficial activities, or because natural selection has had no chance 
 at them. 
 
AFFECTIVE CONTENT OR FEELING 249 
 
 normal activity produce also the pleasurable ac- 
 companiments of these conditions. 
 
 In the third place, the carrying out or comple- 
 tion of any activity; the accomplishment of any 
 purpose; or the contemplation of a purpose ac- 
 complished, give pleasure. The hindering or ob- 
 structing of activity; the failure to carry out a pur- 
 pose; the contemplation of a plan obstructed or 
 an accomplishment obliterated; any of these give 
 pain. Solving a problem, carrying out schemes of 
 politics or business, playing a game successfully, 
 contemplating your rise from barefoot boy to 
 banker — these are instances of the one sort. Get- 
 ting "stuck'' in a problem, failing to get command 
 of a game, recalling your recent wealth or influ- 
 ence, are instances of the other. 
 
 The general rule, in short, is that the normal and 
 successful performance of functions, physiological 
 or mental, is accompanied by pleasure, and the 
 fact that certain exceptions occur is evidence merely 
 that the physio-psychological mechanism is not per- 
 fectly adapted for all contingencies. 
 
 As soon as we recognize pleasure and pain as 
 primarily the concomitants of the organic welfare 
 of the individual, we are led to suspect that they 
 are forms of visceral sensation. AVe might reason- 
 
250 A SYSTEM OF PSYCHOLOGY 
 
 ably suppose that the well-being of the vital organs, 
 and the proper discharge of their functions, cause 
 the stimulation of appropriate nerve endings, and 
 as a result, somewhere in brain or in spinal cord, 
 takes place the neural process specifically corre- 
 sponding to pleasure. So too, the vital organs in 
 unfavorable circumstances might arouse sensations 
 of pain. Nervous excitations through the organs 
 of "external" sense, or the neural correlate of idea- 
 tional activity, being intimately connected with the 
 condition of the organism, have possibly acquired 
 either the power to excite the visceral organs by re- 
 flex nervous discharges, or else the power to excite 
 directly the neural centre of hedono-algetic feeling. 
 This sensational theory of pleasure and pain is 
 to be regarded merely as a live hypothesis. It is 
 not at present any more probable than the oppo- 
 site hypothesis; viz,, that pleasure and pain are 
 content of a kind different from sensation. 
 
 3. Conation and Interest 
 
 Desire and repugnance are antithetical, as are 
 
 pleasure and pain, and are usually so connected 
 
 with the lat'ter functionally that what is pleasant is 
 
 desired, and what is unpleasant is repugned/ 
 
 * We use here the verb ''repugn " as the exact opposite of the 
 verb '' desire". This usage is rare in English hterature, but 
 
AFFECTIVE CONTENT OR FEELING 251 
 
 Conative factors attach only to imaged, ideated, 
 and conceived content. If an object is present to 
 sense — intuited — it is pleasing or displeasing, but 
 cannot be desired or repugnant. When an object 
 is perceived, some further content connected with 
 it may be conatively colored. Thus, when fruit is 
 before my gaze, I cannot desire the sight of it, for 
 that I already have; but I may desire the taste, or 
 a continuance of the sight, or the complex relations 
 known as ownership. So the nasty medicine forced 
 on the child is not repugnant as he experiences it, 
 but the taste and effects imagined as a future pos- 
 sibility are decidedly repugnant. 
 
 Interest is verbally the opposite of apathy, but 
 the two factors are not antithetical, as are desire 
 and repugnance. Apathy is really the zero-point 
 of interest, corresponding to the neither-pleasant- 
 nor-painful; the neither-desired-nor-repugnant. 
 There is only one quality of interest. A high de- 
 gree of interest may coincide with either the pleas- 
 ant or the painful, the desired or the repugnant. 
 
 it is necessary to make this addition to psychological termin- 
 ology because we have no other word which can serve as a 
 precise term for the opposite of ''desire/^ *' Aversion'' is fre- 
 quently used for the noun, but is not unambiguous, and has no 
 verb form. We might even venture a step beyond precedent 
 and use the noun "repugn" as the opposite to the noun "de- 
 sire." 
 
252 A SYSTEM OF PSYCHOLOGY 
 
 The glorious sunset; the vile chemical laboratory 
 smell; the recollected images of yesterday's good 
 fortune; the idea of to-morrow's catastrophe; all 
 may be permeated by intense interest. 
 
 Interest attaching to one feature of a complex 
 content spreads over the other factors of the con- 
 tent. The firmer the association between the in- 
 trinsically interesting factor and the other factors, 
 the more these share in its interest. Pedagogues 
 universally recognize this fact, and, therefore, in pre- 
 senting any subject to children, they inject anec- 
 dotes, bring out details which are not essential to 
 the subject-matter, but which are interesting to the 
 child,^ and in every other way possible mingle with 
 the dry material interesting stuff which can be as- 
 
 ^ It is customary to say "appeal to the child's interest/' in- 
 stead of ''possess interest for the child." This form of ex- 
 pression indicates the survival of the view of content of vari- 
 ous sorts as products of the ''faculties" of the individual. 
 Under the "faculty" theory the various terms designating 
 different divisions of the field were applied indiscriminately to 
 the content and to the hypothetical "faculty" producing the 
 content. This " faculty psychology" is by no means dead at 
 present, and has the greatest vitality in the realm of the feel- 
 ings. The student must be careful not to allow the common 
 ways of speaking of psychological facts to draw him into a 
 false understanding of them. You may say "I admire St. 
 Gaudens' statues" and " I became interested in polar explora- 
 tion," but don't forget that admiration and interest, to what- 
 ever activities they may lead, are factors in the content of 
 your consciousness, and not anything supplied by your con- 
 sciousness or your ego. 
 
AFFECTIVE CONTENT OR FEELING 253 
 
 sociated with it. Contemporaneous events; de- 
 tails concerning the person, country, or organiza- 
 tion under consideration, and especially causes 
 and effects, form associative nexus over which the 
 interest readily travels. But even such artificial 
 associations as may be formed between | and the 
 red apples used to illustrate the problem, may 
 carry interest from the fruit to the arithmetic, 
 for the good of the child and the success of the 
 teacher. 
 
 Desire and repugnance spread, but not simply 
 along the lines of association. In certain cases the 
 invariable associates of desired or repugnant things 
 become invested w^ith the given feeling, sometimes 
 to the exclusion of that which it originally attached; 
 but these cases — fetichism, so called — are excep- 
 tional. In general, the organic whole which is 
 ideated — for example, a trip to Europe — is desired 
 (or the reverse) in so far as one or more important 
 factors in the idea have the feeling, but the cona- 
 tive feeling does not tend to flow over and color the 
 other cognitive factors, or at least not to the same 
 extent as does interest. However ardently you 
 desire the European trip, the sea voyage essential 
 thereto may remain repugnant, and certain details 
 of continental travel remain conatively neutral. 
 
254 A SYSTEM OF PSYCHOLOGY 
 
 But your interest in the means and conditions of 
 travel swells almost in proportion to your interest 
 in foreign lands. 
 
 In the particular instance cited, the abhorred 
 factor — the ocean trip — becomes desired, in spite 
 of its unpleasantness, as soon as you begin to make 
 definite plans for beginning your vacation. You 
 contemplate the voyage as a necessary link in the 
 chain of causation which will bring the intrinsic- 
 ally desired details of the stay on the other side. 
 Conative feeling, in other words, spreads along the 
 line of causal relation in the regressive direction. If 
 you desire anything, you will desire the causes 
 thereof, unless those causes are so tinctured with 
 repugnance that the desire of the effects cannot 
 overcome it. There are persons who are such 
 "poor sailors" that not all the joys of the other 
 continents can overcome their aversion to the un- 
 easy ocean. 
 
 Conative feeling never spreads progressively along 
 the line of causation. You may be averse to the 
 sea voyage because of the repugnant consequences; 
 but no matter how much you desire to take ship, 
 the consequent mal de mer will never become in the 
 least desired. However fierce may be your long- 
 ing for any pleasurable content, it will not add one 
 
AFFECTIVE CONTENT OR FEELING 255 
 
 jot to your desire for the consequences, nor sub- 
 tract one tittle from your repugn for them. 
 
 The desire or repugnance attaching to a cause — 
 or what is conceived as a cause — does have an in- 
 fluence on the interest attaching to the effect. If 
 the effect has the opposite conative feeling, it is de- 
 creased in interest, sometimes even to the apathetic 
 point. The dipsomaniac, eager for the pleasant 
 excitement of intoxication, does not desire the next 
 day's wretchedness; but that result he refuses to 
 ideate — it has no interest for him while his desire for 
 intoxication lasts, and interest, as we shall see, 
 is one of the important conditions of attention. In 
 this curious relation of interest to antagonistic cona- 
 tive feeling is doubtless to be found a clew to the 
 further understanding of interest. 
 
 4. Emotion 
 
 Emotion includes in the first place the affective 
 elements just mentioned, and perhaps other such 
 elements. In the second place, it includes among 
 its factors bodily sensation, and in the third place 
 intellectual factors. Sensory imaginative content 
 is included in many instances. 
 
 The affective elements are combined in an organ- 
 ized content in normal consciousness in the manner 
 
256 A SYSTEM OF PSYCHOLOGY 
 
 we have indicated in the preceding section; either 
 hedonic tone, or either conative factor may appear 
 with any degree of interest: if both hedonic tone 
 and conative factors are present, (as in ideation), 
 repugnance goes with pain and desire with pleasure. 
 In morbid imagination the conditions may be re- 
 versed; pleasure may be coupled with repugnance 
 and pain with desire. 
 
 A few examples of affective combination in emo- 
 tion will illustrate the possible exclusions of one or 
 another of the three feeling groups. Grief or joy 
 may be entirely devoid of desire and aversion. 
 Grief may lose interest until it sinks approximately 
 to apathy. Ennui is painful, rather apathetic, and 
 repugnant in so far as its continuance is ideated. 
 On the other hand, the idea of the removal of its 
 cause is pleasant and desired. Hate may be de- 
 void of hedonic tone, and full either of desire or 
 repugnance, according as the object of the hate is 
 thought of as suflFering or prospering. 
 
 Examples of morbid emotion are found in cases of 
 asceticism where the "pleasures of the flesh" are 
 thought of with aversion, and various sorts of pain 
 are desired. The ideal of the monkish life is to rid 
 the ideas of things, commonly desired or repugnant, 
 of their normal pleasure or pain: in so far as this 
 
AFFECTIVE CONTENT OR FEELING 257 
 
 ideal is realized the emotions are not morbid; they 
 are abnormal only in the sense of being unusual. 
 It is possible that in some diseased mental conditions 
 (other than the quasi-ascetic) the patient may desire 
 what is thought of as painful, and be averse to what 
 is thought of as pleasant. 
 
 In cestlietic emotion desire and repugnance are ex- 
 cluded. My present emotion with regard to the 
 Fifth Symphony of Beethoven is not aesthetic; it is 
 a commonplace affair in which the desire to hear the 
 symphony predominates : the emotion while listening 
 to the symphony is sesthetic if no desires are mingled 
 in it. The painting of a mere basket of fruit can 
 hardly arouse aesthetic emotion, because the desire 
 to taste the fruit is excited if the painting is skilfully 
 done (there are exceptions, however), and the repre- 
 sentation of a beautiful woman is decidedly un- 
 sesthetic if it arouses sensuous desire. So, too, in so 
 far as anything arouses repugnance, it is an unaes- 
 thetic object.^ 
 
 The ideals of art are not satisfied by the mere 
 arousal of aesthetic emotion. Art aims to carry us to 
 
 * The ideal religious emotion is complementary to aesthetic 
 emotion, in that desire and repugn are included, and pleasure 
 and pain excluded. The common type of religious emotion, 
 or what passes for such, is generally tinctured heavily with 
 hedono-algetic factors. 
 
258 A SYSTEM OF PSYCHOLOGY 
 
 the point where the sensuous and intellectual con- 
 tent is minimized, and the feeling element is para- 
 mount. This aim can be attained measurably by 
 painting and sculpture, but more adequately by 
 poetry and music. In poetry, the ideas called up 
 by the words are necessarily definite and in so far 
 obtrusive, but the skill of the poet is exerted to 
 subordinate this machinery to the results achieved 
 by its aid. This is the reason why description, 
 narration, or philosophizing, essentially interfere 
 with the poetic effect, although they may produce 
 a pleasing result; and the poet accordingly employs 
 them only in so far as the ideas they arouse are 
 fragmentary and therefore subordinate to their 
 feeling. 
 
 In music, we are less trammelled by the cognitive. 
 The mere sounds are not of high interest in the 
 total complex, and they do not in general arouse 
 definite ideas. There are exceptions, in what is 
 known as "programme-music,'^ in which certain pas- 
 sages are supposed to suggest the singing of birds 
 in the woods, etc., and although some musicians 
 condemn this intrusion of ideas, it may be helpful 
 in some cases. The mingling of music with sensu- 
 ous and intellectual content in opera, while a lower 
 form of art for those able to appreciate pure music, 
 
AFFECTIVE CONTENT OR FEELING 259 
 
 may be a means by which more powerful feeling 
 is roused in certain persons than they would other- 
 wise experience. The purity of the feelings is one 
 ideal, and the strength of feeling and richness of 
 content is another, between which the choice is a 
 matter of personal response. 
 
 5. The Coenaesthetic Factor in Emotion 
 
 The discovery that emotion contains much vague 
 and undiscriminated bodily sensation was made 
 about thirty years ago, simultaneously, by James of 
 Harvard and Lange of Copenhagen. Prior to that 
 time the opinion prevailed that the bodily factors we 
 experience when emotionally moved are conse- 
 quences of the emotion proper— the theory of Des- 
 cartes. Spinoza had stated the doctrine of the 
 bodily factors as an integral part of the emotion, but 
 in a crabbed and symbolic way which produced but 
 slight effect on psychology. Lange and James 
 went so far as to claim that the emotion consists 
 wholly of bodily sensation — the so-called James- 
 Lange theory — and although we are not inclined to 
 grant this claim it is not because we are essentially 
 at variance with the James-Lange view, but because 
 they mean by emotion only what is left over after 
 the intellectual and ideo-cognitive factors are ex- 
 
260 A SYSTEM OF PSYCHOLOGY 
 
 eluded, and possibly after the exclusion of what we 
 have designated as the true affective factors, while 
 we prefer to use the term in the wider sense in 
 which the public understands it/ 
 
 The trembling of the limbs, the modified beat 
 of the heart, the peculiar visceral states, and, per- 
 haps, the results of certain glandular activities, are 
 certainly a large factor in fear, and if they are ab- 
 stracted the characteristic emotion is dispelled. 
 So in the case of pathos; the emotion derives its 
 specific character from certain sensations connected 
 with swallowing and relaxation, characteristic of 
 satisfaction, and with the retching movements 
 characteristic of disapproval or disgust; for the 
 essential thing in pathos is a mingling of these two 
 emotional complexes. Other illustrations of the 
 coensesthetic factor in emotion may readily be found. 
 
 The mass of sensation in emotion is undiscrimi- 
 nated and vague. When you pick out this factor 
 and identify it with the respiration, and identify that 
 factor with the leg muscles, and the other factor with 
 the intestinal condition, the emotion is thereby de- 
 stroyed. It is only so long as these sensations fuse 
 
 ^ For a statement of Professor James's theory, and the multi- 
 tude of facts which suppoix it, read the chapters on '' Instinct 
 and Emotion '' (XXIV and XXV), in vol. II, of his Principles 
 of Psychology. 
 
AFFECTIVE CONTENT OR FEELING 261 
 
 into an undifferentiated mass that they are a ^* color'* 
 or "background" for the cognitive content; when 
 discriminated they are cognitive content themselves, 
 losing their quasi-unique character. Moreover, 
 the visceral sensations are always vague, and 
 identification of them is difficult, even when one 
 makes great effort to analyze. 
 
 It is possible that in many cases the actual sensa- 
 tions are replaced by images thereof; so that a man 
 whose heart and diaphragm no longer respond to 
 the stimulation of a threatening circumstance still 
 may feel fear through the recall of the appropriate 
 sensations in imagination. This supposition would 
 be contrary to the seeming fact that bodily sensations 
 are in general not imagined, but, nevertheless, it is 
 not yet excluded. 
 
 6. The Cognitive Factor in Emotion 
 
 An emotion is always built up on some cognitive 
 content, and loses its distinctive character when con- 
 sidered apart from that factor. The reference of 
 the emotional complex to the "object'' of the emo- 
 tion furnishes the basis of its specific organization. 
 Emotional content not attached to a specific cogni- 
 tive content — which has no^ a specific "object" — 
 is not dignified with the name of an emotion, but 
 
262 A SYSTEM OF PSYCHOLOGY 
 
 is called an emotional mood. Joy and sorrow, di- 
 vested of the definite reference to the object or event 
 which they envelop, become mere elation or depres- 
 sion. Hate which is not the hate of some one or 
 thing is a mere savage mood. These moods are 
 common, and may be produced by strictly physio- 
 logical causes; melancholy, the mood correspond- 
 ing to grief, is notoriously a result of disordered 
 bodily functions. On the other hand, an emotion 
 may resolve itself into a mood which persists long 
 after the transition. 
 
 In addition to the general reference of an emo- 
 tion to its "object,'' there are explicit relationships 
 or groups of relationships involved in emotions. 
 These relations appertain primarily to the "object," 
 but are essential to the emotion. Thus, reverence 
 and contempt involve the perception or conception 
 of the object as superior or inferior in some respect; 
 usually a relation of the sort we designate as per- 
 sonal. Fear involves the consciousness of the ob- 
 ject as threatening us; hope, as possibly attainable. 
 Despair permeates the object which is ideated as 
 forever sundered from our possession. Love has 
 been defined as pleasure plus the idea (or percep- 
 tion) of the object producing the pleasure; this 
 half-truth brings out clearly the fact to which we 
 
AFFECTIVE CONTENT OR FEELING 263 
 
 refer. Mere pleasure, with the perception of the 
 pleasing object, is " taking pleasure in the object," 
 and nothing more; but given the proper relation 
 in which the object is conceived as standing to 
 other things, the emotion may become one of warm 
 approval; and, given certain relations in which the 
 object is conceived to stand to yourself, the emo- 
 tion may become love. 
 
 From the above considerations it ought to be 
 evident that any analysis of the emotions which 
 attempts to reduce them to sensations alone, or to 
 sensations and affective elements, is inadequate. 
 
 7. The Classification of the Emotions 
 
 Many attempts have been made in the past to 
 enumerate the principal or distinctive emotions, or 
 to tabulate the main classes into which all emotions 
 should fall. Success has crowned none of these 
 efforts; they have not even gained ground from 
 which further advance may be made. 
 
 The varieties of emotion are actually indefinite, 
 and practically infinite in number. One emotion 
 shades off into another by slight gradations, and 
 definite delimitation is entirely out of the question. 
 
 We might, indeed, make rough divisions of emo- 
 tions on the basis of hedono-algesis, setting those 
 
264 A SYSTEM OF PSYCHOLOGY 
 
 which contain painful factors over against those 
 which contain pleasant. Or we might classify on 
 the basis of desire and aversion. A distinction has 
 been made also between the egoistic or self-re- 
 garding, and the altruistic emotions. Many other 
 principles of classification might be suggested, but 
 they are for the most part applicable to a few cases 
 only, and they are all practically useless. 
 
CHAPTER XV 
 
 ACTION AND WILL 
 I. Action in General 
 
 The actions of which the human body is ca- 
 pable may be divided usefully into two classes: 
 physiological reflexes and consciousness-reflexes. 
 The first class, which includes the actions in which 
 consciousness plays no essential part, is but in- 
 directly of interest to the psychologist, although of 
 extreme importance in vital function. The physi- 
 ological reflex may be produced artificially by di- 
 rect excitation of the muscles by mechanical, elec- 
 trical, or chemical stimuli; by electrical stimulation 
 of the efferent (motor) nerves; by stimulation of 
 the motor cells of the cortex or in the lower cen- 
 tres; and perhaps by electrical stimulation of cer- 
 tain sensory nerves. The exact method of pro- 
 duction of the natural physiological reflexes — such 
 as breathing, heart-beat and arterial dilation and 
 contraction, intestinal peristalsis, glandular secre- 
 tion, pupillary reflex — need not be discussed in de- 
 tail here. In the case of the pupillary reflex and 
 
 265 
 
266 A SYSTEM OF PSYCHOLOGY 
 
 the heart-beat, the activity of the muscle probably 
 is determined largely by local stimulation. In the 
 case of breathing, the movements are wholly ini- 
 tiated by nerve-currents from centres in the cere- 
 bellum. The movements of swallowing are prob- 
 ably brought about through tactual sensations 
 (from the mouth) which excite certain nerve-centres, 
 which in turn excite the muscles of the mouth and 
 gullet. This last process is usually in part a con- 
 sciousness-reflex. 
 
 Actions of the second class are those in which 
 consciousness plays an important role, and of these 
 four types may be distinguished: sensational re- 
 flexes, or sensory-motor processes; perceptual re- 
 flexes; ideational reflexes, or ideo-motor processes; 
 and voluntary actions, or volitional processes. 
 
 In the sensational reflex the consciousness nec- 
 essarily involved is a sensation merely. Thus, the 
 hand is mechanically retracted upon coming into 
 contact with a hot object; the mere apprehension 
 of heat is sufficient to bring about the reaction, and 
 the apprehension of a definite hot object is not nec- 
 essary, although it may be important for further 
 action. Winking when a cinder gets in the eye, is 
 another typical sensational reflex. It is possible 
 that some of the instinctive actions of the young 
 
ACTION AND WILL 267 
 
 animal may belong to this class. The first suck- 
 ing movement of the babe, for example, may be 
 conditioned by the mere tactual sensations aroused 
 by the nipple on its lips. On the other hand, these 
 actions may be mere physiological reflexes, or they 
 may, for aught we know, depend on definite per- 
 ceptions. 
 
 The perceptual reflex, depending on apprehen- 
 sion of content more complicated than mere sensa- 
 tion, is in adult life more important than the mere 
 sensational reflex. The almost unavoidable wink- 
 ing when some object comes quickly toward the 
 eye; the instinctive putting up of the hand to ward 
 off or catch an object; the flow of saliva at the 
 smell of savory food; the unintentional mimicking 
 of an acrobat by an interested spectator: these are 
 typical perceptual reflexes. 
 
 The consciousness immediately antecedent to an 
 action may not be of presented content at all, but 
 may be purely ideational. Action under such con- 
 ditions we designate as ideational reflex. There 
 are many cases in which the mere thought of an 
 act brings the act about. Think of blinking; of 
 inhaling deeply; of looking behind you; of yawn- 
 ing; and the act will occur. Thinking of the re- 
 sult of the act may be sufficient to produce it; in 
 
268 A SYSTEM OF PSYCHOLOGY 
 
 many cases, thinking of a word is accompanied by 
 the speaking of the word. It is probably true that 
 every act thought of, either by imaging the act or 
 by imaging the result thereof, would immediately 
 " realize itself if there were not other factors which 
 interfere, as there are in most cases. In hypnosis 
 it is probable that these inhibitory factors are sup- 
 pressed, and hence the ideas communicated to the 
 patient have a chance to work themselves out rather 
 freely. If you arouse in the patient's consciousness 
 the idea of a horse, contradictory ideas being in 
 abeyance, he will produce (as nearly as his bodily 
 capacity permits), the acts characteristic of a 
 horse. 
 
 Certain ideas are linked with certain muscular 
 and glandular activities, although they are not the 
 "ideas of" the activities, nor "ideas oV the re- 
 sults. The rather complicated ideational content 
 involved in the notion of shame, for example, 
 causes relaxation of the blood-vessels in such a way 
 as to give rise to a blush. The idea that some one 
 has treated you with indignity causes the changes 
 which are felt in anger. An individual's idea of 
 his superiority to other people may cause him to 
 laugh or to smile. The list of illustrations might 
 be extended indefinitely. 
 
ACTION AND WILL' 269 
 
 If the ideational or perceptual reflex is compli- 
 cated, i, e., if there are a number of details of action 
 which must occur — some simultaneously and some 
 in succession, — in order to produce a definite effect, 
 as in walking or in catching a ball, but if, never- 
 theless, the group of activities is as a whole depend- 
 ent on the ideational or perceptual fact, as in the 
 instances mentioned, the combined actions are 
 called an automatic action. If an automatic action 
 or a complicated physiological reflex occurs with- 
 out its having been learned, it is said to be instinc- 
 tive. If a nestling of a certain age is thrown into the 
 air, it will fly; this first flying of the young bird is 
 an instinctive action. 
 
 Voluntary action is an ideo-motor process, but 
 it includes more than the mere ideational reflex. 
 The specific differentia of the voluntary action is 
 desire (or the opposite). If I merely think of 
 grasping the ink-well which stands on the desk be- 
 fore me, I probably shall not act on the idea. But 
 if I desire to grasp the ink-well, I shall grasp it, 
 unless very influential counter-ideas are in my con- 
 sciousness. 
 
270 A SYSTEM OF PSYCHOLOGY 
 
 2. Volition 
 
 We have indicated above that volition is an emo- 
 tional state which involves as its essential features an 
 idea of a future condition (anticipatory idea) with 
 desire of (or repugnance to) that condition. Not 
 every emotion of desire (or of repugnance) is, how- 
 ever, a volition. A volition is an emotion of desire^ — 
 what we commonly call the "desire of something 
 — in the absence of any influential contrary idea 
 and conation. If you see some choice fruit on a 
 tree and are devising means by which you may 
 obtain possession thereof, it is immaterial whether 
 we say you desire the fruit, or that you will to get it. 
 But if you entertain the idea that the taking of the 
 fruit would be wrong, or suspect that the owner 
 is near; and are averse to the act or its conse- 
 quences under these conditions; and if the aversion 
 is strong enough to prevent the plucking of the de- 
 sired fruit; we should call your content desire, and 
 not volition. 
 
 The total content of consciousness, where it is 
 marked by opposing ideas and conation, is called 
 
 ^ We shall speak only of desire, but with the understanding 
 that the same remarks apply also, mutatis mutandis, to cases 
 in which the conative factor is repugnance. 
 
ACTION AND WILL 271 
 
 deliberation. Put in active terms, you deliberate 
 over (literally, weigh) the desirable and undesirable 
 possibilities in the way of results of the action. One 
 of the ideas may shortly gain the ascendancy; the 
 other either fading out of consciousness or losing 
 its conative strength, and thus the content become 
 a volition. This resolution of opposition or sub- 
 ordination of inhibitory content, by which the mind 
 "pulled several ways" becomes "confirmed in one 
 direction'^ is called decision or consent. Some- 
 times it is called the fiat. 
 
 We are prone to think of deliberation as the hesi- 
 tation of the self between alternative lines of possi- 
 ble activity, and of decision as the active choice 
 by the self of the one or the other. The part played 
 by the self in deliberation and decision may be 
 made more intelligible later, but for the present 
 it is suflScient to say that the most adequate 
 conception of these states is as mere matters of 
 content; there is no discoverable force — as of 
 an Ego or active self — at work transforming the 
 content. 
 
 It is not necessary that deliberation or decision 
 should precede or form a part of volition. The 
 anticipatory idea may be offset by no ideas of op- 
 posing acts or of restraints, and yet the act which 
 
272 A SYSTEM OF PSYCHOLOGY 
 
 succeeds may be strictly voluntary. The boy who 
 sees the apple, anticipates with desire the ingestion 
 thereof, and takes possession of it without a thought 
 of owner^s rights or owner's wrath, performs an 
 action as truly voluntary as if he deliberated over 
 the situation for some time, and came to a decision 
 with an experience of great effort. The line be- 
 tween volition and desire (emotion) is manifestly 
 not sharp, nor is there any great need of making any 
 sharp distinction, either in ethics or in psychology. 
 The distinction between voluntary action and ideo- 
 motor process is clear for the extreme cases, but the 
 two run into each other in a middle ground, where 
 discrimination is impossible. 
 
 The desire of a given effect is called the motive 
 of the desire of its cause, or the motive of the volition 
 based on the latter desire. The boy's desire or will 
 to project the stone through the window may be 
 motived by a desire to annoy the occupants of the 
 house. The term motive is applied also to certain 
 other antecedents of an act; the boy's motive for the 
 window-breaking may be said to be the hatred with 
 which he regards the householder. The motiving 
 emotion has always desire or repugnance as a con- 
 stituent; it is because the boy's hatred for the man 
 includes as its prominent factor a desire to see him 
 
ACTION AND WILL 273 
 
 degraded in some way, that it can be considered a 
 motive. A non-conative emotion cannot motive 
 any desire or volition. 
 
 3. Volition as Activity 
 
 There is one method of describing will, which 
 calls a volition complete only when to the antici- 
 patory idea, the desire, and the predominance of 
 these, there is added the perception of the realiza- 
 tion of the idea. Thus when I thought conatively 
 of picking up the inkstand, and then proceeded to 
 grasp it, I completed the volitional state by the 
 perception of my fingers closing around the glass. 
 A volition regarded from this point of view is more 
 than a mere content or combination of content; 
 it is a process, and cannot be represented by a cross- 
 section of consciousness; it finds its individuality 
 not in any specific sort of content, nor in any specific 
 combination of content at any one time, but in a 
 definite sequence of states of content. This is the 
 doctrine of will as a psychological activity. It 
 differs from the description of volition we have 
 above given merely in the application of terms. 
 All depends on the choice of the specific features 
 of the complicated process which shall be designated 
 by the term volition. 
 
274 A SYSTEM OF PSYCHOLOGY 
 
 According to the system just stated, if the voli- 
 tional process does not issue into fulfilment of the 
 idea, but stops just before the last stage because 
 of some external restraint, it is called determination, 
 or wish. Thus, I determine that I will buy some 
 paper when I next go down town; and I wish to 
 go to the opera to-night. The difference between 
 wish and determination depends on the anticipa- 
 tory idea; if its intellectual factors include possibil- 
 ity, the resultant state is determination; if possi- 
 bility is not included, it is merely wish. The 
 distinction between volition and determination is 
 frequently only a matter of point of view: I try to 
 catch a car, but miss it; from the point of view of 
 catching the car my content was mere determina- 
 tion, but from the point of view of my decision to 
 run for the car, the state was volition. It is not 
 advisable to give much attention to the activity de- 
 finition of will, or to the problems growing out of it. 
 
 4. Automatic Action 
 
 In descending now to automatic action, we mark 
 two stages; first, the elimination of desire, and, sec- 
 ond, the elimination of the anticipatory idea. 
 
 In carrying out a definite series of activities you, 
 in many cases, do not will each one; even when 
 
ACTION AND WILL 275 
 
 each act is separately ideated or undertaken, it is 
 not desired. In an earlier chapter we have spoken 
 of the spreading of the desire from the effect or end 
 to the causes or means; but although this does occur 
 in some cases, it is not essential. Thus, if I desire 
 to get a book from the library across the street, I 
 get up, put on my hat, go across and ring the bell 
 of the elevator in the library, so performing a num- 
 ber of acts which are ideationally initiated, but 
 which individually are comparatively free from any 
 appetitive factor. At the same time, in the course 
 of getting my book I have performed several acts 
 which are not even consciously initiated, although 
 they are like the ones just mentioned, in that they 
 might be initiated ideationally. Walking, for ex- 
 ample, can be done by voluntarily placing the legs 
 and body in the requisite successive positions, but 
 usually it proceeds without either the desire or the 
 idea of these positions. So it is with opening the 
 door, avoiding a car, catching my hat just as the 
 wind lifts it from my head, etc. These are all acts 
 which may be involved in the total action of getting 
 the book, and not only may take place mechanically 
 in the proper order as if they were premeditated 
 severally, but actually are more efficiently performed 
 when they are mechanical. 
 
276 A SYSTEM OF PSYCHOLOGY 
 
 If the movements essential to the carrying out of 
 a series of activities are not perfectly uniform, but 
 require variation to fit the environment (as in walk- 
 ing on uneven surfaces, turning corners, stepping 
 over gutters, etc.) these variations are introduced 
 as perceptual reflexes; you see the gutter, for ex- 
 ample, and the appropriate modification of the 
 action of the muscles occurs without any further 
 conscious intervention. The whole series of walk- 
 ing movements may take place in the same way : my ' 
 idea of getting the book may be succeeded by or 
 include no idea of locomotion; the mere perception 
 of my local situation may start my legs moving. 
 
 An automatic act may be considered as a series 
 of reflexes, perceptual, sensational, or physiological, 
 in which each completed detail serves as a stimulus 
 for the next. Thus, in walking, the shifting of the 
 weight to the left leg may be the stimulus for the 
 extension of the right leg, and so on : these two acts 
 are themselves complex, and the series of muscular 
 contractions which produces them are connected 
 in a reflex way; when one is completed or reaches 
 a certain stage, it sets off the next one. So, the 
 whole process repeats itself automatically and is 
 continued until inhibited by a new idea, perception, 
 or sensation. It is probable that every function- 
 
ACTION AND WILL 277 
 
 ally connected series of acts tends to pass in succes- 
 sion from perceptual to sensational and physiologi- 
 cal reflex-types, as regards the initiation of the 
 particular acts. 
 
 5. Instinctive Action and Learning 
 
 The difference between an instinctive action and 
 an automatic action or complicated reflex whose 
 sequences and combinations are acquired, is simple 
 in theory, although in practice discrimination is not 
 always easy. The action of a young bird's wings 
 in its first flight are instinctive — it never learned 
 these actions. Your actions in waltzing are ac- 
 quired — nature may have endowed you with the 
 capacity for the essential movements of the feet and 
 legs, but you had to learn the right combinations 
 laboriously. The co-ordinating wing-movements 
 of the fledgling may be initiated by the perceptions 
 aroused when the bird first finds itself in the air, 
 or they may be simply complicated physiological 
 reflexes. On the other hand, the conclusion that 
 either of these suppositions is true is at least pre- 
 mature. It is possible that the flying may be initi- 
 ated by ideas or even by the desire of flight. Other 
 instances of complex actions which are instinctive 
 — 2. e., not acquired, — are the feeding of young 
 
278 A SYSTEM OF PSYCHOLOGY 
 
 birds and young mammals, and the first creeping, 
 walking, and talking of young children. Our 
 adult activities are based throughout on instincts, 
 but in the development of these activities the ac- 
 quired part comes to overshadow the instinctive. 
 The turning of door-knobs, buttoning of coats, 
 playing of violins, manipulating of complicated 
 scientific instruments, the use of knives and forks, 
 and so on ad infinitum, are actions initiated by the 
 visual or tactual perception of certain objects; yet 
 the combinations of muscular processes necessary 
 to the accomplishment of these actions have been 
 learned in past experience. 
 
 Learning, in the domain of action, is in every case 
 the combining of simple or relatively simple activi- 
 ties which primarily occur instinctively or acci- 
 dentally, for the accomplishment of something 
 which none of the simple acts could compass. Such 
 learning may proceed in one of three ways: 
 
 (1) The combination may be entirely acciden- 
 tal. The child may by chance make the "th" 
 sound and associate the sound with the proper po- 
 sition of the tongue and lips. The dog confined 
 in the yard noses frantically at the gate until acci- 
 dentally he trips the latch. If the animal is thus 
 fortunate several times he may form an association 
 
ACTION AND WILL 279 
 
 between the percept of the latch and the appropri- 
 ate action. 
 
 (2) Imitation. A child may learn a new pur- 
 posive combination of movements at one stroke by 
 seeing the action performed by somebody else. 
 A peculiar hop or skip, the winding of a clock or 
 mechanical toy; the buttoning of a garment; may 
 be new, but performed fairly well the first time. 
 By far the greater number of actions called imi- 
 tative are, however, combinations of movement 
 processes already learned, applying to specific ob- 
 jects or purposes. Almost all of the imitative 
 bodily postures and gestures fall into this class. 
 Such activities as the putting on of clothes, eating 
 with forks and spoons, and the great mass of 
 practical activities in general, are learned slowly, 
 and can be called imitative only if you wish to 
 apply that term to every non-instinctive action. 
 
 In learning by imitation, strictly so-called, the 
 individual sees an act performed which he recog- 
 nizes as a combination of certain more elementary 
 processes of which he is already master, and then 
 proceeds to perform this group of actions in the 
 specific order and combination, for the first time. 
 An act which is repeated by imitation must be 
 one which the subject has previously performed.. 
 
280 A SYSTEM OF PSYCHOLOGY 
 
 Imitation therefore presupposes a high state of 
 development "mentally" and muscularly. All the 
 components of the imitative act must be under 
 ideational control; must be, in short, capable of be- 
 ing voluntarily performed. If a child can say shoo 
 and gar volitionally or as ideo-motor reflexes, he can 
 succeed tolerably well in imitating your utterance 
 of "sugar/* But if the child has not learned to 
 say the word or the two syllables separately he can- 
 not imitate it. It is possible, however, that if he can 
 voluntarily say " thu,'* he may recognize a similar- 
 ity of that sound to ",su" and make the substitution. 
 
 Imitation has really a small place in the field of 
 learning. In most cases it applies to the already 
 learned. The mere incentive to learn furnished 
 by our observation of what others actually do 
 ought not to be called imitation: the term indicates 
 either a perceptual or ideational reflex, in which the 
 essential percept or idea is of a similar act performed 
 by another person. 
 
 (3) Conceptual analysis. At a higher stage of 
 "mental" development, the individual is able to 
 make new movement-combinations by a process of 
 analysis. A certain situation is presented, which 
 requires a number of movements in combination 
 and succession, e. g,, the operation of a typewriter. 
 
ACTION AND WILL 281 
 
 The beginner may without assistance discover the 
 functions of the keys, the spacer, and the shift, and 
 proceed to combine these functions; to alternate 
 characters and spaces, to hold down the shift while 
 printing a capital, and to hold down the shift and 
 spacer while underlining or accenting. In all this 
 combination there need be neither accident nor imi- 
 tation, although all the movements here combined 
 are put within the individual's power by instinct, 
 and accident, assisted by imitation. Once learned, 
 the combination becomes automatic, if the operator 
 becomes in any wise expert. 
 
 Although for aught we know the lower animals 
 may "learn'' actions altogether without the aid of 
 consciousness, man learns chiefly through volition. 
 But the terminus of the learning process is that con- 
 dition of efficiency in which volition, ideas, and 
 other content of consciousness are eliminated as 
 far as possible from the sequences of the action. 
 
 6. Habit 
 
 One of the most important features in the de- 
 velopment of action is habit. Once a volition has 
 occurred, it is easier for it to occur again. It may 
 occur the first time after "hanging fire" a long time 
 in the "strife" of opposing ideas, but next time the 
 
282 A SYSTEM OF PSYCHOLOGY 
 
 strife is shorter. With each repetition the process 
 is accelerated and made easier, until finally the idea 
 alone will produce the action, and we have the first 
 step toward automatism. If a series of actions 
 occurs habitually in the same order, after suf- 
 ficient time, not only the essential desires and voli- 
 tion, but the ideas as well, will be eliminated and the 
 series once started will unroll mechanically unless 
 modified by new sensations; automatism will be 
 complete. 
 
 Habitual repetition may modify the action in 
 another way. The sensory content which at first 
 aroused the anticipatory idea and desire may become 
 able to do the work alone, by the progressive 
 elimination of the two factors mentioned, thus giv- 
 ing rise to the acquired reflex. The sight of the 
 letter put into your hands may be followed by the 
 opening of the letter, even when you have neither 
 idea nor desire of the act or its consequences. 
 
 The instinctive reflex has been called an inborn 
 habit. Whether the tendency to act in a certain 
 way is, or is not, the result of the habits formed by 
 preceding generations, the instinct is certainly on 
 the exact plan of the habitual action, and can be 
 understood only by beginning with the latter and 
 working down to the former. Yet the order in 
 
ACTION AND WILL 283 
 
 analysis is not necessarily the order in history, and 
 we need assume nothing as to the mechanism and 
 process in the development of the instinct. So far 
 as any one knows, tendencies to think and feel may 
 just as well be inborn as may tendencies to act, and 
 hence we must be cautious in classifying any given 
 act of the young animal as reflex, ideo-motor, or 
 voluntary. 
 
 Habit is an enormous factor in our psycho-physi- 
 cal existence, and has received its due attention 
 from the psychologists. But as yet no explanation 
 has been found for the method of operation of 
 habit. The building up of habit has been likened 
 to the formation of channels by streams of water 
 and to the wearing of paths by successive footsteps 
 which erode the soil deeper and deeper. The laws 
 of habit are sometimes stated in terms of "brain- 
 paths,^' but we must remember that this form of 
 statement is merely a carrying out of the analogy 
 just mentioned, and means little in physiology. 
 All we can do at present is to state the facts psycho- 
 logically, and admitting that they have their physio- 
 logical conditions, keep a sharp lookout for what 
 may be discoverable concerning these conditions. 
 
284 A SYSTEM OF PSYCHOLOGY 
 
 Note 
 
 The "motor tendency of thought" may be ex- 
 hibited in the case of a normal subject by any of the 
 usual means for recording "automatisms." For 
 instance, have the subject's hand resting on a plan- 
 chette, or, better still, on a glass plate resting on 
 three steel balls which roll on a second plate, the 
 upper plate having attached to it a pencil which 
 bears upon a strip of paper. Have a screen so 
 interposed that the subject cannot see his hands nor 
 the pencil and paper. Let him see you trace a line 
 on the wall in front of him, or hear you describe such 
 a line verbally. In nearly every case the subject's 
 hands will move, as shown by the pencil record, in 
 a way corresponding to the line. 
 
 Buckle a strap around the subject's head (over 
 the top of the head and under the chin), and fasten 
 to the strap on top of the head a wooden point. 
 Let the subject stand (with eyes closed) under a 
 sheet of smoked paper supported at one edge and 
 resting on the wooden point. Tell the subject to 
 stand perfectly still, and mention to him interesting 
 objects actually or suppositionally lying in certain 
 directions from him, and he will be found to move 
 in the designated direction, or the opposite, accord- 
 ing to the nature of the object. 
 
CHAPTER XVI 
 
 THE SELF, OR EMPIRICAL EGO 
 
 One of the most obvious distinctions in the con- 
 tent of experience is that between the self and the 
 not-self; between the me and the remainder of the 
 world. Several different distinctions have, how- 
 ever, been described in terms of self and not-self, and 
 the terms are even at the present day used in a 
 variety of significations. Sometimes the terms 
 self and not-self have been applied to an assumed 
 substantial soul, and the world of experience re- 
 spectively; sometimes to ''mind'' and its contents; 
 sometimes to the content of consciousness and an 
 assumed external reality. We are referring here to 
 none of those distinctions. For Psychology, the 
 self and the not-self are both content: with a self 
 and a not-self that are not content we have practi- 
 cally nothing to do, no matter what may be our ar- 
 ticles of faith on the question of the reality of these. 
 
 We have found in the content nothing but sen- 
 sations, relations, and feelings, and possibly images. 
 If this is a complete list of the kinds of content, then 
 
 the self or '*me'' is made up of these factors, or at 
 
 285 
 
286 A SYSTEM OF PSYCHOLOGY 
 
 least can be resolved by analysis into them. We 
 cannot rigidly prove that there is not an objective 
 self sui generis which pervades, accompanies, or is 
 somehow experienced along with the general con- 
 tent. All that we really need to say is, that no one 
 has been able to demonstrate such a factor in con- 
 tent. When you analyze, the self reduces to the 
 forms of content we have described, and no residue 
 can be detected. The self must then be described 
 either as certain factors of content in combination; 
 or as a certain form of combination of content, in 
 simultaneity and succession; or as both. How large 
 a part the form of combination of content plays 
 in the self is a problem too difficult to be taken up 
 here, and is not important for our purposes. Under 
 any plan of description the self is wholly content. 
 The first elements we notice when we attend to 
 the self and attempt to analyze it, are bodily sen- 
 sations. Sensations of warmth, cold, and pressure 
 from the surfaces, with sensations from the joints, 
 muscles, and viscera; combine into a mass which 
 is constantly present, even in the lighter phases of 
 sleep. This mass is a part of the ^^me" in a pro- 
 found sense. On the other hand, certain other sen- 
 sations from the same organs are not fused with 
 this mass, but stand off from it as something for- 
 
THE SELF, OR EMPIRICAL EGO 287 
 
 eign. While we can make no very definite state- 
 ment on this point, it Is probable that anything 
 which gives a sensation a distinctive position, as, for 
 example, relatively high intensity, sharp spatial or 
 temporal limits, or strong associative connection, 
 tends to separate it from the vaguer mass which is 
 at the foundation of the self. 
 
 The feelings are the constituents of the self which 
 are next in importance to the sensations, and they 
 are, apparently, without exception involved in the 
 self. However you may feel — whatever feelings 
 you may "have' ^ — these feelings are a part of you; 
 to name them is to describe in part the sort of self 
 you are — or "have'' — at that specific time. The 
 emotions, which we have concluded are masses of 
 unanalytically apprehended sensations and feelings, 
 are necessarily also factors in the self. This fact 
 was understood by various psychologizing philos- 
 ophers long before the present theory of the emo- 
 tions was elaborated. The emotions, they said, are 
 modifications of the self, and hence of a different 
 order from "perceptions" and "ideas." 
 
 The self, furthermore, contains all the other sen- 
 sations (and relations) which make up the per- 
 ceived human body. The visual and auditory 
 "sensations of the body" are included without re- 
 
288 A SYSTEM OF PSYCHOLOGY 
 
 spect to their distinctness or sharp definition. The 
 body, in short (as an experienced fact, not as a 
 materialized supposition), is fundamentally the self. 
 A striking demonstration of the truth of this state- 
 ment is found in the uniformity with which all 
 naturally developed religions which assume a per- 
 sistence of the self after death ascribe to it a body 
 of some sort. 
 
 Psychic individuality, or self-hood, means thus 
 more than mere capacity for experience. It means 
 the existence of a specific, although complex, con- 
 tent which is persistently present; which, although 
 it changes its total character, changes slowly; and 
 which hence is the standard against which all other 
 content is measured. The self forms accordingly 
 the basis for the perceived continuity of the ever- 
 changing content. Its rhythmic variations with 
 the solar day and the physiological condition serve 
 as the clock of consciousness. When hungry, the 
 idea of the normal steps for obtaining food are 
 brought up through normal association. In the 
 morning, the recurring associations with the morn- 
 ing state of the self bring up the proper ideas for 
 that time of day almost unfailingly. The intricate 
 system of associative nexus which bind past experi- 
 ences together and make our relatively orderly 
 
THE SELF, OR EMPIRICAL EGO 289 
 
 mental life possible might be controlled in some 
 other way, but as a matter of fact they are con- 
 trolled by the particular associations of this bodily 
 self with the other factors in the manifold. 
 
 The self is by no means exhausted by the body 
 and the feelings. Many things to which the body 
 stands in a particularly intimate relation are ab- 
 sorbed into the self. Family, business, and social 
 relations, for example, tend to become relations 
 within the self. 
 
 The mass of habitually experienced content is the 
 self. '^ Thoughts'^ are in some respects more im- 
 portant than percepts. '*As a man thinketh, so is 
 he,^^ is trite but largely true. The phases of per- 
 sonality which are essentially habitual ways of 
 thinking, or habitual sorts of thought content, we 
 usually designate by the term ^* character.'' But 
 the habitual trains of thoughts are, as we know, de- 
 termined to a large extent by the feelings, and not 
 only by mere feelings, but by emotional complexes. 
 So that in the healthy individual, self, including 
 character, is a rather coherent mass of content. 
 
 In many cases an apparently normal individual 
 possesses a double character. The church-going 
 business man, on Sunday, for example, may really 
 think admirable thoughts, which may be allowed 
 
290 A SYSTEM OF PSYCHOLOGY 
 
 to find expression in suitable action. On other 
 days he thinks only of business, and his actions 
 are quite at variance with his Sunday doings. It is 
 quite probable that he builds up a double set of 
 sensational selves, too, one of which is associated 
 with each of the thought-complexes. The evidence 
 for this assumption is found in the fact that his 
 facial and bodily expressions change with his change 
 of character, and give grounds for suspecting more 
 profound organic modifications. Certainly, he has 
 two sets of emotional habits. He really is not a 
 hypocrite, in an ethical sense, but is a diseased per- 
 son, a monster with two selves. 
 
 There are an indefinite number of possible prin- 
 ciples of bifurcation of the self, and these bifurca- 
 tions may be incipient or thorough-going, that is, 
 they may affect only the habits of thought, or may 
 affect the bodily sensations. A man may be pure- 
 minded at certain times, and lewd at others; he 
 may be a buoyant optimist and a downcast pessi- 
 mist; and so on ad infinitum. And any of these 
 divisions of character may by the gradual forma- 
 tion of associations become a cleavage affecting 
 practically the whole personality. There may be 
 three of these fractional personalities, or even more, 
 in a given case. 
 
THE SELF; OR EMPIRICAL EGO 291 
 
 It is probable that none of us are completely free 
 from the taint of divided personality, but most of 
 us need not fear any disastrous developments. The 
 dangerous eases are those in which one side of 
 the character has been long repressed, but is still 
 smouldering. The individual, for instance, gives 
 rein usually to the moral member of his team of 
 selves, and allows the lewd character to express itself 
 only at the infrequent times w^hen he thinks he is 
 safe from the observation of his associates. In this 
 case, some change in the bodily condition, deeply 
 stirring the whole self, gives the repressed self its 
 chance, and flaring up, perhaps suddenly, it be- 
 comes dominant. In extreme cases the sets of 
 ideas constituting the character side of the previously 
 dominant self, and the other groups of ideas asso- 
 ciated with these, are completely lost, and hence the 
 patient not only evinces a seemingly new person- 
 ality, but actually loses the memory of years of his 
 life. These sudden changes are called alterations 
 of "personality y and in the cases where there is re- 
 peated change from one personality to the other 
 or others, the terms alternation of personality and 
 alternating personality are applied. These cases 
 will be further discussed in Chapter XIX. 
 
CHAPTER XVII 
 
 THE DEGREES OF CONSCIOUSNESS 
 I. Consciousness, Attention, and Vividness 
 
 Up to this point we have restricted our discussion 
 as far as possible to the objects of v^hich we are con- 
 scious and the behavior of these objects, that is to 
 say, to the items and processes of content. Now we 
 must undertake the seemingly impossible task of 
 examining consciousness itself. How it is possible 
 to examine consciousness, and in what consists the 
 operation which we thus designate, are problems 
 which are beyond the scope of the present under- 
 taking. As a matter of fact we do study or discuss 
 consciousness, whether directly or indirectly. 
 
 For practical reasons we have somewhat antici- 
 pated the discussion of kinds of consciousness, and 
 have entertained the possibility of distinguishing 
 two kinds; the consciousness of content "present^* 
 (intuition) and the consciousness of content not 
 "present^' (imagination). The fact that neither of 
 these can exist separately, but that what we really 
 find is consciousness of a content partly present and 
 
 partly not present, is no obstacle to the analytical 
 
 292 
 
THE DEGREES OF CONSCIOUSNESS 293 
 
 consideration of the two kinds, and establishes no 
 presumption against the value of such consideration. 
 The case is precisely the same as in the discussion of 
 sensation as such. At the present time, however, 
 there seems to be no practical advantage in the 
 lengthy discussion of these or other hypothetical 
 sorts of experience. 
 
 Consciousness varies in degree. One extreme of 
 the range of variation is commonly known as a high 
 degree of attention, or concentration of attention. 
 The other extreme is inattention, to which the 
 term subconsciousness is also applied. The general 
 designation of attention is thus given only to the 
 higher degrees of consciousness. If referred to the 
 content, the degrees of consciousness are degrees 
 of vividness, which is sometimes called clearness. 
 Thus, to say that I attend to a sensation or percept 
 is equivalent to saying that the sensation or per- 
 cept is vivid. The content not attended to is non- 
 vivid. In a somewhat better use of the term we 
 speak of a high degree of vividness and a low degree 
 of vividness in the two cases mentioned. Whether 
 any content may properly be said to be not vivid 
 at all is a matter which we will consider later. 
 
 The term attention properly signifies a condition 
 or state of consciousness itself. Sometimes it is ap- 
 
294 A SYSTEM OF PSYCHOLOGY 
 
 plied to a certain content as well. When I attend 
 to a sound, I am conscious of an adjustment of 
 head, and possibly of a change in the tension of the 
 muscles of the middle ear. When I attend to a 
 light, I am conscious of an adjustment of the inter- 
 nal and external muscles of the eye. In addition, 
 in both cases, there are sensations of strain from 
 the muscles of other parts of the body; the chest, 
 the face, perhaps, also, the arms and legs. All these 
 factors are sometimes included under the head of 
 attention. Again, the motor adjustments as ap- 
 prehended by another individual are referred to by 
 the name attention. A dog, for example, is said to 
 ^* attend'' to an object when his sense-organs are so 
 adjusted as to give him the best condition for stimu- 
 lation by the object, although we make no assump- 
 tions as to the dog's consciousness. The student 
 may later find it difficult to escape falling into con- 
 fusion on account of the varying uses of the term 
 by different authors. 
 
 The total content of consciousness at any given 
 moment is conventionally spoken of as the "field 
 of attention" or "field of consciousness." It is 
 likened to the visual field, i, e,, to the mass of visual 
 content "spread out" before the eye at any given 
 time. This analogical treatment is quite defensi- 
 
THE DEGREES OF CONSCIOUSNESS 295 
 
 ble, since we may consider visual content as typical 
 of all content. In this field of consciousness, as 
 spatially analogized, we may represent the highest 
 degrees of vividness at the centre, and the lesser de- 
 grees by zones at different distances therefrom. 
 The centre of this conventionalized field is called 
 the " focus," and the most remote portions are called 
 the "fringe" of consciousness. 
 
 A question which naturally arises at this point is 
 as to the number of discernible degrees of atten- 
 tion. Are there three degrees: a focus, a fringe, 
 and an intermediate region ? Or are there only two 
 grades, focal and non-focal ? or are there four, five, 
 or more grades ? This question may be left open 
 for the present, as no adequate means of determining 
 the number of degrees has yet been found. 
 
 2. Vividness and Intensity 
 
 Vividness is sometimes confused with intensity. 
 Hence it is necessary to distinguish carefully be- 
 tween the two, as well as to consider their connec- 
 tions. Suppose you are talking to a friend, while 
 a large clock is ticking loudly on the mantel. The 
 clock, we will suppose, is in your range of vision, 
 and the ticking is plainly audible, but neither is of 
 much consequence in your total content until your 
 
296 A SYSTEM OF PSYCHOLOGY 
 
 friend remarks "what a curious old clock! '^ Im- 
 mediately the clock (visual and auditory) becomes 
 vivid, and the features and voice of the person be- 
 come reduced in vividness. Has the intensity 
 (loudness) of the ticking, or the brightness of the 
 visual sensations increased? Not to any appreci- 
 able extent; neither has the loudness of the speaker's 
 voice decreased, nor the intensity of the visual pres- 
 entation of his features waned. The "focus of 
 consciousness '^ has shifted, or rather, the impres- 
 sions have shifted as regards the focus, but changes 
 in intensity, if they occur, are purely accidental, and 
 are due to such factors as change in position of the 
 eyes, or in the tension of the ear-muscles. (We are 
 not considering, of course, the possible actual changes 
 in the physical intensity of the voice, or in the il- 
 lumination of the room.) 
 
 Attempts have been made to determine the ef- 
 fects of vividness on intensity of sensation, with re- 
 sults which are seemingly contradictory, but really 
 harmonious. The characteristic method of exper- 
 iment is to find what intensity of a sensation of given 
 quality will be judged equal to the intensity of a 
 sensation of the same quality which immediately 
 precedes or follows it, when the subject "gives full 
 attention '^ to one of the pair, and is "distracted'* 
 
THE DEGREES OF CONSCIOUSNESS 297 
 
 somewhat from the other by accompanying sensa- 
 tions, or by performing mental labor, as adding or 
 multiplying, or repeating verses. The other con- 
 ditions are kept as constant as possible for both sen- 
 sations. 
 
 Some experiments have apparently shown that a 
 sensation to which full attention is given, is judged 
 equal to a sensation which is less vivid, when the 
 intensity of the more vivid sensation is slightly less 
 than that of the less vivid one. Other experiments 
 have shown, on the other hand, exactly the reverse. 
 Hence we have had some experimenters claiming 
 that attention to a sensation increased the intensity 
 while others have claimed that the attention de- 
 creased the intensity. 
 
 As a matter of fact, these experiments have no 
 bearing at all on the question of the relation of in- 
 tensity and vividness. They simply bear on the 
 judgment of relative intensity, which is a different 
 matter. Similar results may be obtained in the case 
 of judgment of size, as when two squares are com- 
 pared; and in the case of judgments of quality. 
 
 That intensity affects vividness we cannot deny. 
 A rapid change in the intensity of any sensation — 
 either increase or decrease — tends to bring it to the 
 focus of attention. Of several sensations or sen- 
 
298 A SYSTEM OF PSYCHOLOGY 
 
 sation-complexes, the most intense will probably 
 have strongest claim on the attention, other things 
 being equal. Other factors are, however, so much 
 more important that little effect is produced by the 
 mere intensity. 
 
 3. Factors Determining Vividness 
 
 A. Sensational Factors. — Intensity, we have just 
 considered. Ex tensity and area may operate in 
 the same way. The larger tends to obscure the 
 smaller. Of two pictures hung on the wall, equally 
 lighted, and not essentially different in coloring, 
 character of subject, etc., the larger will get the at- 
 tention first. Of two touches, two tones, two pains, 
 similar statements may be made. Quality may 
 have some influence. Red, for instance, may at- 
 tract the attention more than blue. Visual sensa- 
 tions usually take precedence over auditory, and 
 olfactory over both. All of these sensational factors 
 are of slight importance as compared with the others 
 mentioned below, and their effects may be due to the 
 feeling factors which accompany them. 
 
 B, Affective Factors. — In the case of feelings, 
 intensity is more important than in the case of sen- 
 sations. The more intense feelings always have 
 a great advantage in vividness. Perceptions and 
 
THE DEGREES OF CONSCIOUSNESS 299 
 
 ideas attended by intense feeling are therefore usu- 
 ally found to be occupying the focus to the exclu- 
 sion of complexes with weaker feeling-componentis, 
 in accordance with the association factors mentioned 
 below. Whether one sort of feeling is more ef- 
 fective than another in this way, we have no grounds 
 for affirming or denying, since it is not possible to 
 equate intensities of two sorts of feeling. We can 
 decide that the pleasant feeling of one complex is 
 approximately the same in intensity as the pleasant 
 feeling of another, or at least not appreciably dif- 
 ferent, but comparison of pleasant feeling with un- 
 pleasant feeling in degree of intensity is definite only 
 when one is noticed to be relatively much greater 
 than the other. 
 
 C, Association Factors, — The whole matter of 
 the rise of ideas through association is one of vivid- 
 ness. One percept or idea occupying the focus of 
 consciousness tends to bring in its associates. If 
 the primarily focal content forms with its associates 
 what we call a single object, the associates are sim- 
 ply added to the focal content. If the associates, 
 on the other hand, form objects distinct from the 
 primary content, the latter drops out as one of the 
 former comes in. The feelings associated with a 
 certain percept or idea come under the first rule, 
 
300 A SYSTEM OF PSYCHOLOGY 
 
 hence the tendency above noted, for the content 
 having the more intense feeling associated with it to 
 gain the ascendency over the content with less in- 
 tense feeling associates. The statement that two 
 distinct objects are attended to successively applies 
 only to the case where one of them occupies the 
 focus before the other is called up through associa- 
 tion. That two different objects may occupy the 
 focus simultaneously under certain circumstances 
 is perhaps true, but is to be considered later. It 
 must be noted, however, that when several distin- 
 guishable objects form a functionally connected 
 group, as a hunter and his prey, a church and the 
 congregation, they may constitute at a given time a 
 single co-ordinated content, although from other 
 points of view they may constitute distinct, even 
 conflicting, contents. 
 
 D, Relational Factors, — Relations determine viv- 
 idness of related content, inasmuch as they form 
 nexus among the factors of content. Nothing need 
 here be added to the discussion of the function of 
 relations in association. On the other hand, re- 
 lations seem to have a distinct advantage in vivid- 
 ness over sensorial content. In a focal content the 
 relations are usually the most vivid part. This is 
 especially true of " thought. '* Our thinking con- 
 
THE DEGREES OF CONSCIOUSNESS 301 
 
 stantly tends to be conceptual, rather than of the 
 sensory-imaginative type. In actual perception the 
 situation is often reversed, and the sensational fac- 
 tors are focal at the expense of the relational. 
 
 E, Other Factors, — Anything singled out, or spe- 
 cifically characterized objectively, is thus made lia- 
 ble to especial vividness. The first and last letters 
 of a written word, a note or word marked by a pre- 
 ceding or succeeding pause, a trilled or syncopated 
 note, a bit of color in the scenery unlike the sur- 
 rounding hues, an element having a humorous sig- 
 nificance or any other emotional coloring widely 
 different from that of other elements — these receive 
 especial attention. The list is indefinitely long. 
 
 4. Attention and Interest 
 
 Interest is sometimes named among the condi- 
 tions of attention. That the feeling we have earlier 
 referred to by the name of interest does predispose 
 to vividness the content associated with it, is indis- 
 putable. The same is true of any emotion or emo- 
 tional factor. 
 
 When, as is sometimes the case, attention is 
 treated as exclusively a matter of interest, the term 
 interest is not used to designate an affective con- 
 tent, but an abstract potentiality. Interest ascribed 
 
302 A SYSTEM OF PSYCHOLOGY 
 
 to any possible object means in this case the fact 
 that when that content arises it will probably be 
 vivid (^. e,, attended to), and that the probability 
 of the rise of that content is relatively high. Inter- 
 est is in this sense by no means a cause of attention, 
 but a mere abstraction from the observed or proba- 
 ble course of attention-changes. 
 
 It is so easy to shade from one meaning of the 
 term interest to another, that the student must be 
 on the alert when following any exposition of the 
 psychology of attention in which the term is given 
 an important place, lest he be led to accept as 
 analysis what is merely a confusion of thought. 
 
 5. Vividness and Practical Advantage 
 
 The greater efficiency of conceptual thought as 
 compared with thought which depends more largely 
 on the sensory image can hardly be disputed. By 
 efficiency we mean here the celerity and accuracy 
 with which a conscious result is obtained, as in 
 solving a problem, or making a decision. Hence, 
 the tendency to greater vividness of relations as com- 
 pared with "imaged^' sensations can be regarded 
 as having arisen or having been conserved because 
 practically advantageous. The same interpreta- 
 tion can be brought to bear on every general con- 
 
THE DEGREES OF CONSCIOUSNESS 303 
 
 dition of vividness. The objects which are most 
 intense and most strongly charged with feeling are 
 the ones to which it is, in general, mentally advan- 
 tageous to attend. 
 
 6. Judgment 
 
 The distinction between concept and judgment 
 is entirely a matter of relative vividness among the 
 factors of these complexes. If I have the concept 
 of a horse, with a definite relation of horse to hay 
 especially vivid, I have (psychologically) a judg- 
 ment which I express (logically) by saying that the 
 horse eats hay. 
 
 In general, a judgment involves two concepts; 
 but again, in general, no concept stands alone. I 
 cannot conceive a horse without several other sub- 
 sidiary concepts entering into the content, and, in 
 the judgment, one of the subsidiary concepts, with 
 a definite system of relations linking it to the central 
 concept, simply becomes more vivid. 
 
 From the preceding it ought to be plain that the 
 function of the judgment is the growth of the con- 
 cept. If the relation emphasized by the judgment 
 is already a part of the concept, the judgment is 
 analytic. For me to form the judgment which I 
 express logically by the proposition, "Water lays 
 
304 A SYSTEM OF PSYCHOLOGY 
 
 dust/' adds nothing of value to my mental content 
 or functions. My concept of water already in- 
 cludes the relations to desiccated substances, which 
 I call wetness. But when I first discovered that 
 water can be produced by the union of two gases, 
 the judgment constituted by my apprehension of 
 that (to me) new relation of water was synthetic. It 
 permanently modified the concept. Included in 
 my concept of water from that time forth was that 
 relational complex which I express when I say, 
 " Water is composed of oxygen and hydrogen." 
 
 7. The Scope of Attention 
 
 How many things — how many functionally dis- 
 tinct factors in content — may be attended to at 
 once? In general, only one, as you may verify 
 introspectively by the aid of a little experimenta- 
 tion. Arrange several articles on a table in front of 
 you, and if a clock is ticking, or a gas flame audi- 
 bly roaring in the room, and if the finger is pressed 
 firmly on some hard object — e. g., the edge of a 
 paper-cutter — you will have a sufficient range of 
 objects. Attend to one of the content factors, and 
 the others coincidently recede from the focus of 
 consciousness. Seldom, if ever, can you succeed 
 in retaining two of the objects at high vividness. 
 
THE DEGREES OF CONSCIOUSNESS 305 
 
 When an object — an ink-bottle, for instance — 
 IS low in vividness it may be rather uniformly vivid. 
 But when the focus of attention shifts to the object 
 it is apt to fall upon some limited feature. Thus, 
 when attending to the ink-bottle, you will find that 
 it is the top, or the bottom, or the cork, or the label, 
 or the ink, or some such detail which is focal. The 
 other portions of the bottle are less vivid. We may 
 say in general that the content occupying the focus 
 of attention is relatively simple. But, in a content 
 which does at one time occupy the focus, we may 
 later (in memory) discover many details. These 
 details, in the later analysis, occupy the focus suc- 
 cessively. 
 
 Several relations can be focal simultaneously only 
 in so far as they join in a single concept. Two dis- 
 tinct concepts are probably never present at once, 
 even in the formation of a judgment. 
 
CHAPTER XVIII 
 
 THE TIME RELATIONS OF CONSCIOUSNESS 
 I. Presentation and Image 
 
 In earlier chapters we have concluded that what 
 is commonly known as the image is not different in 
 kind from sensation, but that the difference is in the 
 way of being conscious. The difference, in short, 
 is in the time factor. If we are now conscious of 
 what is now here, the content is called sensation; 
 if we are now conscious of what was formerly here, 
 the content is called image. The time factor needs 
 somewhat further elaboration. 
 
 There are two distinct temporal phases of a pres- 
 entation, which may be provisionally distinguished 
 by reference to the assumed cortical process. The 
 presentation does not cease when the cerebral proc- 
 ess ceases. We may call the phase of sensation in 
 which the cortical process is active the primary 
 phase, and the phase after the practical cessation 
 of the cortical process the secondary phase. This 
 secondary phase of the presentation is distinct from 
 
 the image. 
 
 306 
 
THE TIME RELATIONS OF CONSCIOUSNESS 307 
 
 If we observe a regular series of brief visual or 
 auditory sensations — clicks of a telegraph sounder, 
 or flashes of light — we find that they may be so ar- 
 ranged that the successive sensations do not fuse; 
 each is separate and distinct from the preceding 
 and succeeding ones; but several may be simul- 
 taneously present to consciousness. If four suc- 
 cessive sounds, for example, are given in one sec- 
 ond, they may be apprehended simultaneously, 
 although not as simultaneous. You may easily 
 demonstrate this, employing taps of your finger or 
 pencil on the table. When the fourth tap is in its 
 primary phase, the preceding three must be in their 
 secondary phases. If they were yet in the primary 
 phase, the four would fuse into one continuous 
 sound. Compare the four just when the fourth 
 arises with the same four a few moments later (as 
 memory images), and you note the difference at 
 once. As apprehended simultaneously, they are 
 sensations and not images. 
 
 This peculiarity of sensations is of great impor- 
 tance in practical life — as, for example, in " taking'^ 
 telegraphic messages, where the operator is con- 
 scious of a sequence of dots and dashes as a whole, 
 instead of having to carry the first part of a letter 
 in memory until the last arrives. In spoken and 
 
308 A SYSTEM OF PSYCHOLOGY 
 
 written language, too, this power of consciousness 
 is of enormous importance. If you were listening 
 to the preceding sentence you would not have to 
 understand " enormous ^^ and carry it over in 
 memory to modify "importance"; you would 
 grasp the two literally together with a vast saving of 
 mental process. In addition to the practical con- 
 sequences of the secondary phase of sensation we 
 find an important aesthetic factor in rhythm, which 
 is made possible by it, and to the discussion of 
 which we shall proceed in a moment. 
 
 This apprehension, simultaneously, of factors 
 which are apprehended as non-simultaneous, is 
 described by the term, "the specious present.'^ 
 The present moment, referred to content alone, 
 stands as a mere inextended point dividing the 
 past from the future. Since mathematics and logic 
 must regard time altogether from the point of view 
 of content, we have come to regard this as the real 
 present. Hence, the term "specious present'^ 
 (apparent or seeming present) applied to the pres- 
 ent of consciousness.^ But this "specious" pres- 
 
 ^ This explanation of the term '^specious" as applied to the 
 present is in strict accordance with the intention of Mr. E. R. 
 Clay, who first used the term. Cf. James, Principles of Psy- 
 chology, vol. I, pp. 606 ff. Other explanations (as that of the 
 Century Dictionary) are obviously erroneous. 
 
THE TIME RELATIONS OF CONSCIOUSNESS 309 
 
 ent is just as "real'' as the other, and there is ab- 
 solutely no confusion between the two presents. 
 Because I apprehend the successive terms A, B, C, 
 D simultaneously, I do not necessarily apprehend 
 them as simultaneous. 
 
 2. Rhythm 
 
 A fairly regular sequence of stimulations — clicks, 
 taps on the skin, flashes of light, etc. — does not 
 usually give rise to a uniformly progressing series 
 of sensations. The greater part of our sensations 
 belong in definite groups, as in the case of words of 
 language, and the grouping habit is so thoroughly 
 ingrained in us that we group objects which have no 
 intrinsic demands for such treatment. 
 
 Suppose we allow water to drip slowly from a 
 small tank onto a tin plate, producing thus a dis- 
 tinct noise for each drop. Let the rate of flow — 
 ^. e,, the rapidity of the succession of drops, be con- 
 trollable. Suppose at first we choose a rate of 
 between two and four drops a second. In listening 
 to the perfectly uniform series of sounds thus pro- 
 duced, you will find that very seldom does it pro- 
 ceed monotonously. In most cases the sounds are 
 automatically grouped in twos, threes, fours, or sixes. 
 The exact numerical size of the group will depend 
 
310 A SYSTEM OF PSYCHOLOGY 
 
 on the rate, the intensity, the Hstener, and on sug- 
 gestions he may get from other processes he is ex- 
 periencing or has experienced; as the ^*clickety- 
 click" of the street-car which passed the building 
 a moment or two before. 
 
 The listener can easily give himself suggestions 
 as to the grouping. If he thinks of hearing a 
 "three-group'' the drops will usually organize 
 themselves in that form. The chief limitation is 
 that the groups will in general not extend over two 
 or three seconds, although occasionally larger 
 groups are formed. This temporal limit seems to 
 be the span of consciousness, or the limit of the 
 "specious present." Another limitation is in the 
 number of the sensations; too many in a specious 
 present give rise to confusion and abolish regular 
 grouping. 
 
 If the terms of the series are absolutely uniform 
 in the case of the water-drops, and if the degree of 
 attention is fairly constant, the grouping depends 
 altogether on the time relations of secondary phases 
 of the sensations. \Mien the final term of a group 
 arises the foregoing terms of that group are still 
 present; with the arrival of the first term of the 
 next group the group just completed disappear from 
 consciousness as presentations — the slate is washed. 
 
THE TIME RELATIONS OF CONSCIOUSNESS 311 
 
 as it were. This sort of a rhythm is apparently due 
 to the periodic contraction of the specious present, 
 occurring at the beginning of each group. 
 
 In many cases attention is not uniform. The 
 drops may be heard in groups of four, for example, 
 and the vividness of the first drop may be higher 
 than that of the succeeding three. This is "sub- 
 jective accent ^^ properly so called. 
 
 The rhythm is much more distinctly and readily 
 developed if "objective accent'^ is permitted. If, 
 for example, by holding the finger on the tin plate 
 on which the drop falls during the time of three 
 drops, and lifting it for the fourth, the intensity 
 of the fourth drop is made relatively higher than 
 that of the others, the drops will tend to fall into 
 groups of fours, the accented drop usually being 
 the first of each four. Various devices are em- 
 ployed for producing series of auditory, visual, and 
 tactual sensations, and if these devices are so ma- 
 nipulated that periodic variations in intensity, ex- 
 tensity, duration, quality, or local sign are intro- 
 duced, these variations serve as accents to determine 
 the grouping. Periodic variations of the time rela- 
 tion of the stimuli may also produce the same effect. 
 
 With objective accent the periodic shrinking of 
 the specious present takes place just as when there 
 
312 A SYSTEM OF PSYCHOLOGY 
 
 is no objective accent; and the groups are usu- 
 ally eliminated as wholes. If the groups are very 
 short two or even three groups may be elimi- 
 nated simultaneously, the contraction of the spe- 
 cious present taking place with every second or 
 third group. 
 
 An important source of objective accent is found 
 in muscular sensation. Very often, when there 
 seems to be a purely subjective accent, it will be 
 found that the stimulations are accompanied by 
 slight muscular contractions in finger, arm^ throat, 
 chest, or elsewhere, and these are accented by varia- 
 tions in intensity, so that the grouping of the ex- 
 ternally presented sensation is really directed by the 
 accenting of the muscular sensations. It is pos- 
 sible that pure subjective grouping is a very rare 
 occurrence. 
 
 Rhythm is important in music and in poetry, 
 especially in the former; the span of consciousness 
 demanded by the rhythmic groups has a large share 
 in the determining of the emotional character of 
 the composition. A short musical unit tends to 
 light, vivacious, or joyful effects, irrespective of the 
 rapidity of succession of notes, or of the melodic 
 intervals employed. A unit which "draws out'^ 
 the specious present slightly beyond the normal 
 
THE TIME RELATIONS OF CONSCIOUSNESS 313 
 
 length produces a sombre effect. A still longer unit, 
 which is divided between two not long spans of 
 consciousness, gives an effect which is solemn, but 
 not sad. Specific effects are produced by units of 
 such length that two occupy a long span or a short 
 span. All these effects are modified — sometimes 
 counteracted — by the other musical factors intro- 
 duced by the composer. In music of the so-called 
 " intellectuar' sort there is no regular relation be- 
 tween the musical unit and the span of conscious- 
 ness; the unity here is intentionally ideational 
 and does not appeal to the average hearer, who is 
 baffled in his natural attempts to fit musical unit to 
 specious present, and only by repeated experience 
 acquires the other method of appreciation. 
 
 3. Duration of Attention to Continuously Presented 
 
 Sensation 
 
 The rhythmic variation of the span of conscious- 
 ness which we have just discussed has to do only 
 with sensations of an intermittent nature. We must 
 now consider cases where the stimulus is continu- 
 ous and, hence, the sensation is continuously pre- 
 sented. Such a case is afforded by the note of a 
 steadily vibrating tuning-fork, or the noise of a small 
 stream of water. 
 
314 A SYSTEM OF PSYCHOLOGY 
 
 In most cases these continuous noises, if rather 
 loud, persist in the focus of consciousness for some 
 time; perhaps for minutes, perhaps for hours. 
 After awhile, however, the sound may become mar- 
 ginal. The duration of a continuously presented 
 sensation or sensational complex in focal conscious- 
 ness depends on the rise of other sensations or 
 ideas which may take its place. If you sit beside 
 a water-fall with your mind at rest, the purl of the 
 water may continue vivid for hours, or if temporar- 
 ily obscured by the other presentations of nature or 
 by fleeting ideas, returns quickly to its place. But, 
 if you have a problem to solve, a book to read, a 
 friend to talk with, or a hill-side to watch for game, 
 the water-fall quickly becomes an inconspicuous fac- 
 tor in the total field of consciousness. So it is with 
 all other presentations. The intense stimulus may 
 force the sensation into the focus for awhile, but 
 finally the mere intensity becomes ineffective. 
 
 The effect of habituation in eliminating the per- 
 sistent sensation from attentive consciousness may 
 be illustrated in a great many ways. The noise 
 of the street which annoys the countryman stay- 
 ing at your house is practically unnoticed by you; 
 yet the ear does not lose its sensitiveness to the noise 
 as does the nose to a continuing odor. During the 
 
THE TIME RELATIONS OF CONSCIOUSNESS 315. 
 
 greater part of the day you hardly notice the sensa- 
 tions aroused by the rubbing of your clothing on 
 your skin; to a savage first clothed the sensations 
 are intolerable. The lights of the lamps and win- 
 dows on the street at night you scarcely notice at 
 all; your rural friend is so attentive to them that he 
 can hardly converse with you. We find, in general, 
 in addition to the physiological adaptation which 
 protects us from continued stimulation, a sort of 
 protective adaptation of consciousness itself by 
 which the persistent sensations not eliminated by 
 physiological adaptation are relegated to the mar- 
 ginal consciousness, unless they exercise solicitations 
 other than those of mere intensity. 
 
 The relegation of intense sensations to marginal 
 consciousness through habituation is realized also 
 in case of sensations not continuous, but which 
 are repeated at frequent intervals. The train rush- 
 ing by every half-hour; the clock striking every 
 hour; even a church-bell ringing at morning, noon, 
 and night; soon becomes without power to disturb 
 the focus. If the interval between stimulations is 
 long this habituation does not occur. Thus, a 
 church-bell ringing only on Sunday mornings may 
 be as vivid at the end of a year's disturbance thereby 
 as at the beginning. 
 
316 A SYSTEM OF PSYCHOLOGY 
 
 4. The Fluctuations of Minimal Sensations 
 Sensations of uniform minimal intensity show a 
 peculiar intermittence in presentation, to which is 
 commonly applied the confusing name "fluctua- 
 tions of attention/^ If one attempts to listen to a 
 sound, for instance, which is physically constant 
 and just above the threshold, he finds that the sound 
 is clearly discernible for short periods and in inter- 
 vening periods is not to be heard at all. The times 
 of absence and presence may vary from a fraction 
 of a second to over ten seconds. Faint sensations 
 of certain other modes behave in the same way. A 
 small gray spot on a background slightly darker, 
 for example, will appear and disappear periodically 
 under the best obtainable conditions of attention and 
 accommodation. 
 
 It has been supposed that these fluctuations are 
 due to varying states of muscular adjustment in the 
 end-organs, and, in fact, slight changes in accom- 
 modation have been found to accompany the visual 
 fluctuations. This theory is excluded by experi- 
 ments which absolutely preclude any adjustmental 
 variation and which yet find fluctuations occurring. 
 The theory which is most probable assumes the 
 physiological cause to be a periodic variation in the 
 
THE TIME RELATIONS OF CONSCIOUSNESS 317 
 
 functioning of the nervous mechanism; either of 
 the nerve terminals of the end-organ or of the cor- 
 tical cells. The variation, if it occurs, is very slight, 
 for no periodic increase or decrease in intensity of a 
 sensation from a physically constant stimulus con- 
 tinuously above the threshold is discernible.^ 
 
 The phenomena in question are therefore not 
 "fluctuations of attention^' in a sense in which that 
 expression would naturally be taken. If the at- 
 tention does actually shift from a sensation under 
 observation, the disappearance of the sensation can- 
 not be noted unless the disappearance comes be- 
 fore the shift or after the attention returns. Yet 
 the fluctuations are, in another sense, those of 
 "attention," for the essential condition of the ex- 
 periment is that the attention shall be to the image 
 of the presentation in the intervals when the sen- 
 sation is not intuited. 
 
 The difficulty of distinguishing between the sen- 
 sation and the image in the case where the stimula- 
 tion is minimal enormously complicates observa- 
 tion. In certain cases the observer is unable to 
 distinguish at all, as is shown by his continuing 
 to report the sensation long after the stimulus has 
 been suspended completely but gradually. In such 
 * This is true for auditory sensations, at least. 
 
318 A SYSTEM OF PSYCHOLOGY 
 
 cases the characteristic fluctuation cannot be ob- 
 tained; the sensation seems either present all the 
 time or absent all the time. 
 
 5. The Selective Fluctuations of Vividness 
 
 When several complexes are presented they are 
 apt to occupy the focus alternately. As I gaze at 
 the desk before me my attention is centred now on 
 the ink-bottle, nov^ on the pile of books, now on the 
 ink-bottle again, now on the drop-light, now on the 
 stack of letters. Even when I attempt to attend 
 continuously to the ink-bottle I find that I am at- 
 tending to it only for short periods, the focus being 
 occupied by various other things in the intervals. 
 Not visual presentations alone jostle the presenta- 
 tion of the ink-bottle. Auditory, tactual, olfactory, 
 and organic presentations take their turn. Ideas 
 also flip in and out to the detriment of my study 
 of the ink-receptacle. 
 
 This periodicity of focal consciousness is one of 
 its most uniform characteristics. In general, we 
 can attend to anything only by a succession of short 
 periods. This holds for ideas, of course. Try to 
 think of any one thing and see how intermittently 
 you succeed. 
 
 Many striking illustrations of the selective flue- 
 
THE TIME RELATIONS OF CONSCIOUSNESS 319 
 
 tuations of attention are easily available. Retinal 
 rivalry is one such. Place in a stereoscope two sim- 
 ple pictures which are radically different; a num- 
 ber of concentric circles in one, and a number of 
 parallel lines in the other; or two large letters, or 
 two fields of different colors. On looking through 
 the stereoscope in the usual way — one eye seeing 
 each card — it will be found that the two figures or 
 two colors are seen alternately. Sometimes both 
 of two colors will be seen, but in different parts of 
 the field, or parts of both diagrams will be seen 
 simultaneously.^ 
 
 The "stair-case figure,^' "tumbling block figure,'' 
 and other illusions of "reversible perspective'' are 
 also illustrations of fluctuations of attention. These 
 are simple figures so drawn that the space relations 
 are ambiguous. Thus, in Figure 13, the skeleton 
 chair may be seen either facing you or facing away 
 
 * If the two pictures are so arranged that no detail of one 
 occupies a retinal point corresponding to a point of the other 
 eye, occupied by a detail of the other picture, the two may 
 combine. Thus, if a figure before one eye has an open space 
 in the centre, and a smaller figure be presented to the retinal 
 area of the other eye corresponding to this space, the figures 
 may be seen combined. Some observers report binocular 
 color combinations; red presented to one eye, and blue to the 
 other, giving purple, etc. But this observation may for the 
 present be doubted. Complementary colors will give gray, 
 because adaptation to the two takes place rapidly. 
 
320 
 
 A SYSTEM IN PSYCHOLOGY 
 
 from you. After seeing it both ways it is practically 
 impossible to see it either way continuously. At- 
 tempts have been made to connect these changes 
 with eye-movements, or spatial shifts of attention, 
 i. e,y from one point of the figure to another. At 
 certain times the chair will face you while you at- 
 
 y 
 
 
 
 
 ^L 
 
 ( 
 
 1 
 
 / 
 
 
 / 
 
 
 Q 
 
 
 J 
 
 
 a 
 
 
 Fig. 13. 
 
 tend to the corner at a, and reverse its position when 
 your attention shifts to b. This is as if the point 
 fixated tends to become the near point. But the 
 same shift of perspective may be produced with the 
 opposite shift of attention; all depends on which 
 habit is formed. In general, any such objective way 
 of determining a shift of the perspective operates 
 through association. You expect to see the figure 
 in a certain position when a certain change is made. 
 
THE TIME RELATIONS OF CONSCIOUSNESS 321 
 
 or you have uniformly observed it in a certain posi- 
 tion with a certain direction of attention. Hence, 
 the result. 
 
 The percept based on the lines of the reversible 
 perspective figure is largely reproduced. The sim- 
 ple lines of figure 13, for example, are associated 
 with other features of chairs in both positions equally 
 well. We have, therefore, a selective fluctuation of 
 the two reproduced factors, first, one uniting with 
 the presented content, and then the other taking 
 its place. The exact moment of the transformation 
 may be determined by such factors as shift of eye 
 in any direction, provided the shift has become 
 associated with that particular change. 
 
 Figures 14 and 15 show a sort of fluctuation akin 
 to that of the reversible perspective figures. After 
 looking carefully at a and h (of either figure), c 
 alone will probably be seen alternately with the 
 aspect of a and &. 
 
 Fluctuations of perception based on ambiguous 
 impressions of senses other than visual might be 
 produced. These ambiguous impressions are, how- 
 ever, not so simply obtainable in the other sense- 
 realms. One experiment may be made in the fol- 
 lowing way: Obtain a revolver with round barrel 
 and a bottle having a neck of the same diameter 
 
322 
 
 A SYSTEM OF PSYCHOLOGY 
 
 and thickness as the muzzle of the revolver. Press 
 the muzzle of the revolver and the mouth of the 
 bottle alternately on the temple of the subject (first 
 
 Fig. 14. 
 
 Fig. 15. 
 
 removing the cylinder of the revolver!), allowing the 
 subject to see the object each time. Then, with 
 the subject's eyes closed, press either one against 
 the temple and in many cases he will perceive the 
 ring of pressure and temperature sensations alter- 
 nately as the pistol and as the bottle. 
 
THE TIME RELATIONS OF CONSCIOUSNESS 323 
 
 6. The Conditions of Constant Attention 
 
 Constant attention to one object in a normal con- 
 dition means one of two things: either the object 
 is intermittently in the focus or else the object in- 
 volves several discriminable details which occupy 
 the focus alternately or in succession. To attend 
 in actual continuity to a bare sound or color, even 
 to one of considerable intensity, is impossible. 
 But the sensation may persistently return to the 
 focus after each ousting, and the results be prac- 
 tically the same as if it had occupied the focus con- 
 tinuously. In the case of a more complex object, 
 as the ink-bottle on your table, you find, as we al- 
 ready have noted, your attention shifting from 
 feature to feature. 
 
 The strongest determinant of persisting recur- 
 rence is emotional coloring. That which you de- 
 sire or hate or love, etc., dwells long (with due re- 
 gard to the principle of intermittence) in the focus 
 of attention. The naturalist may observe for hours 
 a certain small animal because he has a strong 
 emotional interest in it and in its relation to certain 
 other animals. His attention courses rapidly over 
 a great many details, and many factors related to it, 
 but comes back again and again to the same features. 
 
324 A SYSTEM OF PSYCHOLOGY 
 
 It may be asked, " Why does not the boy continue 
 to attend to his Latin lesson, since he hates it?^^ 
 The answer is that he really does not hate it: it has 
 not even that vital emotional interest for him. It 
 deadens his emotions in so far as he attends to it, 
 and, hence, he does not attend, except as far as the 
 fear of consequences or desire of reward, or pride, 
 or some other emotional state may supply the neces- 
 sary coloring. Give the boy something he hates — 
 a boy rival, a hysterical teacher — and he will attend 
 to that object with ease and persistence. 
 
CHAPTER XIX 
 
 THE SUBCONSCIOUS 
 I. The Lower Limit of Vividness 
 
 A SENSATIONAL object may be reduced enor- 
 mously in vividness by the change which we describe 
 as passing from the focus into median conscious- 
 ness, and yet the intensity of the sensation be little, 
 if any, reduced. This fact suggests the question 
 how far this reduction of vividness may be carried. 
 There are two forms of this question: (1) May a 
 sensation of zero vividness exist? A sensation of 
 zero vividness would be one of which no person is 
 conscious at all. This question is strictly meta- 
 physical, and although it is possibly the most 
 fundamental of all the questions concerning con- 
 sciousness, we cannot consider it here. (2) May 
 a sensation be so reduced in vividness that analytic 
 consciousness of it is impossible? An affirmative 
 answer to this question would involve the admission 
 that there might be consciousness of the given sen- 
 sation in a complex of which it is a part, although 
 
 the sensation is not capable of being singled out 
 
 325 
 
326 A SYSTEM OF PSYCHOLOGY 
 
 therefrom. There can be no doubt as to the ex- 
 istence of sensational objects in this condition, and 
 it is to this condition that the term "subconscious'^ 
 is properly applied. The term " subconscious'' has 
 been much misused of late by quasi-psychologists 
 and by physicians, and it has been made to cover 
 a multitude of bizarre and absurd theories; hence, 
 the conception of a psychological subconsciousness 
 needs our careful consideration. 
 
 2. What the Subconscious is Not 
 
 Popular writers tend to confuse the subconscious 
 with the conditions of automatic and reflex move- 
 ments. Because a complex action, such as walk- 
 ing or knitting, is learned through consciousness 
 of the details of the action, and is later performed 
 without consciousness of these details, the details, 
 it is said, have been turned over to the "subcon- 
 scious." Of course this is true if by subconscious- 
 ness we mean simply that which is below the level 
 of consciousness, and certainly these details are 
 taken care of by physiological mechanisms which 
 do not require consciousness to direct them. The 
 authors to whom we refer really mean more than 
 this, and conceive of a lower level of consciousness 
 attending to the whole mass of such automatic ac- 
 
THE SUBCONSCIOUS 327 
 
 tions. There have not been lacking enthusiasts 
 who have considered digestive functions and the 
 growing of the nails as supervised by this subsidiary 
 consciousness. 
 
 Another misuse of the concept of subconscious- 
 ness is to consider it as the repository of forgotten 
 ideas. The remarkable fact that something which 
 has not returned to consciousness for a long time — 
 some incident of childhood, for example — may at 
 any time come back, has led the wilder theorizers 
 to suppose that all content is contained in the 
 " mind'' in very much the same form in which it was 
 originally in consciousness. The normal conscious- 
 ness, they say, includes but a small part of the total 
 field. The vast remainder is in subconsciousness. 
 Recollection is, accordingly, only the movement of 
 an idea from subconsciousness into consciousness. 
 The idea existed in your mind during the interval 
 when it was forgotten. 
 
 It is absolutely necessary for the student to rid 
 himself of all such fantastical notions. Content 
 forgotten is in general not in any sort of conscious- 
 ness, although it may have its effects in present 
 consciousness. The learning of motor-adjustments 
 is the process of turning those adjustments over to 
 mechanisms which need no conscious supervision. 
 
328 A SYSTEM OF PSYCHOLOGY 
 
 3. The Two Sorts of Marginal Consciousness 
 As I sit here writing I do not consciously hear the 
 ticking of the clock. Yet, if the clock should stop 
 I would be aware of the stopping. I may be so 
 absorbed in my task that if the clock strikes I do 
 not notice it at the time. But several minutes later 
 I may recall the striking and in memory count the 
 strokes. 
 
 We are constantly subjected to stimuli of all sorts 
 which give rise to sensations, but these sensations 
 do not rise to any considerable degree of vividness. 
 In the vast majority of cases these sensations and 
 sensation-complexes cannot be recalled or remem- 
 bered unless unusual means are employed. Nor- 
 mal recall, as we have explained, depends princi- 
 pally on association, and association depends on 
 vividness. Various means for the recall of what 
 was perceived marginally or subconsciously may 
 be employed. For example, the subject may be 
 hypnotized, and, when questioned in that state, may 
 give evidence of the recall of percepts which he 
 did not notice at all. The subconscious percepts 
 may be obtained, in the first place, by calling his 
 attention strongly to some visual object to which 
 he turns the line of regard, and simultaneously 
 
THE SUBCONSCIOUS 329 
 
 displaying some object in peripheral vision. In 
 the hypnotic state the subject may describe the 
 object which he did not know that he saw. The 
 theorists have explained this by saying that by 
 hypnosis the subconscious part of the mind is made 
 conscious. This really amounts to saying that we 
 don't know as yet how the phenomena are pro- 
 duced. The recall of subconsciously perceived ob- 
 jects may occur in a reverie or in the pathological 
 state of "crystal gazing.^' In the latter state the 
 subject, thrown into a state of light hypnosis by 
 gazing fixedly into a crystal sphere or a bowl of 
 water held close to the eyes, obtains visual hallu- 
 cinations in which former percepts, subconsciously 
 perceived, appear. Another aid to the recall of 
 subconsciously perceived objects consists in show- 
 ing the subject a part of the former object, which 
 may recall the remainder of the details, since asso- 
 ciation of a certain strength is established even at 
 the low vividness of the subconsciously perceived 
 object. 
 
 In none of these cases is it necessary to assume 
 a subdepartment of consciousness in which the per- 
 cepts are held over between the original perception 
 and the recall. The contents are perceived, dis- 
 appear, and are recalled just like any percepts, ex- 
 
330 A SYSTEM OF PSYCHOLOGY 
 
 cept for the fact that the low vividness of the per- 
 ception makes recall difficult. 
 
 The effect of the subconscious perception may 
 be demonstrated, even when recall is impossible. 
 If you present to a subject a number of cards con- 
 taining simple marks or designs, some of which he 
 has previously seen subconsciously, and if you ask 
 him to choose several from the number, he will be 
 apt to choose the ones which were previously seen. 
 The above are typical experimental procedures for 
 demonstrating the existence of subconscious per- 
 ception. 
 
 The second sort of marginal consciousness is 
 rather hypothetical. If it exists, it is the content 
 produced by stimulation which is so low in intensity 
 that it cannot be vivid even under the best normal 
 conditions. A sound, for instance, may be so 
 weak physically that it cannot be perceived, al- 
 though the air-waves are actually causing nerve- 
 excitation in the ear. This is shown by the fact 
 that the sudden stoppage of a very weak (physical) 
 tone may be clearly perceived, even though the tone 
 itself may have been imperceptible. It may be 
 said that the tone was in marginal consciousness, or 
 subconsciousness, and this view is supported by 
 the introspection of the persons taking part in such 
 
THE SUBCONSCIOUS 331 
 
 experiments. What is heard at the moment of the 
 interruption of a stimulus is described as the cessa- 
 tion of a tone, and not simply some disturbance 
 which might be taken to mean the cutting off of 
 the stimulus. The interpretation of these phenom- 
 ena and similar phenomena in other sense-realms 
 is beset with difficulties; neither the arguments for 
 the subconscious explanation nor the objections to 
 it are very weighty. Hence, the matter is best re- 
 garded as a problem for experimentation rather 
 than for theorizing. 
 
 4. Multiple Personality 
 
 The strongest impulse to postulate a subcon- 
 sciousness of the sort we are unwilling to admit 
 comes from certain phenomena of abnormal psy- 
 chology which are known as "alternations of per- 
 sonality" or " multiple personality." In some cases 
 a patient may suddenly forget the events of his past 
 life and lose the habits and traits of character 
 which previously have distinguished him. He be- 
 comes by this rapid transformation a man of an 
 entirely different sort; he may call himself by an- 
 other name; we may say he has a new personality. 
 The patient may continue for months in his new 
 life, and then suddenly his former memories may 
 
332 A SYSTEM OF PSYCHOLOGY 
 
 return, and with their return the memory of the 
 intervening months be lost. He returns to the first 
 personality and knows nothing of the second. 
 After a longer or shorter time the patient may re- 
 lapse into the second personality, remember now 
 all that occurred when he had this personality, and 
 forget both periods of the first. The two person- 
 alities may continue to alternate, or, in other words, 
 the person may continue to alternate between the 
 two conditions. There may be three or more dis- 
 tinct personalities involved and the conditions in 
 regard to memory may be much more complicated 
 than in the case which we have just described. The 
 patient, for example, when he has personality No. 1 
 may know^ nothing of what has occurred when he 
 had either of the other personalities. But when he 
 has personality No. 3 he may remember perfectly 
 all that happened while he was in the other two 
 states. He may insist that the experiences in states 
 1 and 2 were not his experiences, but were the ex- 
 periences of some other person. 
 
 If we conclude, as some psychologists have done, 
 that the different abnormal personalities exist simul- 
 taneously, and that sometimes one, sometimes an- 
 other, gets the upper hand, forcing the experiences, 
 memories, and processes forming the others out of 
 
THE SUBCONSCIOUS 333 
 
 consciousness, either as subconscious or co-con- 
 scious states, the statement of the case from the 
 point of view of pathology and therapeutics is 
 simple. The personality of the individual appar- 
 ently has lost its organic unity, and has fallen 
 into two or more fragments which are loosely con- 
 nected with each other. If by the use of proper 
 means (as, e. g,, hypnosis) the fragments of the per- 
 sonality are reunited, the patient is cured. But 
 the hypothesis of co-consciousness gives us no real 
 information as to the actual significance of the 
 patient's symptoms, nor as to the actual processes 
 involved in the removal of the symptoms. 
 
 The acceptance of the subconscious or co-con- 
 scious explanation of alternating personality would 
 logically involve the acceptance of the same expla- 
 nation for the forgotten ideas of normal life. On 
 the other hand, we can state the facts of the aberra- 
 tions of memory in pathological cases without in- 
 volving the hypothesis of the unknown, just as 
 easily as we can state the conditions in normal cases. 
 In neither the pathological nor the normal cases is 
 it necessary to assume that forgotten ideas are car- 
 ried along in a co-consciousness during the period 
 in which they are not remembered. 
 
 As for the non-ideational factors involved in per- 
 
334 A SYSTEM OF PSYCHOLOGY 
 
 sonality — habits of action and emotion — the as- 
 sumption of a co-consciousness adds nothing to the 
 explanation of their appearance and disappearance. 
 To say that a man has a certain habit of speech, for 
 example, means simply that, as a matter of fact, 
 his vocal organs move in a certain way. If the 
 vocal organs cease to function in the way indicated, 
 and function in a different manner, the habit has 
 become non-existent. It cannot coexist with the 
 new habit, although the nervous mechanism may 
 not be so completely modified that it will not event- 
 ually return to its earlier condition and reinstate 
 the old habit. 
 
 It is true that a large part of habit is ideational; 
 the bodily functions are influenced by the processes 
 in representative consciousness. But an emphasis 
 on this aspect of habit simply brings us back to 
 the first problem: how to account for the ideas 
 which were in consciousness and may be in con- 
 sciousness again, but are out of consciousness at 
 present. 
 
 We are justified in concluding that the assumption 
 of a detached subconsciousness or co-consciousness 
 to explain the phenomena of alternating person- 
 ality is not at present defensible, since the idea- 
 tional problems involved in these phenomena are 
 
THE SUBCONSCIOUS 335 
 
 quite like those involved in all mental life, and the 
 problems of neural disposition and modification are 
 not affected in any way by the hypothesis of co- 
 consciousness. 
 
CHAPTER XX 
 
 THE EGO 
 
 Experience cannot be completely accounted 
 for in terms of bare consciousness and the content 
 alone. Experience of any content intrinsically 
 implies something experiencing that content. The 
 immediate fact of one^s own consciousness is always 
 something which may be expressed by the words, 
 " I perceive," " I feel," " I imagine," etc. The " I," 
 or real Ego, which is the essential centre of reference 
 for the whole of the content of consciousness, is not 
 itself a fact of content, and hence is not a feature of 
 psychological analysis: it is the one thing which, 
 as the subject, stands over against the whole of 
 objectivity, and hence, while not discovered by any 
 analysis, it is involved, not only in every attempt at 
 analysis, but in every bit of experience. 
 
 The celebrated formula of Descartes, Je pense, 
 done je suis, expresses what is immediately given 
 as a fact of experience. Thinking, in the Cartesian 
 terminology, is exactly synonymous with beiiig con- 
 scious in ours. What Descartes says is that con- 
 sciousness is intrinsically something which con- 
 
 336 
 
THE EGO 337 
 
 cerns an "I'' or "Ego": that there is no such thing 
 as impersonal experience. So far we must agree 
 with Descartes; but he follows this statement of 
 inevitable introspection with the assumption that 
 the "I" is a thinking substance^ and in this step we 
 cannot follow. 
 
 The '*!'' is not anything which can be defined 
 in terms of objectivity — as the metaphysical sub- 
 stance is necessarily defined. It is the pure subject, 
 which is uniquely and antithetically removed from 
 all objectivity, and which is yet involved in all ref- 
 erence to objectivity. 
 
 Any attempt at the discussion of the "I" involves 
 us in a maze of paradoxes. The "I" cannot be 
 discussed, because it is actually non-objective. It 
 has no qualities: and yet this very statement is a 
 quasi-qualitative ascription. The only unambigu- 
 ous statement we can make concerning it is that " I 
 experience" or "I am conscious." 
 
 There is a method of explaining away the "I" 
 sometimes adopted by psychologists, which consists 
 in assuming that content experiences itself. Thus, 
 one "state of consciousness" (using this term as 
 synonymous with the term "content") is assumed 
 to experience the state w^hich just precedes it in 
 time: or, one group of content factors is assumed 
 
338 A SYSTEM OF PSYCHOLOGY 
 
 to experience the remainder of the factors in any 
 given content. The subject, in accordance with 
 this theory, is identified with one portion of the 
 content, and the other portions of content are de- 
 scribed as the apprehended objects. There are 
 several other forms of the content-subject hypoth- 
 esis. One form of the hypothesis does not sup- 
 pose a definite part of the content functioning at a 
 given time as the subject, but simply assumes in a 
 more vague way that the varying details of the con- 
 tent which is present at a given moment are present 
 by virtue of being in a definite sort of mutual re- 
 lationship. This relationship constitutes at once 
 the consciousness and subjectivity: it is subjectivity 
 without a subject. 
 
 These views assume at once more and less than 
 experience gives us. They assume, in the first place, 
 a relationship in content which we cannot find there. 
 That I experience a certain red may be defined as 
 a relation between red and the other factors of con- 
 tent, and we do actually experience relations in this 
 connection; but the relations we find in the con- 
 tent are all relations which determine the red as it 
 is experienced, and are none of them, severally or 
 together, identifiable as the experience. On the 
 other hand, these theories simply ignore the fact 
 
THE EGO 339 
 
 that in searching the content for any sort of relations 
 we are assuming a point of view totally outside the 
 content from which to make the inspection. This 
 omission is much the same as that which is made by 
 those philosophers who claim that the universe is 
 just one substance, which, looked at in one way is 
 called matter, and looked at in another way is 
 called mind. They fail to see that the point of view 
 from which the one substance is looked at, now this 
 way and now that, is something assumed in addi- 
 tion to the one substance; if substance is strictly 
 one, and if there is nothing else, it can look at itself 
 from only its own single point of view. When we 
 try to make consciousness depend on content alone 
 we are neglecting the fact that we are now repre- 
 senting consciousness from an outside point of view 
 and have not given a fair account of conscious- 
 ness till we indicate how we got to this point. If 
 we represent this consciousness in any sort of sym- 
 bolic way, as we may represent content, it is ijpso 
 facto not adequate, because we still are assuming 
 a consciousness of the symbolization without which 
 it is impossible. 
 
 We are obliged to assume, then, a point of view 
 or point of reference over against content; perhaps 
 the '* transcendental unity of apperception" of 
 
340 A SYSTEM OF PSYCHOLOGY 
 
 Kant; and it is just the orientation to this point of 
 view which constitutes consciousness. It, of course, 
 cannot be symbolized or described, because as soon 
 as it is described it becomes no longer the point of 
 view to which the consciousness refers. 
 
 We speak of this transcendental point of view as 
 " I/^ The " I,'* if we accept the fact of it, must not 
 be supposed to be active. Activity of any sort is 
 an objective fact and is in the objective world. 
 The "I" is the pure subject and is incapable of 
 anything except being a subject. 
 
 It may be asked, of what use is it to suppose the 
 ^*I," which has no qualities, cannot be analyzed or 
 scrutinized, and can do nothing; and, also, if it is 
 not describable or scrutinizable, how can we know 
 it is there. The answer to both questions is, that 
 the "I^* is of no use, but that our analysis of the 
 content of consciousness presupposes it, and hence 
 we admit it. We do not observe the Ego, but it 
 is involved essentially in every observation. It is 
 really the only thing that observes or is conscious : 
 hence, it has immediate claim to existence. 
 
 The view outlined above is believed to be that 
 from which a satisfactory and adequate account 
 of consciousness can be given. It is a view which 
 is much older than modern civilization, but fits 
 
THE EGO 341 
 
 in as acceptably with scientific psychology as with 
 ancient philosophy and religion. It is the only view 
 which completely justifies the universal practice of 
 modern psychology in leaving the " I/' or Ego, out 
 of its analysis; for if the Ego were not transcen- 
 dental it would have to be treated analytically in 
 psychology, instead of being merely assumed. Be- 
 ing transcendental, the Ego has practically no in- 
 terest for psychology or science. 
 
 Modern psychology is truly said to be psychology 
 without a soul, but if the transcendental point of 
 reference or subject is what is meant by the term 
 soul, psychology not only does not deny the soul, 
 but positively aflSrms it. We must, however, bear 
 in mind the fact not only that we can know nothing 
 about the Ego, but that there is nothing to be known 
 about it. 
 
CHAPTER XXI 
 
 THE OCCULT 
 I. The Study of the Occult 
 
 In discussing the transcendental Ego we were 
 upon dangerous ground. So much bias exists 
 among those persons whose fields run into that of 
 psychology that it is impossible to make any state- 
 ment, however judicious, concerning the Ego with- 
 out incurring the antagonism or contempt of some 
 of these individuals. The same conditions sur- 
 round us in the discussion of the occult. It is quite 
 noticeable that writers who have expressed opinions 
 on this subject have met with a great deal more than 
 intellectual dissent from their opinions. Especially 
 unpleasant has been the position of those who 
 have agreed with none of the extreme views on 
 psychic research, and in consequence have been 
 denounced from all sides. This explanation is 
 necessary in order that the student may know that 
 what is set down in this chapter is not apt to be 
 
 approved by even a considerable minority of rep- 
 
 342 
 
THE OCCULT 343 
 
 utable scientists, to say nothing of the vast com- 
 pany of fanatics. 
 
 Just what is here meant by the occult, the reader 
 will gather as he proceeds. The things treated 
 under this heading are properly the subject-matter 
 of what is called psychic research, but in one way 
 or another are also interesting and important for 
 psychology. Psychic research is at present in dis- 
 repute among scholars, largely because psychic re- 
 searchers do not take a logical psychological attitude 
 toward the phenomena they investigate. Psychic 
 research, the investigation of phenomena which are 
 alleged to be not in accordance with accepted views 
 of natural law, is a perfectly legitimate activity. Its 
 purpose is two-fold: first, to accumulate data for 
 psychological study; and second, to rout rascals and 
 to dispel popular superstition. 
 
 2. Telepathy 
 
 It is popularly believed that the thoughts of one 
 person may directly influence those of another. 
 This belief is somewhat akin to the ancient super- 
 stition that the eye of one person is able to affect 
 another person. Vision is sometimes called touch 
 at a distance, and it is hard for the savage (and 
 
344 A SYSTEM OF PSYCHOLOGY 
 
 philosophical savages are still extant) to believe 
 that when his eye rests upon another person or ob- 
 ject something does not go out from his visual 
 organ to take in the percept of the other, much as 
 his finger would be stretched out to get a tactual im- 
 pression. From this naive conception of the phys- 
 ics of vision the belief in the evil eye probably 
 arises, and from it comes also the harmless super- 
 stition of the present day, that one person can attract 
 the attention of another by gazing intently at the 
 back of his head. It is possible that the fully de- 
 veloped eye-power superstition involves the alleged 
 phenomena or thought-transference, as well as 
 the supposed power of the eye itself. Telepathy, 
 which is believed in by many persons at the present 
 time, is the (alleged) effect produced on the con- 
 sciousness of one person by the mental operations 
 of another. 
 
 As a matter of fact, we have been able to discover 
 no communication between persons except that 
 which takes place through what we call the physical 
 world. I may have the sensation which you have 
 if I am subjected to the same stimulus. I may 
 think of the object of which you are thinking if 
 some common perception is associated with the 
 object in each of us. By a perfectly definite chain 
 
THE OCCULT 345 
 
 of association two or more persons often arrive with 
 approximate simultaneity at the thought of some- 
 thing which has not been directly mentioned. If, 
 however, one person thinks of a certain object 
 because another thinks thereof, the thought of the 
 second person must have expressed itself in some 
 objective sign which was perceived by the first per- 
 son, and which aroused the thought of the given ob- 
 ject by normal association. 
 
 Certain interesting phenomena which are com- 
 monly designated by the term ^* mind-reading^' 
 offer confirmation of this conclusion. Mind-read- 
 ing is frequently undertaken as a parlor amuse- 
 ment, and some of the most striking results are ob- 
 tained by amateurs. A subject may be sent from 
 the room while the remainder of the company de- 
 cide on some act he is to perform on returning. 
 The subject is brought in by two of the company 
 acting as guides, usually with their hands on the 
 shoulders of the subject. All the company think 
 intensely of the appointed action, and the subject in 
 many cases proceeds to perform it, after more or 
 less delay. 
 
 Variations may be introduced into such an ex- 
 periment which prove that the subject perceives 
 (usually marginally) slight pressure sensations from 
 
346 A SYSTEM OF PSYCHOLOGY 
 
 the hands of the guides, which, by association, bring 
 up the idea upon which the designated action fol- 
 lows. As might be suspected, the experiment suc- 
 ceeds best when the subject is convinced that he is 
 receiving mental influence, and fails when he at- 
 tempts to interpret pressure sensations consciously. 
 Not all persons succeed as subjects; a condition of 
 mental equilibrium is required in which slight 
 associations may be effective; a condition not easily 
 obtained by every one. 
 
 Sometimes the mind-reading succeeds when there 
 is no contact between the subject and any one else. 
 Such cases are very few, the professional demon- 
 strations being pure humbug. In the few cases 
 that are genuine, the subject is able to interpret 
 changes in the breathing of the company as signs 
 that he is starting to do the right or wTong thing, or 
 else is guided by faint sounds made by the vocal 
 organs of those thinking of what he is to do. The 
 majority of adults partially articulate words in 
 thinking, and this slight vocal action occasions air- 
 waves which may affect the ears of the subject, and 
 thus produce the effects subconsciously. If the 
 subject be blindfolded and have the ears stopped 
 (a diflBcult condition to obtain, by the way), mind- 
 reading without contact will in no case succeed. 
 
THE OCCULT 347 
 
 There is a wide-spread belief that in hypnosis the 
 patient is responsive to the thoughts of the hypno- 
 tizer. The phenomena of hypnotism are some- 
 times described in terms of the influence of one 
 mind on another, but this influence is always pro- 
 duced in the normal way — by physical signs. The 
 hypnotizer may think as much and as intensely as 
 he pleases, and the patient will not fathom his inten- 
 tion unless he gains some inkling of the thought by 
 visual, auditory, or other sensations. In certain 
 cases the hypnotized patient may interpret signs 
 more readily than does the normal subject, but such 
 is not always the case. The exact nature of the 
 hypnotic state is not yet clearly understood. The 
 ideas suggested by the hypnotizer occupy the pa- 
 tient's mind, driving out any which are conceptually 
 incompatible with them, and, if they are ideas of 
 action, the actions follow mechanically according to 
 what we would expect under the principle of ideo- 
 motor activity when all checks and inhibitions are 
 removed. This description of the hypnotic state 
 does not explain it. 
 
348 A SYSTEM OF PSYCHOLOGY 
 
 3. Mysticism 
 
 Closely related to the theory of telepathy is the 
 doctrine of mystic knowledge. This doctrine, which 
 is found in the writings of many modern men of 
 letters, comes to us directly from the Neoplatonic 
 philosophy of the so-called Alexandrian school. 
 The writings formerly ascribed to Dionysius the 
 Areopagite, but now admitted to belong to the 
 fifth century, embody the Neoplatonic doctrine 
 in its characteristic form; and these writings, trans- 
 lated and studied by the scholastic philosophers, 
 have been the direct sources of mediaeval and mod- 
 ern mystical beliefs. 
 
 In brief, mystic knowledge is supposed to be a 
 form of cognition absolutely different in character 
 from sense perception and intellectual apprehen- 
 sion, and vastly superior to these. In ecstasy, which 
 is the technical name for the act or state of mystical 
 knowledge, the subject is alleged to be in direct 
 contact with some form of ultimate reality. In 
 Maeterlinck^s system, this ultimate reality, which the 
 soul is supposed to know or experience in this mystic 
 way, may be another soul: in the original system, 
 and the system of certain other modern mystics, 
 the reality which is experienced is the Divine Being. 
 
THE OCCULT 349 
 
 The nature of this mystic knowledge is, according 
 to the theory, indescribable, because it is entirely 
 removed from the sphere of ordinary knowledge, in 
 which sphere only are descriptions and explanations 
 possible. The statement which comes nearest to 
 the mystic's doctrine, is that in ecstasy the soul is 
 united w^ith God ( or with another soul). 
 
 The mystic experience must be carefully dis- 
 tinguished from the seeing of visions or the hearing 
 of voices (as in the case of Joan of Arc), and from 
 the " feeling of the presence'' of some one — a feeling 
 in which many people believe. The mystic experi- 
 ence is not at all the acquirement of the ordinary 
 form of knowledge in a mysterious way: it is an ex- 
 traordinary form of knowledge. The experiences 
 which approach this condition, but which remain 
 in the ordinary sphere, may be conveniently desig- 
 nated as pseudo-mystical. 
 
 With the claims of mysticism psychology has 
 strictly nothing to do. When some one tells me 
 that he has had a kind of experience which has 
 absolutely no relation to my experience, I have 
 as little ground for admitting the truth of his state- 
 ment as for denying it. Nevertheless, when the ex- 
 perience of another person can be satisfactorily 
 explained in terms of our own experiences, we must 
 
350 A SYSTEM OF PSYCHOLOGY 
 
 provisionally explain it in that way. The mystic 
 distinctly tells us that in ecstasy there is conscious- 
 ness — but no perception or imagination or intellec- 
 tual process. From which we conclude that the 
 experience — if it really occurs — is of pure feeling. 
 This conclusion we believe to be satisfactory and 
 final. 
 
 4. Spiritualism and Mediumship 
 
 A large and varied assortment of performances 
 and superstitions have come to be included under 
 the name of spiritualism or mediumship. Me- 
 diums, or "psychics/' or clairvoyants, pretend to 
 produce table-tipping, slate-writing, playing on 
 musical instruments, and other physical phenomena 
 without ordinary physical means. They read the 
 future and the past, and put you in communication 
 with Julius Csesar, or Flashing-Eyes the Indian 
 maiden, or your great-grandfather. A few words 
 about these performances are appropriate here. 
 
 In the first place, supernatural mediumships — 
 the production of physical effects without adequate 
 physical causes — must be excluded from the dis- 
 cussion. The table-tippings, slate- writing, "spirit- 
 photographs, " and other tricks have been explained 
 and exposed until they have become merely a 
 
THE OCCULT 351 
 
 source of weariness. Every supernatural medium 
 who has been carefully investigated has been found 
 to be a fraud. All the tricks of the psychics have 
 been done by Kellar and the stage magicians, and 
 many of the performances of these men have defied 
 the investigation of scientists, until the magicians 
 themselves have furnished the explanations. 
 
 The production on slates or other surfaces of 
 writing or pictures which are claimed not to have 
 been produced by natural hands and processes, is 
 conclusive proof of fraud. When a medium causes 
 a table to tip or rise into the air, apparently without 
 physical aid or support, or causes voices to sound or 
 instruments to play, which voices and which play- 
 ing are claimed not to be the medium's or her as- 
 sistants', she brands herself as a humbug. The 
 materialization of a spirit is convincing evidence 
 that the medium presumes on the crassest credulity 
 on the part of her patrons. 
 
 In other cases, the mediums are possibly honest. 
 Psychic healers who claim to heal broken bones or 
 bacterial diseases by mental treatment, sometimes 
 when the patient does not know that he is being 
 treated, may think they can perform these miracles. 
 People have always believed in witchcraft and 
 sorcery, and the sorcerers themselves, whether voo- 
 
352 A SYSTEM OF PSYCHOLOGY 
 
 doo doctors or "Christian Science" practitioners, 
 are usually ignorant enough to share the belief. On 
 the other hand, the psychic treatment of nervous 
 disorders is an established and valuable method, 
 the "mental'^ state of the patient having a profound 
 effect on his "bodily" functions. Psychotherapy is 
 employed by scientific physicians, and it may often 
 be employed by the most ignorant sort of charlatans 
 with great success. If the patient thinks that he is 
 receiving treatment and is being benefited, the 
 benefit frequently follows. 
 
 Psychic treatment cannot take the place of other 
 sorts of medical treatment where these are indicated. 
 In diseases of other than nervous origin the patient's 
 state of mind is important, but its importance is 
 relatively small. Many patients, of course, get well 
 without medical attention — physicians do not claim 
 to "cure" any disease, but simply to assist nature 
 in its fight against it — and many cases occur in 
 which the patient thinks he has a disease from which 
 he is really free, and, upon feeling better, he may be 
 of the opinion that he has been cured of that disease. 
 Hundreds of cases of cures by " Christian Science," 
 which are described as having been cured after the 
 patients had been given up by the doctors to die of 
 a disease, have been investigated, and in not one 
 
THE OCCULT 353 
 
 case out of fifty has it been found that such a diag- 
 nosis had actually been made. 
 
 In natural mediumships there is no pretence of 
 effects produced in a supernatural way. If writing 
 and other phenomena are produced, they are the 
 work of the medium, and no claim is made to the 
 contrary. The only question at issue is as to the sig- 
 nificance of what is written or spoken by the medium. 
 
 The natural mediums usually claim that what 
 they have to communicate comes from the "spirits" 
 — a "spirit" takes control of the hand or the vocal 
 organs of a medium and expresses itself by means 
 of them. This hypothesis would explain some of 
 the remarkable things which have been " communi- 
 cated" by certain mediums, if it were not for the 
 fact that we don't really know what we mean by the 
 term "spirit." The "spirits" would seem to be 
 decaying fragments of former personalities, since 
 their communications are usually trivial, and mixed 
 with much pure rubbish. For the present it is 
 safest not to adopt any hypothesis whatsoever for 
 the explanation of natural mediumship, but to hold 
 the few remarkable results of experiments with 
 mediums as interesting data requiring much to be 
 added before any explanation can be attempted. 
 It is by no means impossible that it may all be ex- 
 
354 A SYSTEM OF PSYCHOLOGY 
 
 plicable as chance and cheating. The societies 
 for psychic research have for a long time been en- 
 gaged in investigating all cases of mediumship which 
 seem geniune, but have received little recompense 
 for their labors. Certainly they have learned noth- 
 ing about the future life — the existence of persons 
 after what we call death. 
 
 It is to be noted that the natural mediums who 
 have seemed genuine can be counted on the fingers. 
 By genuine is here meant that they are not con- 
 sciously trying to deceive: that the information they 
 furnish comes from a source unknown to themselves. 
 The large body of professional clairvoyants, sooth- 
 sayers, and psychics is simply a group of impostors. 
 
REFERENCES 
 
 The student is urged to compare the view-points and 
 interpretations of the foregoing treatise with those of 
 other texts. The most important shorter treatises are : 
 Ward, article, "Psychology/' in the Encyclopaedia Bri- 
 tannica, eleventh edition; Angell, Psychology; Titchener, 
 Text-Book of Psychology; Kiilpe, Outlines of Psychol- 
 ogy, and Maher, Psychology, The important longer 
 ones are: Ladd and Woodworth, Elements of Physio- 
 logical Psychology; Wundt, Grundziige der physio- 
 logischen Psychologic; Ebbinghaus, Grundziige der Psy- 
 chologic, and James, Principles of Psychology. The 
 last named is the most important of all in point of theory. 
 
 As a manual for the further study of the data of psy- 
 chology Ladd and Woodworth's book is especially to 
 be recommended. Recent books and articles on any 
 topic may be located by consulting the Psychological 
 Index, which is issued annually by the Psychological 
 Review, and contains all the titles for the year on psy- 
 chology, philosophy, and the relevant parts of neurology 
 and physiology. 
 
 Below are given a few references on points which are 
 emphasized in the foregoing treatise, some of the articles 
 being in agreement with our positions and some not. 
 
 On the Greek theory of the psyche: Turner, "Aris- 
 totle as a Psychologist," Catholic University Bulletin, 
 XVII, 299-317; Aristotle, De Anima (in Hammond's 
 Aristotle's Psychology), especially books I and II. 
 
 355 
 
356 REFERENCES 
 
 On the original use of the term psychology: Hamil- 
 ton, Lectures on Metaphysics, Lecture VIII. The defi- 
 nitions of the present science of psychology given in stan- 
 dard treatises do not differ much from the definition we 
 have given in chap. I, § 1. Stout, Manual of Psychol- 
 ogy, Introduction, chap. I, § 1, gives a definition which 
 is somewhat broader and possibly more accurate. The 
 definition given by Pillsbury, Essentials of Psychology, 
 does differ essentially from the orthodox one, and might 
 be made the basis of a distinct sort of psychology. Pills- 
 bury, however, virtually abandons his definition, ^nd 
 follows rather conventional lines. Kirkpatrick, Genetic 
 Psychology, approximates more nearly to a ^'behavior" 
 psychology. 
 
 On the restricted meaning of consciousness: Ham- 
 ilton, "Philosophy of Perception," in Discourses on Phi- 
 losophy and Literature, See also Mill, Examination of 
 Hamilton's Philosophy, chap. VIII. For a modern dis- 
 cussion of consciousness, see Hicks, "The Relation of 
 Subject and Object," Proceedings Aristotelian Society, 
 VIII (1908), 161-214. For a purely functional theory of 
 consciousness, see James, "Does Consciousness Exist?" 
 Journal of Philosophy, etc., I, 477-491. The title of 
 this article is, of course, not to be taken literally, but is 
 to be understood as questioning the validity of a certain 
 theory concerning consciousness. 
 
 On ELEMENTS of Content: Watt, "The Elements of 
 Experience," British Journal of Psychology, IV, 127- 
 204. 
 
 On the identification of sensation and brain proc- 
 ess: Loeb, Comparative Physiology of the Brain, chaps. 
 I, XV-XVIII, and especially IX; Forel, Nervous and 
 
REFERENCES 357 
 
 Mental Hygiene, chap. II; Pearson, The Grammar of 
 Science, chap. II, § 4. Many physiologists who prac- 
 tically adopt this view do not formulate it definitely. 
 Certain physiologists explicitly reject the theory: see 
 Howell, Physiology, pp. 182, 183. Certain others grope 
 in utter confusion, making absolutely no distinction be- 
 tween consciousness and object, or between matter and 
 either of these; see McNamara, The Evolution and 
 Function of Living Purposive Matter, in which the 
 paragraph in the middle of page 148 is typical of the 
 whole book. 
 
 For a clear statement of the parallel theory and 
 the arguments for it, see Mercer, Sanity and Insanity, 
 chap. III. An instance of the difficulty found by even 
 the best intentioned parallelists in actually maintaining 
 a position on the theory may be observed by attempt- 
 ing to interpret the section headed. The Appearance of 
 Consciousness, in chap. Ill of Angell's Psychology, in 
 the light of the statements made in the section headed 
 Terminology, in the same chapter. 
 
 For a statement of the interaction theory, see Ladd 
 and Woodworth, Elements, pt. III. James's Principles 
 is based on the interaction theory. 
 
 For Huxley's theory of the nature of matter, see 
 his essay on ^^The Physical Basis of Life," particularly 
 the latter portion thereof. On this problem, see also 
 Mill, Examination of Hamilton's Philosophy, chap. XI. 
 
 For the telephone theory of audition, see Ruther- 
 ford, ''The Sense of Hearing," Lancet, 1887, I, 2-6. 
 On the extensity theory: Ter Kuile, Pflilger's Archiv, 
 LXXIX, 146-157, 484-509; Dunlap, "Extensity and 
 Pitch," Psychological Review, XII, 287-292. 
 
358 REFERENCES 
 
 On MUSICAL scales: Ellis's translation of Helmholtz's 
 Sensations of Tone; Sabine, ^'Melody and the Origin of 
 the Musical Scale," Science^ N. S. XXVII, 841-847. 
 Naumann, History of Music (Praeger's translation). 
 
 On VISUAL SENSATION in general, the articles by Nagel 
 and by Von Kries in Nagel, Handbuch der Physiologie, 
 are especially to be recommended. See also Green- 
 wood, ^^Studies in Special Sense Physiology," in Hill, 
 Further Advances in Physiology (1909). On the 
 STREAMING PHENOMENA, scc Wohlgemuth, '* On the 
 After-Effect of Seen Movement," British Journal of 
 Psychology, Monograph Supplement No. 1. 
 
 On the variability of the temperature spots: Craw- 
 ford, "A Study of the Temperature Sense," Psycho- 
 logical Review, V, 63-112; Kelchner and Rosenblum, 
 Zeitschrift fur Psychologic, XXI, 174-182. 
 
 On the DISSOCIATION of dermal sensation qualities 
 by syringomyelia and other nervous diseases: Starr, 
 Organic and Functional Nervous Diseases. 
 
 On RELATIONS AS ELEMENTS OF CONTENT: Huxlcy, 
 
 Essay on Hume, chap. II; Woodworth, "The Conscious- 
 ness of Relation," Essays Philosophical and Psychological 
 in Honor of William James, 485-507; McGilvary, "The 
 * Fringe' of Wilham James's Psychology," Philosophical 
 Review, XX, 137-164. An interesting attempt at the 
 analysis of relations is contained in Spencer, Principles 
 of Psychology, second edition, II, chaps. XV-XXVI. 
 See also Brunschwig, Das Vergleichen und die Relation- 
 erkenntniss. The specific question as to the existence of 
 relation content is involved in the less sharply defined 
 question whether or not "imageless thought" exists, and 
 the two are sometimes confused. On imageless thought. 
 
REFERENCES 359 
 
 see Titchener, Lectures on the Experimental Psychology 
 of the Thought Processes, 
 
 On IMAGES AND IDEAS : Aristotle, De Anima, book III, 
 chaps. Ill and VII, On Memory and Recollection, and 
 On Dreams (in Hammond, Aristotle's Psychology); 
 Hamilton, Philosophy of Perception, foot-note on the his- 
 tory of the term idea; Alexander, "On Sensations and 
 Images," Proceedings Aristotelian Society, X (1909), 1-35; 
 Colvin, "The Nature of the Mental Image," Psycho- 
 logical Review, XV, 158-169; Angell, "Methods for the 
 Determination of Mental Imagery," Psychological Re- 
 vieWy Monograph Supplements, XIII (1), 60-108; Stout, 
 Manual of Psychology, book IV, chap. I. 
 
 On CONCEPT AND JUDGMENT: Mill, Examination of 
 Hamilton's Philosophy, chaps. XVII and XVIII. 
 
 On the PLATONIC "idea": Plato (Jowett's transla- 
 tion), Parmenides, 132, Phcedo, 100-106, Republic, book 
 VI, and especially book X, 596-598. (The numbers 
 are those in the margins.). 
 
 On association: Claparede, U association des idees, 
 and Calkins, "Association," Psychological Review, 
 Monograph Supplements, I, (2). 
 
 On space perception: Wundt, Physiologische Psy- 
 chohgie, sixth edition, II, cap. 13, § 5 and cap. 14, § 6; 
 Ribot, German Psychology of To-day, chap. IV; Sully, 
 The Human Mind, II, Appendices B and E; Kolben- 
 heyer, Die Sensorielle Theorie der optische Raumem- 
 pfindung ; Von Aster, "Beitrage zur Psychologic der 
 Raumwahrnehmung," Zeitschrift fiir Psychologic, 
 XLIII, 161-203. 
 
 On time perception: Montague,. "A Theory of Time 
 Verception,'' American Journal of Psychology , XV, 1-13; 
 
360 REFERENCES 
 
 Nichols, "ThejPsychology of Time/' same Journal, III, 
 453-527. Hamlin, " On the Least Observable Interval,'' 
 etc., same Journal, IV, 564-575. 
 
 On the question whether feeling is sensation or is sui 
 generis, and on the degrees of consciousness: Titch- 
 ener. Lectures on the Elementary Psychology of Feeling 
 and Attention, On the James-Lange theory of the emo- 
 tions, see James's defence, "The Physical Basis of the 
 Emotions," Psychological Review, I, 517-529. 
 
 On rhythm: Bolton, "Rhythm,'' American Journal of 
 Psychology, VI, 145-238; Stetson, "A Motor Theory of 
 Rhythm," Psychological Review, XII, 250-270, 293-350; 
 Dunlap, "Rhythm and the Specious Present," Journal 
 of Philosophy, etc., VIII, 348-354. 
 
 On the subconscious: Hart, "The Concept of the 
 Subconscious," Journal of Abnormal Psychology, IV, 
 351-371, gives an excellent outline of the theory we re- 
 ject; Jastrow, The Subconscious, presents implicitly a 
 theory which is even more extreme. 
 
 On ALTERATIONS OF PERSONALITY and multiple per- 
 sonality: Prince, The Dissociation of a Personality, pre- 
 sents an extreme view strikingly, and illustrates the fact 
 that a difBcult problem may be literally dramatized to 
 an apparently simple solution. Other standard books 
 are: Azam, Hypnotisme et double conscience, and Binet, 
 The Alterations of Personality, See also, in this connec- 
 tion, Janet, The Mental State of Hystericals, and The 
 Major Symptoms of Hysteria. 
 
 On the OCCULT in general, Lang, Psychic Research, in 
 the Encyclopaedia Britannica; and Moll, Hypnotism 
 (EngUsh from fourth edition, 1910), chap. XIII. On 
 MIND READING and telepathy: Moll, op cit., 62, 63, 455- 
 
REFERENCES 361 
 
 458, 510-519 ; Pf ungst, Clever Hans (Rahn's translation) ; 
 Hansen and Lehmann, "Ueber unwilkurliches Fliistern," 
 Philosophische Stvdien, XI, 471-530. Curtis, *' Auto- 
 matic Movements of the Larynx," American Journal of 
 Psychology, XI, 237-239. Laurent, ^*Les procedes des 
 liseurs de pensees," Journal de Psychologic, II, 481-495. 
 
 On mysticism: Underbill, Mysticism, gives the best 
 presentation from the mystic's point of view. Jones, 
 Studies in Mystical Religion, gives an historical account. 
 The writings of (the pseudo-) Dionysius the Areopagite 
 have been translated by Parker. The writings of Mae- 
 terlinck and of Emerson are good instances of the mod- 
 ern outcroppings of Neoplatonism which to a large 
 extent tincture all theological discourse of the present 
 day. See, for example, Maeterlinck, "The Awakening 
 of the Soul," and "On Women," in The Treasure of the 
 Humble; and Emerson's essay on The Oversold. 
 
 Questions concerning dreams must have been sug- 
 gested to the reader by several portions of our book, 
 but we have avoided this topic because so little is known 
 about it. Interesting speculations and controversies 
 concerning dreams are rife at present, but the state- 
 ments of these would be too long for this treatise. 
 The student may profitably read two books which rep- 
 resent the more scholarly attempt to study dreams: 
 Mourly Void, Ueber den Traum (Klem, editor), and 
 Foucault, La reve. A book which is having a great 
 vogue at the present time among medical men, and 
 which makes of an arbitrary theory a religious dogma 
 rather than a scientific hypothesis, is Freud, Traumdeu- 
 tung. See also Jones, "Freud's Theory of Dreams," 
 American Journal of Psychology, XXII, 283-308. 
 
INDEX 
 
 Accent in rhythm, 311 ff. 
 
 Achromopsia, 40, 67 ff. 
 
 Action: 265 ff. ; automatic, 274 ff.; 
 and the subconscious, 326; 
 habitual, 281 ff. ; ideo-motor, 
 267 ff . ; instinctive, 277 ff . , 282 f . ; 
 reflex, 254 ff. ; voluntary, 
 269 ff. 
 
 Adaptation, protective, 51, 74, 
 246. 
 
 iEsthesiometry, 140 f., 217. 
 
 Affective content, 243; and at- 
 tention, 323 f. ; in mediate as- 
 sociation, 186; and the self, 
 287. 
 
 Affective elements, 14, 242; in 
 emotion, 15, 255 f. 
 
 After-images; distinguished from 
 secondary sensations, 31 f.; 
 negative, 76. 
 
 Ageusia, 39, 48. 
 
 Algo-hedonic tone, 263 f. 
 
 Alterations of personality, 291. 
 
 Alternation of personalities, 331 ft'. 
 
 Amblacusia, 144 f. 
 
 Anatomy, 8 ff. 
 
 Anosmia, 39, 46. 
 
 Apperception, 198. 
 
 Appetition, 242 f. 
 
 Apprehension, 16. 
 
 Aristotle's theory of imagination, 
 16, 161, 153 ff. 
 
 Art, aim of, 257 f. 
 
 Association; intellectual, 186 f.; 
 mediate, 185 f., 190; physio- 
 logical basis of, 194 ff.; and 
 perception, 209 ff. ; principles 
 of, 180 ff.; and recall, 178 f.; 
 and retention, 174; strength 
 of, 190 ff.; and vividness, 299. 
 
 Associative recall, principle of, 
 187 ff. 
 
 Attention, 293 ff.; duration of, 
 313 ff., 318, 323 f.; and inter- 
 est, 301 f.; and motor adjust- 
 
 ment, 294, 296; scope of, 304 f.; 
 
 in voluntary recall, 193 f. 
 Audition, theories of, 81 ff., 123 ff., 
 
 143 f. 
 Auditory ossicles, 80. 
 Auditory sensations, physical 
 
 conditions of, 80 ff.; pitch of, 
 
 81 ff. 
 
 Beats, 30, 118 f. 
 
 Betweenness, 216, 218, 232. 
 
 Binocular rivalry, 223, 225 f. 
 
 Black, 67; sensational theory of, 
 60. 
 
 Blind-spot, 55. 
 
 Brain centres ; auditory, 80; as- 
 sociational, 195; of cutaneous 
 and sub-cutaneous sensation, 
 85 f.; gustatory, 45; of imag- 
 ination, 150; olfactory, 50; vis- 
 ual, 54. 
 
 Brain-paths, 194. 
 
 Brain processes, actual and ma- 
 terial, 21 f. 
 
 Character, personal, 289. 
 
 Characters of sensation, 32 ff. 
 
 Chiaro-oscuro, 223 f. 
 
 Chromopsia, 40. 
 
 Classification of sensation, 38 f. 
 
 Clay's theory of the specious pres- 
 ent, 308. 
 
 Clearness, 293. 
 
 Cochlea, 80 ff., 124. 
 
 Co-consciousness, 332 ff. 
 
 Cognition, 242. 
 
 Color adaptation, 74 ff. 
 
 Color blindness, see Achromop- 
 sia. 
 
 Color circle, 64. 
 
 Color contrast, 76 f. 
 
 Color mixing by rotating discs, 28. 
 
 Color onion, 65 f . 
 
 Color sensitivity of different por- 
 tions of retina, 74. 
 
 363 
 
364 
 
 INDEX 
 
 Color theories, 59 ft., 70 f., 73, 79. 
 
 Color triangle. 64. 
 
 Colors; complementary, 66; com- 
 posite, 57; elementary, 56 ff.; 
 fundamental, 57 f. 
 
 Conation, 243; and imagination, 
 250. 
 
 Conative feeling; and emotion, 
 264; spreading of, 253 ff. 
 
 Concept; and idea, 166 ff. ; in per- 
 ceived content, 197 ff.; devel- 
 opment of, 198 ff.; and judg- 
 ment, 303 ff. 
 
 Confusion, psycho-physiological, 
 20. 
 
 Consciousness, 6 f., 292 ff.; de- 
 grees of, 293 ff. ; kinds of. 292 f., 
 306; span of, 310; time rela- 
 tions of, 306 ff. 
 
 Conscious processes, 180, 184 ff. 
 
 Constant errors, 108 ff. 
 
 Content of consciousness, 7 ; com- 
 plexity of, 12; elements in, 13 ff.; 
 perceived, 196 ff. 
 
 Convergence and accommodation, 
 223, 225. 
 
 Corresponding points, 141 ff. 
 
 Cortical centres, 43. 
 
 Dark brown taste, 49, 99. 
 
 Deep sensibility, 93 f. 
 
 Deliberation, 271 f. 
 
 Depth perception, visual, 222 ff. 
 
 Descartes; fundamental formula, 
 336; theory of emotions, 259. 
 
 Desire, 242 ff., 250 ff . ; in volition, 
 269 ff. 
 
 Despair, 262. 
 
 Determination, 274. 
 
 Dichromopsia, 68. 
 
 Dionysius the Areopagite, influ- 
 ence of, 248 ff . 
 
 Direction, spatial, 216, 222 f. 
 
 Distance, spatial, 217. 
 
 Dizziness, 99. 
 
 Duration, 232 ff.; and algo-he- 
 donic tone, 246; and proten- 
 sity, 35, 120 f. 
 
 Ecstasy, 348. 
 
 Edge-contrast, 77. 
 
 Ego: the empirical, 285 ff.: the 
 real, 336 f.; functional theory 
 of, 337 ff.; not to be studied, 
 337, 339, 341; and will, 271. 
 
 Elements of content, classifica- 
 tion, of 13 ff. 
 
 Emotions, 243. 255 ff.; aesthetic 
 and religious, 257 ff.; classifi- 
 cation of, 263; and coensesthe- 
 sis, 259 ff . ; cognitive factors in, 
 261 ff.; and feelings, 15; mor- 
 bid, 256 f . ; and volition, 270. 
 
 Empiricism, 150. 
 
 Epicritic sensibility, 93 f. 
 
 Error, possibiUty of, 24. 
 
 Evil eye, the, 344. 
 
 Experience, 6; not complex, 12 f.; 
 and brain activity, 26 f. 
 
 Extensity, 34, 83 f.; auditory, 
 215, 216; differences in, 122 f.; 
 and extension, 122, 214 ff.; and 
 intensity, 134 ff.; physiologi- 
 cal basis, 123; and pitch, 123 ff., 
 215 f.; and space, 122. 
 
 Extensity theory of tone percep- 
 tion, 83, 123 ff. 
 
 Extension, 214 ff. 
 
 Fechner's colors, 79. 
 
 Fechner's formula, 114 f. 
 
 Fear, 260, 262. 
 
 Feeling, loose use of term, 243. 
 
 Feeling tone, 35. 
 
 Feelings, 243 ff.; as elements, 14 f,; 
 
 and \ividness, 298. 
 Fetichism, 252. 
 Fiat, 271. 
 
 Field of consciousness, 294. 
 Focus of consciousness, 295. 
 Fovea, 54. 
 Franklin, Mrs.; Color theory of, 
 
 62. 
 Fringe of consciousness, 295, 
 
 314 f. 
 Fusions, 183. 
 
 Galton's questionary, 153 f. 
 
 Gray sensations, 65 ff . 
 
 Groupings, rhythmic, 309 ff. 
 
 Gustation; physical and physio- 
 logical conditions of, 44 ff.; 
 confused with olfaction, 45 ff. 
 
 Gustatory papillae, 44, 48. 
 
 Habit, 281 ff.; and alteration of 
 
 personality, 334. 
 Hallucination, 203 ff. 
 Hedonic tone, 243; and conation, 
 
 250, 255 f . 
 
INDEX 
 
 365 
 
 Helmholtz; criterion of modality, 
 42 f.; theory of tone percep- 
 tion, 81, 84, 124, 143 f. 
 
 Hering's color theory, 60. 
 
 Huxley's theory of matter, 26. 
 
 Hypnotism, 268, 347. 
 
 Idealism, 23, 24, 25, 150, 228. 
 
 Ideas, 163 ff.; and algo-hedonic 
 feeling, 247 f.; and action, 
 267 ff.; and conative feeling, 
 251; and volition, 270 ff.; ab- 
 stract, 166. 
 
 Ideational reflex, 267 ff. 
 
 Illusion, 201 ft. 
 
 Illusions of reversible perspec- 
 tive, 319 ff. 
 
 Images, 14; and ideas, 163 ff., 
 167; as copies of sensations, 16; 
 spontaneity of, 177 f. 
 
 Imagination, 157 ff.; 306, 307; 
 creative, 161 ff.; function of, 
 160 ff . ; a kind of consciousness, 
 157; perceptional conditions 
 of, 169 ff.; physiological proc- 
 esses in, 155 f.; reproductive, 
 161; in science, 200; and 
 scientific training, 165 f . ; types 
 of, 154 ff. 
 
 Imitation, 279 f. 
 
 Instinct, 277 f. 
 
 Integration, principle of, 180 ff. 
 
 Intellect, 150 f. 
 
 Intellectual association, principle 
 of, 186 f. 
 
 Intensity of sensation, 33, 109 ff.; 
 and algo-hedonic feeling, 245 f . ; 
 and vividness, 295 ff. 
 
 Interactionism, 22, 25 ff. 
 
 Interest, 242; and apathy, 251; 
 and attention, 301 f.; spread- 
 ing of, 252 f.; and subjective 
 activity, 252. 
 
 Intermittence tones, 30. 
 
 Intuition, 16. 
 
 Irradiation, 135. 
 
 James-Lange theory of the emo- 
 tions, 259 ff. 
 Judgment, 303 f. 
 
 Knowledge, 7; mystical, 348 ff. 
 
 Learning; accidental, 278 f.; con- 
 ceptual, 280 f . ; imitative, 279 f . 
 
 Linnaeus' classification of odors, 
 52 f. 
 
 Local sign of sensation, 35, 137 ff. ; 
 and complexity of odors, 145; 
 differences in, 139 ff.; and ex- 
 tension, 139, 216, 222 f.; and 
 pitch, 143 ff.; and quality, 138. 
 
 Love, 262 f. 
 
 Margin of consciousness, 228, 295, 
 314 f. ; two sorts of, 328 ff. ; and 
 mind reading, 345. 
 
 Materialism, 25, 150, 228. 
 
 Matter; not experienced, 19; theo- 
 ries of, 26. 
 
 Mediumship, 350 ff.; natural, 
 353 f . ; supernatural, 350 ff. 
 
 Memory, 174 ff.; biological and 
 psychological, 174 f.; and 
 learning, 175 f.; and multiple 
 personaUty, 331 f.; and recog- 
 nition, 177; and plagiarism, 
 176 f. 
 
 Middle term, principle of, 185 f. 
 
 Mind: a multivocal term, 5; as 
 brain activity, 22; as objective 
 reality, 23. 
 
 Mind-reading, 345 ff. 
 
 Modality of sensation, 42 f. 
 
 Molecular weight and olfactory 
 sensation, 19, 53, 101. 
 
 Mood, emotional, 262. 
 
 Motive, 272 f . 
 
 Motor tendency of thought, 284. 
 
 Muscle sensation, 96 f. 
 
 Music and cognition, 258 f. 
 
 Musical ear, 144. 
 
 Mystic knowledge, 348 ff. 
 
 Nausea, 97. 
 
 Neo-Platonism, influence of, 
 
 348 ff. 
 Nervous process, ambiguity of 
 
 term, 20. 
 Neutral point, temperature, 88. 
 Nystagmus, 99. 
 
 Objects of consciousness, 7; ma- 
 terial, 19. 
 
 Occult, the, 342 ff.; and psy- 
 chology, 3. 
 
 Olfaction; physical conditions 
 of, 19, 50 f., 53, 101. 
 
 Olfactory region, 49 f . 
 
366 
 
 INDEX 
 
 Organic sensations, 97 f . 
 
 Osmic sensibility, variations in, 
 
 53 f. 
 Overtones, 125 ff. 
 
 Pain; as sensation, 86, 90 ff.; as 
 feeling, 242 ff. 
 
 Parachromopsia, 68 ff. ; detec- 
 tion of, 69. 
 
 Parallax, 223, 226. 
 
 Parallelism, 25. 
 
 Partials, tonal, 125 ff., 132 ff. 
 
 Pathos, 260. 
 
 Perception, 17; and the concept, 
 197 ff.; of things, 227 ff.; true 
 and false, 201 ff.; causes of 
 false, 208 ff. 
 
 Perceptual reflex, 267. 
 
 Personality, alternating, 291; 
 multiple, 331 ff. 
 
 Perspective; aerial, 223 f.; an- 
 gular, 223, 225; linear, 223, 
 224 f. 
 
 Photo-chromatic interval, 65. 
 
 Physics and psychology, 8 f., 11. 
 
 Physiological reflex, 265 ff. 
 
 Pitch of auditory sensation, 81 ff., 
 119, 123 ff., 134 f.; and exten- 
 sion, 124 f.; and intensity, 135. 
 
 Platonic Idea; and the concept, 
 166; and Matter, 150; and re- 
 lations, 149. 
 
 Pleasantness, 242. 
 
 Pleasure; as emotion, 262 f.; as 
 feeling, 242, 244 ff. 
 
 Present content, 17, 163. 
 
 Present moment ; actual and log- 
 ical, 240 f.; specious, 308 ff.; 
 logical, 308. 
 
 Process, psychological, 184, 273 f. 
 
 Protensities, comparison of, 121 f. 
 
 Protensity of sensation, 34, 120 ff. ; 
 and duration, 233. 
 
 Protopathic sensibility, 93 f . 
 
 Pseudo-mystical experience, 349. 
 
 Psyche, 2. 
 
 Psychic and psychical, 3. 
 
 Psychic research, 3, 342 ff. 
 
 Psychological analysis, problems 
 in, 185. 
 
 Psychological moment, 3. 
 
 Psychology, in popular usage, 3; 
 definition of, 4 ; preparation for 
 study of, 8; and the soul, 2, 341. 
 
 Psycho-physics, 114. 
 
 Psychotherapy, 351 f. 
 
 \l/vxokoyia, 2. 
 
 Qualities; cutaneous and sub- 
 cutaneous, 86 ff.; gustatory, 
 45; kinaesthetic and ccenaes- 
 thetic, 97 ff . ; olfactory, 52 f . ; 
 visual, 56 ff.; schematization 
 of, 62 ff. 
 
 Quality of sensation, 33; audi- 
 tory, 83 ff. 
 
 Rate, temporal, 232, 236 ff. 
 
 Recall, 177 ff.; and fading, 178; 
 spontaneous, 177 f.; volun- 
 tary, 192 ff. 
 
 Recognition, 175, 239. 
 
 Redintegration, principle of, 
 187 ff. 
 
 Reflexes, 265 ff. 
 
 Reinstatement, principle of, 
 187 ff. 
 
 Relations; in association, 186 f. ; 
 directly experienced, 14, 146 f, 
 151; elementary and complex, 
 148 f.; in emotions, 262; and 
 fusions, 183 f.; imagined, 
 165 ff., 222; and logic,151 f.; 
 motor theory of, 151; neural 
 conditions of, 147 f.; and Pla- 
 tonic Ideas, 149 f.; spatial, 
 214 ff., 222; temporal, 230; and 
 vividness, 300 f., 305; in vol- 
 untary recall, 194. 
 
 Relative strength, principle of, 
 190 ff. 
 
 Relativity of sensation, 110 f., 
 116 f. 
 
 Repugnance, 242 ff., 250 ff., 269 ff. 
 
 Retention, 170 ff . ; conditions of, 
 172 ff.; effective without re- 
 call, 174; individual variations 
 in, 171 f.; and recall, 177; and 
 the subconscious, 327, 329. 
 
 Retinal rivalry, 319. 
 
 Retinal streaming, 78 f. 
 
 Rhyme and association, 189. 
 
 Rhythm, 308 ff . ; and association, 
 189. 
 
 Rods and cones, 54. 
 
 Saturation, chromatic, 63. 
 
 Scale; chromatic, 130 f.; dia- 
 tonic, 125 ff., 128 ff.; equally 
 tempered, 131. 
 
INDEX 
 
 367 
 
 Scales, primitive, 129, 130, 131. 
 
 Secondary phase of sensation, 
 306 ff. 
 
 Self, the empirical, 285 ff.; di- 
 vided, 289 ff.; function of, 
 288 ff. 
 
 Sensation, 14, 43 f.; and algo- 
 hedonic tone 244, 250; charac- 
 ters of, 32 ff. ; and image, 306 f., 
 317; lag of, 27 ff.; localiza- 
 tion of, 137 ff.; location of, 23 
 ff.; and nervous process, 20 ff., 
 25; and stimulus, 18 ff., 27 ff., 
 109 ff.; two phases of, 306 f. 
 
 Sensation-continuum, 42 f.; vi- 
 sual, 56, 57 ff. 
 
 Sensational reflex, 266 f. 
 
 Sensations: of ache, 91, 100: al- 
 getic, 86, 90 f . : auditory, 81 ff. ; 
 physical conditions of, 102 f.: 
 classification of, 38 f . : coenses- 
 thetic, 95, 97 ff.; and emotion, 
 259 f.: cutaneous and sub-cu- 
 taneous, 86 ff . ; dissociations of, 
 
 94 f.; end organs of, 84 f., 94; 
 topography of, 92 f.: of effort, 
 97: gustatory, 44 ff. ; physical 
 conditions of, 103: of heat, 90, 
 93: of itch, 91: kinaesthetic, 
 
 95 ff . : olfactory, 49 ff . ; physical 
 conditions of, 53, 101, 103.: of 
 pressure, 87 f., 94: secondary, 
 31 f.: subjective, 156: tactual, 
 86 f., 92 f. : terminology of, 39, 
 42: titillatory, 87, 93 f.: tricho- 
 aesthetic, 39, 93; visual, 56 ff. ; 
 physical conditions of, 101, 
 103: of warmth and cold, 88 ff. 
 
 Sense organs, 40 ff. 
 
 Senses, 38 ff. 
 
 Soul, 2, 341; a multivocal term, 
 5. 
 
 Sound wave a continuous stimu- 
 lus, 31. 
 
 Space; and auditory perception, 
 226 f.; and local sign, 122, 139; 
 mathematical, 212; and mus- 
 cular sensation, 218; three di- 
 mensional, 220, 223 ff.; two 
 dimensional, 217, 219. 
 
 Space perception, theories oJ, 
 212 f. 
 
 Space relations, 213 f., 222. 
 
 Spaces, co-ordination of, 218 ff. 
 
 Span of consciousness, 310. 
 
 Spectrum, chromatic, 56. 
 
 Spinoza's theory of emotion, 259. 
 
 Spinozistic monism, 339. 
 
 Spirits, 353. 
 
 Spiritualism, 350 ff. 
 
 Stimulation, intermittent, 28 ff. 
 
 Subconscious, the, 325 ff. ; and 
 hypnotism, 328; misuse of con- 
 cept of, 173, 326 ff. 
 
 Talbot-Plateau law, 29. 
 
 Taste buds, 42 ff. 
 
 Telepathy, 343. 
 
 Telephone theory of tone percep- 
 tion, the, 82. 
 
 Temperature-zero, 89. 
 
 Temporal extent, 232 f.; meas- 
 urement of, 233 f.; direct es- 
 timation of, 235 ff. 
 
 Te^minolog5^ principles in, 5. 
 
 Things, metaphysical, 229; per- 
 ceived, 227 ff. 
 
 Three color theory, 59 ff. 
 
 Thresholds, 101 ff ; difference, 105, 
 114 f.; stimulus, 101 ff.; two 
 point, 139 ff., 217. 
 
 Timbre, 83 f., 132 ff.; schematic 
 representation of, 133. 
 
 Time; metaphysical, 231, 239; 
 passing, 230 ff . ; past and pres- 
 ent, 238; and protensity, 121; 
 and retention, 172 ff. 
 
 Time order and recall, 189 f. 
 
 Time perception, theories of, 
 229. 
 
 Tone: affective, 242 ff.; and neu- 
 ral process, 245: algo-hedonic, 
 35, 243 ff.; and intensity of 
 sensation, schematized, 245 f. ; 
 and sensation duration, 246; 
 and imagination, 247 f.; and 
 repetition, 247; conditions of, 
 248 ff . : emotional, 243. 
 
 Tone intervals, 130. 
 
 Traces, mental, 170 f. 
 
 Transcendental unity of apper- 
 ception, 339. 
 
 Vedantist theory of the world, 23, 
 
 24, 25. 
 Vision, single and double, 141 ff. 
 Visual acuity, 55. 
 Vividness, 293 ff.; and efficiency 
 
 of thought, 302 f.; factors de- 
 
33 
 
 / 
 
 368 
 
 INDEX 
 
 termining, 298 ff . ; fluctuations 
 in, 316, 318 ff. ; and habituation, 
 314 f.; and intensity, 295 ff.; 
 lower limit of, 325 f. 
 Volition, 270 ff.; as activity, 
 273 f. 
 
 7. */Sr7y3 . 
 
 Wind instruments and the dia- 
 tonic scale, 127. 
 Wish, 274. 
 
 Young-Helmholtz color theory, 
 the, 59 f., 70 f., 73, 79. 
 
 Weber's law. 111 ff. 
 White, 67. 
 
 Zwaardemaker's classification of 
 odors, 52 f. 
 
Deacidified using the Bookkeeper pro( 
 Neutralizing agent: Magnesium Oxide 
 Treatment Date: Oct. 2004 
 
 PreservationTechnologi 
 
 A WORLD LEADER IN PAPER PRESERVA 
 
 1 1 1 Thomson Park Drive 
 Cranberry Township, PA 16066 
 

 
 ■»•'?,-!' 
 
 ':\:^,'^ 'V 
 
 
 LIBRARY OF CONGRESS 
 
 013 310 258 9