CORNELL UNIVERSITY LIBRARY BOUGHT WITH THE INCOME OF THE SAGE ENDOWMENT FUND GIVEN IN 1891 BY HENRY WILLIAMS SAGE Cornell University Library arV13S68 Psychological experiments 3 1924 031 239 365 olin.anx Cornell University Library The original of tliis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924031239365 PSYCHOLOGICAL EXPERIMENTS J. V. BREITWIESER, A. M., Ph. D. Professor of Psychology and Education, Colorado College Published by the APEX BOOK COMPANY Colorado Springs, Colo. 1914 f\ /\.^.Sv)-?(,c> COPYRIGHT, 1914 Sy the APEX BOOK COMPANY Published, January, 1914 tICo Mp WiiU Psychological EKperiments Contents Sm.^Il numbers refer to the number of the experiment. T> f Page Preface 1 CHAPTER 1. Instructions to Students 5 CHAPTER 2. Statistical Methods H The Mode— Average— Median— Mean Variation— Standard Deviation— Probable Error— Curves and Diagrams— Illustrative Tables. CHAPTER 3. Structure of the Nervous System 23 The Skull, 1 — Spinal Column, 2 — Comparative Study of Brains, 3 — Brain, 4 — Spinal Cord, 5. CHAPTER 4. Cutaneous Sensations 33 Cold Spots, 6 — Hot Spots, 7 — Touch or Pressure Spots, 8^ — Pain Spots, 9 — Charting Pain Spots, 10 — Temperature Adapta- tion, 11 — Temperature After Images, 12 — Application of Touch, Prick and Electrical Stimulations on Cold and Hot Spots, 13 — Pressure Experiment, 14 — Pain and Touch Experiment, 14— Pain and Touch Spots, 15 — Pain Endings Inside the Cheek, 16 — Pain and Temperature Sense, 17 — Relation of Extent to Intensity of Thermal Sensation, 18 — Pain Threshold, 19 — Touch Discrimina- tion of Tw^o Points, 20 — Discrimination of a Point from a Line, 21 — Apparent Distances on the Cheek, 22 — Judgment of Distance Around the Lips, 23 — Arisotle's Illusion, 24 — Absolute Touch Localization, 25. PSYCHOLOGICAL EXPERIMENTS {Contents continued) CHAPTER 5. Gustatory Sensations 49 Nature of Substance Tasted, 26— Gustatory Acuity, 27— Re- actions of Individual Taste Papillae, 28— Weak Taste, 29— Effect of Cocaine on the Taste Papillte, 30— Detection of Various Tastes, 31— Simultaneous Taste Contrast, 32— Successive Taste Contrast, 33. CHAPTER 6. Olfactory Sensations 55 Olfactory Acuity, 34 — Classification of Odors, 35- Olfactory Fatigue, 36r-Odor Mixing, 37. CHAPTER 7. Labarynthine Sensations 59 Labarynthine Sensations and Movement, 38 — Labarynthine Sensations and Eye Movement, 39 — Sense of Vertical Position, 40. CHAPTER 8. Auditory Sensations 63 Auditory Acuity, 41 — Auditory Adaptation, 42 — Sound Con- duction, 43 — Nature of Resonance, 44— -Aural Resonance, 45 — Ear as a Resonator, 46 — Measuring Wave Length by Resonance, 47 — Nature of Overtones, 48 — Timbre, 49 — Discrimination of Pitch, 50 — Tone Character, 51 — Intensity of Tones, 52 — Upper Limit of Pitch, 53^Lower Limit of Pitch, 54 — Auditory After Sensations, 55 — Beats, 56. CHAPTER 9. Visual Sensations 75 Pirkinje's Images, 57 — The Blind Spot, 58 — Visual Adapta- tion, 59 — Visual Acuity, 60 — Discrimination of Brightness, 61 — Visual Difference Threshold, 62 — Test for Color Blindness, 63 — To Find Original Colors by Means of Peripheral Vision, 64 — Charting the Color Areas of the Retina, 65 — Effect of Distance on Apparent Brightness, 66 — Brightness and Intensity, 67 — Per- ception of Colors, 68— Positive After Image, 69 — Tints, 70 — Shades, 71 — Mixing Various Colors not Complimentary, 72-— Mix- ing Blue and Yellow to Produce Neutral Grey, 73 — Mixing Red PSYCHOLOGICAL EXPERIMENTS (Contents continued) and Green to Produce Neutral Grey, 74 — Mixing More Than Two Colors to Produce a Neutral Grey, 75 — Color Contrast, 76 — . Brightness and Contrast Color, 77 — Brightness Contrast, 78 — Contrast Color in Shadow, 79 — Negative After Image, 80 — Effect of Time of Fixation on the After Image, 81 — Effect of the Stimulus Field on the After Image, 82 — Effect of the Back- ground Field on the After Image, 83. CHAPTER 10. Movement 101 Tapping Test, 84 — Detection of Passive Movements, 85 — Right and Left Handedness, 86 — Sense of Movement, 87 — Feel- ing of Resistance, 88 — Steadiness Test, 89 — Steadiness and Ac- curacy, 90 — Judgment of Weight, 91 — Judgment of Weight with an AncCsthetic Skin, 92 — Size Weight Illusion, 93 — Fatigue, In- termittent Contraction, 94 — Fatigue, Constant Contraction, 95 — Rest, 96 — Practice, 97 — Learning New Motor Coordinations, 98. CHAPTER 11. Perception Ill Reversible Figures, 99 — Measuring Amount of Illusion, 100^ Puzzle Pictures, 101 — Stereoscope, 102 — Sterescope, 103 — Other Forms of Stereoscopic Vision, 104^General Stereoscopic Slides, 105 — The Exposure Apparatus, 106 — Perception of Irregular Forms, 107 — Perception of Regular Forms, 108 — Perception and Reproduction, 109 — Perception of Lines, 110 — Perception of Various Forms of Material, 111— Speed of Reading, 112— Visual Span in Reading, 113 — Correlation of Visual Span in Various Forms of Material, 114 — Visual Span for Different Kinds of Printed Matter, 115 — Perception of Letters, .116 — Illusions of Direction, 117— Illusions of Extent, 118. CHAPTER 12. Attention 129 Masson Disc Experiment, 119— Attention in Hearing, 120. CHAPTER 13. Perception of Time 133 Rhythm and Time Sense, 121— Rhythm and Time, 122— Sub- jective Rhythm, 123— Objective Rhythm, 124. PSYCHOLOGICAL EXPERIMENTS (Contents continued) CHAPTER 14. Reaction Time Experiments 137 Natural Auditory Reaction Time, 125 — Auditory Sensory Re- action Time, 126— Auditory Motor Reaction Time, 127 — Visual Natural Reactions, 128 — Visual Sensory Reactions, 129 — Visual Motor Reactions, 130 — Tactual Reactions, Normal, 131 — Tactual Sensory Reactions, 132 — Tactual Motor Reactions, 133 — Dis- crimination Time, 134 — Discrimination Time, 135 — Recognition Time, 136 — Free Association Time, 137 — Controlled Associations, 138 — Judgment Time, 139 — Attention Fluctuations, 140 — Intensity of Stimulus and Reaction Time, Auditory, 141 — Intensity of Stimulus and Reaction Time, Visual, 142 — Intensity of Stimulus and Reaction Time,- Tactual, 143. CHAPTER 15. Judgment 151 Weber's Law for Lifted Weights, 144 — Weber's Law for the Felt Length of Lines, 145 — Judgment of Distance. 146. CHAPTER 16. Imagination and Intelligence. 155 Mental Imagery, 147— Illusory Warmth, 148— Completion or Filling in Tests, 149 — Imagination and Invention, 150 — Vocabulary Test, 151. CHAPTER 17. Memory 163 Economy in Memorizing, 152— Measurement of Memory, 153 —Memory of Auditory Images, 154 — Memory for Various Forms of Images, 155— Memory for Various Forms of Images, 156 — Memory of Visual Images, 157 — Memory of a Series, 158 Fidelity of Report, 159— Fidelity of Report of an Incident,, 160. CHAPTER 18. Affective Consciousness 173 Mental Analysis by the Association Time Method, 161— Affective Consciousness, Comparative Method, 162 Affective Consciousness, Order of Merit Method, 163— Aesthetic Division PSYCHOLOGICAL EXPERIME NTS (Contents continued) of a Line, 164 — Pneumograph Records, 165 — Plethysmographic Records, 166 — Feeling and Unconscious Movement, 167 — Elec- trical Conductivity of the Body, 168. List of Materials 183 PREFACE Psychology is now largely taught with con- stant reference to experimental data. The liter- ature that contains the experiments is so scat- tered and profuse that it is not readily accessible to the beginning student. In presenting this list of experiments it has been my aim to offer a series that will supple- ment the work usually given in connection with courses in the elements of general psychology. Enough work is outlined to keep the students busy for a full school-year in the laboratory. Again, selections can be made for brief courses or for private inquiry. An attempt has been made to avoid the ne- cessity of using special or peculiar forms of ap- paratus. The problems and" general procedures are given to be worked out in the best possible manner with the materials that can be obtained. The experiments are given first, the list of materials and apparatus following, so the reader really gets the aim and method of procedure of the exercise in mind before starting mechanic- ally to gather his apparatus. 2 PSYCHOLOGICAL EXPERIMENTS I have excluded all names of experimental psychologists, valuable as they are, and all data or reports of experiments. This little book is intended for students who are seeking psychological knowledge at first hand. I hope sufficient details have been given to prove useful to the thinking student. Blank spaces have been left upon which to record references, special supplemental instruc- tions, important results, etc. A brief chapter on statistical methods has been presented for the purpose of enabling the student to utilize his results to the best advan- tage. A careful study of the data from the sta- tistical point of view will often help the experi- menter to get more out of his work. Seven years experience with laboratory stu- dents and in courses dealing with students in beginning psychology has led me to believe that a book of the most important experiments, with- out too much detail, that can be used along with any good text, would fill a long felt want. The experiments have been gathered from the works of many authors. My chief sources have been, Titchener, Myers, Seashore, Witmer PREFACE 3 and Sanford. Many others have contributed something and when they find that I have used some of their material they will know that they have rendered me a great service and that this statement is a grateful acknowledgment. I have received many valuable suggestions from my former teachers, Professors, J. A. Bergstrom, E. H. Lindley, R. S. Woodworth and James McK. Cattell. My brother, T. J. Breit- wieser, has kindly read the manuscript and proof which proved to be an invaluable aid in the preparation of this book. Many errors will doubtless appear for which my friends are not to blame. Their friendly criticism may enable me to do something better in the future. PSYCHOLOGICAL EXPERIMENTS CHAPTER 1. Instructions to Students A psychological experiment fixes certain standard conditions under which consciousness is to be studied. The value of the. conclusions will depend largely on the introspections made during the experimental period. Introspection is the fundamental psycholog- ical method. Every experimenter is conscious, therefore since psychology is the science of con- sciousness, he carries the object of inquiry with him, convenient for constant examinations. The experiment places the subject under the condi- tion desired for the introspective report. An ac- curate report of the external conditions is also necessary. Most psychological experiments require two persons for their performance; the experi- menter who manipulates the apparatus and. re- cords the results; the subject or observer is the one who is put under the experimental condi- tions and makes the introspections. All ex- periments should be performed twice so that the experimenter and subject can change places and each have records. Read the instructions carefully so as to get the problem clearly in mind. Do not set up the apparatus until you know what you want to do with it. When you have the problem clearly in mind gather your materials and apparatus, and 6 PSYCHOLOGICAL EXPERIMENTS see that everything is in good working condi- tion. Remember that you are trying to analyze a bit of the subject's consciousness and in no case try to make records. Maintain the same method throughout the same series of experiments. Do not modify your procedure unless there is ample justifica- tion. The records made previous to the change will likely prove valueless. Maintain a uniform attitude toward the subject unless the experi- ment calls for something else. Do not try stunts or tricks for they will vitiate all results. Do not continually ask what the results should be, you have the means by which you can find out. Do not continually annoy other experimenters by asking them for their results. Comparisons are valuable only if properly done. It is more val- uable to read the reports of carefully made ex- periments of psychologists. Do not become dis- couraged because your results are not accurate. They will likely demonstrate the method and give you many interesting facts first hand. Al- ways refine your methods as much as possible and strive for the greatest accuracy, under the given circumstances. This will give you splen- did scientific training. Learn to overcome minor difficulties your- self, but do not alter everything or change ap- paratus that is doing the work merely because you think you know more about it than' your instructor. If accidentally or through carelessness you have injured some piece of apparatus report it INSTRUCTIONS TO STUDENTS 7 promptly, you will thus save time and help the efficiency of the laboratory organization. Lab- oratory partnerships should be continued throughout the year. It is therefore desirable that congenial partners be chosen as well as some one who can arrange their work so as to meet at times most convenient to both parties. Proper consideration for your partner will cause you to be punctual, considerate, alert and truthful. Should you be unable to keep your laboratory appointment, notify your instructor and your partner. Cooperate in every way to- ward the accomplishment of the highest grade of experimental work and there need be no doubt but that you will be amply repaid for all honest effort. Records Students will need two sets of note books or note-sheets. A daily note book into which to enter the results, introspections, remarks, etc. quickly while the experiments and discussions are under way. As soon as possible the experi- ments should be worked up and recorded in permanent form. Every experiment should show: — 1. The problem, aim, purpose or question of the experiment. 2. A description of the apparatus and method of procedure. Diagrams, pictures and drawings are very valuable, in describing the apparatus. 3. The results of the experiment in the form of tables, charts, descriptions, etc. PSYCHOLOGICAL EXPERIMENTS 4. A discussion of the results with the con- clusions they warrant. 5. The application of the results in life, education, hygiene, etc; also remarks on spe- cial points, extracts from references that have a bearing on the same problem, comparisons with members of the class with reasons for agree- ment, disagreement and other conclusions. If you have a new explanation to offer do so, if it really seems to you that you have facts to warrant it. The instructor should put you right it you have gone astray. It is better to offer something, even though wrong, than to do no thinking at all. Have your note book checked up by the in- structor. Revise parts that are not up to stand- ard. Turn your note book in for revision with the idea of being helped rather than that of expecting mere praise or condemnation. Read psychological discussions in texts and journals relating to the subject of your experi- ments. In the light of your data and facts gleaned from other sources offer the best dis- cussion possible. Go at the work in a true stu- dent attitude and experimental psychology will doubtless prove to be an interesting and profit- able study. NOTES 10 PSYCHOLOGICAL EXPERIMENTS CHAPTER 2. Statistical Methods This chapter is not intended as a discussion of statistical methods but the aim is to present the formulae and methods that are needed in every general course in Psychological Experi- mentation. For a fuller discussion the student is re- ferred to Thorndike, Mental and Social Meas- urements; Whipple, Manual of Mental and Physical Tests, Ch. Ill; Davenport, Statistical Methods and many others vi^ho have worked out methods that apply to special groups of meas- urements. In psychology a single experiment is usually not enough to warrant a conclusion. It is im- possible to keep in mind all of an extended series of measurements. Often a series of results are unintelligible until they have been systematized by the proper statistical method. Statistical treatment is especially necessary in an attempt to condense a long series of measurements, to summarize their tendency or direction. The Mode The mode of a series of measurements is the value of that 'measurement which appears the greatest number of times. A group of measure- ments may have more than one mode, in this event a more accurate definition of a mode 12 PSYCHOLOGICAL EXPERIMENTS would be, that a mode is a measure that appears more frequently than the measure above or be- low it in an ascending or descending order of values. One way to' find a mode is to actually list the number of cases that fall within the range of each measurement, the measurements being taken up in regular ascending or descending order. The modes can be located directly from this data. For the students in experimental psychology it is good practice to plot a curve that shows the distribution of the measurements graphically. When the measurements are so accurate or so distributed that they do not fall into groups, the measurements can be divided into 5, 6, 7, 8, etc., ranges of values and all cases counted in one group that fall within the range of those values. The higher points on the curves of distribution are the modes. Average The arithmetical mean or average is found by dividing the sum of the measurements by their number. . Sum of mea surements Number of measurements or Av.^ n Av. is average. — is sum of. STATISTICAL METHODS 13 m is measurements or magnitude, n is the number of cases from which the record were used. It is evident that each measure must be ac- curately recorded and that for a large number of measurements it requires much labor to find the average. Where a large number of measurements are to be dealt with a weighted average, or weighted arithmetical mean will often suffice. This value is found by dividing the whole range of measurements into a limited number of groups and recording the number of cases that fall within that group. The weighted average can then be found by multiplying the measure of each group by the number of cases found in that group and dividing the sum of the products by the total number of cases or measurements represented. Av.- ^ Av„ is weighted average f is the frequency or number of cases in each group. Median The median or central value represents that measurement above and below which an equal number of cases lie when the whole series has been arranged in an ascending or descending 16 PSYCHOLOGI CAL EXPERIMENTS The above is for an individual case in the series. The reliability of an average can be indi- cated by the P. E. of av. which is found by mul- tiplying the standard deviation by 0.6745 and dividing the product by the square root of the number of measurements or cases. O. 6745S. D. r. L. av. = in Curves and Diagrams Many psychological traits vary or distribute themselves within certain limits. A list or state- ment of the frequencies of each measurement is valuable but the facts can often be made more vivid by means of a visual presentation. It is good practice whenever possible to represent the results graphically. One of the simplest types of curves is repre- sented in the time needed for the performance of a given task, for the first trial, and after hav- ing repeated the performance. The repetitions can be located at regular in- tervals along a line and the time can be located by a point directly above the point on the base line representing that trial. The distance above the line should be directly proportional to the time. A point above the line should thus be located for each trial or the average for each group of trials. Connecting the points by means of straight lines, a graphic representa- STATISTICAL METHODS 17 tion of the increase or decrease of time con- sumed will be obtained. This method can be used whenever two fac- tors enter into the record. Groups of variables Often appear where the mere distribution of cases is important regardless of the order in which they came. These can be shown by having various ranges of values, or quantities represented along a base line and erecting above each division a column proportional to the num- ber of cases that fall within the range of the values or quantities of that division. Such a curve will appear as a series of rectangles stand- ing along side each other. Sometimes the dis- tribution comes out more clearly by joining the mid-points of each of the columns. The number of groups represented on the base line and the distance by which each case is to be represented depends on the nature of the data and the purpose for which the graph is made. Tables Illustrating the Use of the Above Form- ulae Column (1) is the list of letters representing mdividuals. Column (2) is a series of measure- ments for the individuals. Column (3) repre- sents the individual deviations from the aver- age. Column (4) gives the squares for the deviations for finding S. D. The measurements are arranged in their ascending order for find- ing the median in column (5). 16 PSYCHOLOGICAL EXPERIMENTS The above is for an individual case in the series. The reliability of an average can be indi- cated by the P. E. of av. which is found by mul- tiplying the standard deviation by 0.6745 and dividing the product by the square root of the number of measurements or cases. O. 6745 S. D. P. E. av.= , — in Curves and Diagrams Many psychological traits vary or distribute themselves within certain limits. A list or state- ment of the frequencies of each measurement is valuable but the facts can often be made more vivid by means of a visual presentation. It is good practice whenever possible to represent the results graphically. One of the simplest types of curves is repre- sented in the time needed for the performance of a given task, for the first trial, and after hav- ing repeated the performance. The repetitions can be located at regular in- tervals along a line and the time can be located by a point directly above the point on the base line representing that trial. The distance above the line should be directly proportional to the time. A point above the line should thus be located for each trial or the average for each group of trials. Connecting the points by means of straight lines, a graphic representa- STATISTICAL METHODS 17 tion of the increase or decrease of time con- sumed will be obtained. This method can be used whenever two fac- tors enter into the record. Groups of variables orten appear where the mere distribution of cases is important regardless of the order in which they came. These can be shown by having various ranges of values, or quantities represented along a base line and erecting above each division a column proportional to the num- ber of cases that fall within the range of the values or quantities of that division. Such a curve will appear as a series of rectangles stand- ing along side each other. Sometimes the dis- tribution comes out more clearly by joining the mid-points of each of the columns. The number of groups represented on the base line and the distance by which each case is to be represented depends on the nature of the data and the purpose for which the graph is made. Tables Illustrating the Use of the Above Form- ulae Column (1) is the list of letters representing mdividuals. Column (2) is a series of measure- ments for the individuals. Column (3) repre- sents the individual deviations from the aver- age. Column (4) gives the squares for the deviations for finding S. D. The measurements are arranged in their ascending order for find- ing the median in column (5). 18 PSYCHOLOGICAL EXPERIMENTS TABLE 1 (I) (2) (3) (4) (5) A. 27 3 9 26 B. 26 4 16 26 C. 30 26 D. 26 4 16 26 E. 27 3 9 27 F. 27 3 9 27 G. 26 4 16 27 H. 28 2 4 27 I. 36 6 36 28 J. 26 4 16 30 K. 36 6 36 36 L. 27 3 9 36 M. 36 6 36 36 N. 36 6 36 36 0. 36 6 36 36 15)450 15)60 15| 284 27 Mn av. 30 m.v. 4 18.93(S.D.)2 4.34 S.D. STATISTICAL METHODS !<) Table II presents another series of measure- ments for the same subjects as table I. The cal- culations are given in the same order. These two tables, I and II, form the basis for the calcula- tion of the coefficient of correlation, table III. TABLE II A. 12 13 169 10 B. 11 14 196 11 C. 25 12 D. 14 11 •121 14 E. 17 8 64 17 F. 22 3 9 19 G. 19 6 36 22 H. 31 6 36 25 I. 33 8 64 28 J. 38 13 169 31 K. 40 15 225 33 L. 10 15 225 36 M. 28 3 9 38 N. 36 11 121 39 0. 39 14 196 40 15)375 15)140 15) 1640 25 Mn av. 25 m.v. 9.33 109.33 (S.D.)2 4.34 S.D. 20 PSYCHOLOGICAL EXPERIMENTS TABLE III X Y X Y series series deviations deviations XY A 27 12 -3 -13 +39 B 26 11 -4 -14 +56 C 30 25 D 26 14 -4 -11 +44 E 27 17 -3 -8 +24 F 27 22 -3 -3 +9 G 26 19 -4 -6 +36 H 28 31 -2 +6 -12 I 36 33 +6 +8 +48 J 26 38 -4 + 13 -52 K 36 40 +6 + 15 +90 L 27 10 -3 -15 +45 M 36 28 +6 +3 + 18 N 36 36 +6 + 11 +66 36 39 +6 + 14 i(xy)= +84 =495 ^(xy) 495 _ -=0.72 + T n(S.D.)x ■ (S.D.)y ~r5/4y5xl0.45 ""' r = coefficient of corre ;lation. xy = = product of the X deviations times the y de- viations. (S.D.)x=the standard deviations of the x series. (Table 1) (S.D.)y— the standard deviations of the y series. (Table 2) NOTES 21 22 PSYCHOLOGICAL EXPERIMENTS CHAPTER 3. Structure of the Nervous System Number l. The Skull The head of a sheep, cat, dog or rabbit can easily be obtained. The skull can be prepared for examination as follows : — Divide the skull into halves lengthways, using a saw, chisel and sharp knife. Boil the head until the flesh be- comes soft enough to be easily scraped from the bones. Soak the bones in lime water then ex- pose them to the sun; this will bleach them. If care is taken early enough in the boiling pro- cess the bones of the ear can be saved. Examine the prepared skull, locating every- thing that appears in black. Note the dome like brain cavity and by means of a human skull or pictures compare the size and shape of the brain-cavity of an animal with that of a human being. Note the position of the eye socket or optic' orbit. Toward the back of this orbit will be found an opening, the optic foramen, which serves for the passage of the optic nerves and the opthalmic artery. Near the nasal margin another small opening can be found. Through this the tears flow into the nose. This opening which serves as a passage for the lachrymal duct, is known as the lachrymal canal. Toward the back end of the skull (in the lower animals) a projecting bone is evident. In this temporal bone can be located the auditory 24 PSYCHOLOGICAL EXPERIMENTS canal and its connection with the nose through the Eustachian tubes. Inside this canal in the bottle shaped bone is where the three small bones, malleus, incus and stapes, were sus- pended. By careful sectioning of the temporal bone the relative position of the labyrinth or the internal ear cavity can be ascertained with os- soeus canals for the semi-circular canals and the cochlea. Forming the roof of the mouth cavity is the hard palate. Above the hard palate lies the nasal cavity which is roofed by the nasal bones. The lower rear end of the nasal cavity opens into the throat. By means of drawings and references to cuts make out as many parts of the skull as possible. This will give an idea of the relative positions of the sense organs. Often the open- ings for all the larger nerves can be made out. If the laboratory has some human skulls a more detailed study is useful. Get the names and positions of the various parts from any good textbook on anatomy. A knowledge of the skull and the anatomy of the nervous system are essential in any attempt to understand modern psychology. Materials — A head or skull of some lower animal, such as as that of a dog, sheep or ox, (human skull). 2. Spinal Column Examine a prepared speciman of the spinal STRUCTURE OF THE NERVOUS SYSTEM 25 column. It consists of a series of bones called vertebrae. The vertebrae are connected by means of articular or joint process and the inter- vertebral cartilages. The large solid part of an individual vertebrae is called the body. In it will be fond the openings for various nutrient vessels. The pedicles project backward, one on each side from the upper part, of the body. Just back of the body above and below the pedicles are the intervertebral notches, two on each side which in conjunction with the notches above and below form the intervertebral foramina. These foramina transmit the spinal nerves and blood vessels. Two broad, flat bones complete the vertebral arch and close the spinal canal. These plates of bone are called Laminae. Four Artcular Processes project from the junction of the pedicles and laminae. A long process that projects backwards and serves for the attach- ment of the muscles is known as the transverse process, one on each side projects from the point where the articular processes join the pedicle. The vertebrae, thirty-three (human) in number, have been divided and named as follows: The first seven after leaving the skull, cervical; the next twelve dorsal; then five lumbar; five sacral and four coccygeal vertebrae. The bones of the sacral and the coccygeal region become so firm- ly united in the adult human that the separate vertebrae cannot be distinguished. Consult any good anatomy. 26 PSYCHOLOGICAL EXPERIMENTS Materials — A prepared specimen of the spinal column. 3. Comparative Study of Brains Carefully dissect out the brain of a fish, frog, chicken, sheep, cat or other animals represent- ing various scales of intelligence. Harden the brains by placing them in a lO'A formalin solu- tion. Make drawings of the mesial sections of the brains and note the relative sizes of the cere- brum, cerebellum and the bulb. Materials — Heads of a fish, frog, chicken, sheep, cat or other animals, a dissecting set. 4. Brain By cutting around a fresh skull in the shape of a cap, the top can be lifted off for an exam- ination of the brain. Care must be taken not to saw too deep, it being best to pry off the top when most of the bone has been sawed through. The tough membrane which lies next to the boney wall of the brain cavity is the Dura Mater. The brain is divided into two hemi- spheres by the falx cerebri, a fold of the Dura Mater, dropping down like a crescent shaped curtain. An arched curtain, the tentorium cerebelli, covers over the lower division of the brain which in turn is divided into hemispheres by the falx cerebelli. Beneath the Dura Mater lies the delicate Arachnoid membrane. It is filled with the cerebro-spinal fluid. A thin vas- STRUCTURE OF THE NERVOUS SYSTEM 27 cular membrane, the Pia Mater, with a net work of arteries and veins held together with con- nective tissue, follows the convolutions of the brain and cord. After having removed the skull-cap lift the front of the brain out slowly and carefully cutting it loose whenever neces- sary, or cutting the bone away by means of nip- pers. Work back slowly and by the help of charts and pictures locate the parts as you come to them. The olfactory lobes lie in grooves in the base of the cranial cavity and will be torn off if the branches that go through to the nose cavity are not cut from them. The two large branches of the optic nerve will then be encoun- tered joining in an x shape forming the optic chiasma. In a little cavity lying on the floor of the cranial box will be the pituitary body joined to the main part of the brain by the infundi- bulum. The pituitary body will probably have to be left in its cavity. Just behind the infundi- bulum will be seen the double small round pro- jecting mamillary body. Just back of these lie the roots of the third cranial nerves. (The first was cut at the olfactory lobes, the second was the optic). Turning to the right and left in a forward direction are the large fibrous masses forming the roots of the right and left hemi- spheres of the cerebrum called the peduncles. The student will now have reached the portion of the brain where it follows the cavity into a. rather sharp downward turn. The pons forms a broad connecting band between the two sides. Out of the pons riise the double roots of the 28 PSYCHOLOGICAL EXPERIMENTS fifth cranial nerve. At the back of the pons and just in front of the enlarged bulb formation, the medulla- oblongata, lie the roots of the sixth, seventh and eighth cranial nerves in the above order from the center outward. The head of the bulb presents two slender triangular bodies running lengthwise called the pyramids. The olivary bodies lie on either side and above the pyramids. The roots of the tenth and twelfth cranial nerves rise out of the upper portion of the olivary body while the double branched roots of the eleventh nerve rise between the pyramids and the olive. Looking down from above the deep longitudinal fissure presents itself dividing the cerebrum into a right and left hemispheres. Draw the hemispheres apart and they will be found held together by a band of brilliant white fibrous tissue, the corpus cal- lusum. Pull the cerebellum, the large double lobed part of the brain lying back under the cerebrum, forward separating it above. The thin membranous covering of the fourth ven- tricle will be visible. If the membrane is broken or showing through it can be seen the pineal gland held on by the Habenula, a rudimentary body lying in the center. Just behind the pineal gland lies the four lobed corpora quadrugemina. The upper portion of the corpus callosum is plainly visible. Trace it forward and down- ward and it narrows down into the fornix. The anterior stem of the fornix turns suddenly downward in front of the optic thalami. A mesial section of the brain will now help in get- STRUCTURE OF THE NERVOUS SYSTEM 29 ting a view of the various parts. This section will show the white corpus callosum, with the fornix just beneath it, and below and behind the thalamus. The space lying under the cal- losum is the third ventricle. The narrow open- ing leading from the third to the fourth vent- ricle is the aqueduct. To the side of the thal- amus and further forward lies the caudate nu- cleus and a part of the striatum or corpus stri- atum. The two prominent bodies attached to the thalamus are called the external and inter- nal geniculate bodies, intimately connected with hearing and seeing. Learn to locate and name the following fis- sures and gyres because of their intimate con- nection with brain localization of functions. Fissure Rolando. Supra Marginal gyre. Angular gyre. Post-central gyre. Pariteo-occipital fissure. Calcarine fissure. Lingual gyres. Central fissure. Fissure of Sylvius. Calloso-marginal fissure. Collateral fissure. Locate the area of the following lobes of the cerebrum: Frontal, Pariental, Occipital and Temporo-Sphenoidal. Sections through the brain will also show 30 PSYCHOLOGICAL EXPERIMENTS the arrangement of the grey and white matter in the cerebrum and cerebellum. For a more detailed study of the brain consult any complete textbook on anatomy. Materials— The head of a sheep or other animal, dissecting instruments, charts and pic- tures of the brain. 5. Spinal Cord The spinal cord can be studied by dissect- ing it from a cat, dog or sheep. The bulb of the brain becomes smaller and passes out of the foramen magnum into the spinal canal as the spinal cord. Coming out in front and behind there will appear groups of nerves joining each other on either side of the spinal column in the form of ganglia. Cutting across the spinal col- umn and cord the same coverings can be dis- tinguished as found around the brain. Dura Mater, arachnoid, Pia Mater, in the above order coming from the outside in. Leaving toward the back or dorsal portion of the cord are the sensory nerves with their cell bodies lying out- side the cord. The motor nerves leave toward the front or ventral side of the cord. A cross section of the cord further reveals a dip or fold of the Pia Mater almost cutting it in two from front to back, the anterior and posterior median fissures. Lying on either side of these fissures two minor fissures can be observed, called the posterior STRUCTURE OF THE NERVOUS SYSTEM 31 lateral fissures and the anterior lateral fissures. These fissures divide the cord into the anterior, lateral and posterior columns. The grey mat- ter of the cord lies roughly in the shape of a letter H with the large portion lying to the front called the anterior horn. The narrowed por- tion lying toward the back is called the poste- rior horn. The grey commissure is the band of grey matter that connects the two sides of the H shape mass. The grey matter is surrounded by white fibrous matter. The relative amount of grey and white matter differs in various por- tions of the cord. Materials — Specimens of the spinal cord, dissecting instruments. 32 . PSYCHOLOGICAL EXPERIMENTS CHAPTER 4. Cutaneous Sensations 6. Cold' Spots The experimenter should explore various portions of the back of the hand of the subject to gain a general idea of the nature of the cold spots. Take some round pointed metallic ob- ject that feels cold and touch lightly various points on the skin. Note the characteristic flash of cold when one of the cold spots is touched. The subjects should not see the ex- ploration during the experiment, but either close or turn away the eyes. The experimenter now proceeds to map an area of 20 mm. square. Immerse a metal cylinder in ice water or expose it to a freezing temperature. After the cylinder h;gs been thoroughly cooled, dry it and explore the charted area carefully. The exploration should be done in a systematic manner, run- ning along imaginary, parallel lines about 1 mm. apart. When the subject exclaims that he feels a pronounced cold sensation, come back to the spot from various directions, thus locating it as accurately as possible. Mark this position with ink, dye or water-color. The marking may be done with a finely pointed brush, or a small tooth-pick. Keep the cylinder cool. After the marked area has been thoroughly explored, place a piece of tracing paper on the skin and copy the marked cold spots in their proper po- sitions. 34 PSYCHOLOGICAL EXPERIMENTS Materials— Pointed metallic cylinder (Fig- ure 1), pen or tooth picks, inks or dyes, ice, tracing paper. ^ V Figure L Metallic Cylinder for Temperature Sense Exploration. 7. Hot Spots Warm the same cylinder, as was used in searching for the cold spots, to a temperature (48°C) that can be tolerated without unpleas- antness. Make a few preliminary explorations to gain an idea of the sensation when a hot spot is stimulated. Mark off the same area that was used for the cold spots. Explore it in the same way, marking the hot spot with a different color from the cold spots. Do not allow the cylinder to rest too long on a hot spot for they may be- come fatigued and fail to respond. For the same reason explorations for verifications should not be attempted too soon after the spot has been located. If possible both the hot and cold spots should be marked on the same chart in different colors. Comparisons are then easily made as to their relative number, position, etc. CUTANEOUS SENSATIONS 35 Report as to the definiteness of the spot and indicate by color or characteristic mark the rela- tive intensity of the warm sensation. Materials — Pointed metallic cylinder (Fig. 1), thermometer, pen or sharp tooth picks, inks or dyes, tracing paper, Bunsen burner, pan for heating water. 8. Touch or Pressure Spots Mount hairs or thin bristles of different lengths and thicknesses on convenient holders or match-sticks by means of glue or sealing wax. (Fig. 2). The various lengths and thick- nesses will permit the exertion of various pres- sures before bending. The amount of these pressures can be measured in grains by applying the end of the hair to one of the pans of a balance. Fig. 2. Hair Mounted for Touch Spot Exploration. All hairs growing out of the skin have a touch spot underlying them, they therefore should be carefully cut off and their point of emergence marked. Select a mounted hair of such a length and thickness that the pressure 36 PSYCHOLOGICAL EXPERIMENTS exerted is very light. Carefully explore an area of from 10 to 20 mm. square. Mark the points where the pressure is felt. Select two more hairs with increasing pressures such that the pressure of the heavier one is somewhat less than what could be felt over the entire area. Mark in a different color the additional pressure spots found with each of these hairs. Transfer these marks to a chart noting the original hair follicles by some characteristic mark. Observe the different kind of sensations as touch end- ings of varying sensitivity are stimulated. Are there other sensations than that of pressure? Are the pressure spots located with an equal degree of accuracy? Materials — Stiff hairs or bristles, match sticks, wax, scale weighing in grains, pen, point- ed tooth picks, inks or dyes, small scissors, transfer paper. 9. Pain Spots Close the hand thus stretching the skin rather tightly over the knuckles. Touch the bent knuckles lightly with a finely pointed ob- ject, like a needle, better still a fine thorn. Can you distinguish pain endings from touch sensa- tions, or does the pain sensation follow that of touch? Describe the sensation. Show the number of pain endings either by chart or counting them within a bounded area around the knuckles. CUTANEOUS SENSATIONS 37 Materials — Fine needle or thorn, pen or fine pointed tooth picks, ink, tracing paper. 10. Charting Pain Spots Bound a small hairless area on the back of the hand. Try to locate the pain endings. The skin may be made more sensitive by softening it with warm water. Thorns mounted on thin T Fig. 3. Thorn Mounted for Pain Spot Exploration. bamboo strips (Fig. 3) are excellent for this work as they do not give temperature sensa- tions. The thin bamboo strips spring back and avoid puncturing the skin which is very impor- tant. Pointed hairs or bristles can also be standardized and used. A chart can be made in the same manner as for the cold and hot spots. Materials — Mounted thorns, pen or finely pointed tooth picks, ink, tracing paper. 11. Temperature Adaptation Place the finger of one hand in water at 15 C (59 F) and the same finger of the other hand in water considerably warmer, say 35 C (81 F).. Take note of the initial sensations then the gradual adjustment. After the adaptation seems complete transfer both fingers into the 3P PSYCHOLOGICAL EXPERIMENTS same water at approximately 25 C (77 F). De- scribe the sensation arising from each finger. Materials — Bunsen burner, pans, ther- mometer. 12. Temperature After Images Place a cold coin on the forehead or on the palm of the hand. Leave it there for 30 or 40 seconds. Remove it and note the after sensa- tions. Are they like the stimulus? Are they uniform? Note the time of the after-sensation. Place the coin on the forehead for one minute; noting the above points; two minutes; three minutes; four minutes; and five minutes. Materials — Coin, watch. 13. Application of Touch, Prick and Electrical Stimulations on Cold and Hot Spots Select a very sensitive cold spot and apply a heat stimulation. What results do you ob- tain? In the same way select a hot spot and apply a freshly cooled Cf^linder, noting the re- sults. Stimulate both the sensitive hot and cold spots by lightly tapping them with a small pointed object or bristle. Select two other hot and cold spots into which thrust a thin, finely pointed needle. Try also the. effect of stimu- lating these spots by means of a weak inter- rupted electrical current. Materials — Pointed metallic cylinder, Bun- CUTANEOUS SENSATIONS 39 sen burner, ice, pointed tooth picks, interrupted electrical current. 14. Pressure Experiment Dip the hand and part of the fore-arm into a rather deep vessel of temperate water. Where is the pressure of the water most distinct? What explanation can you give for the result? Materials — Deep vessel for water. 15. Pain and Touch Spots Stimulate a touch or pressure spot simultan- eously with a pain spot. Compare this sensa- tion to the sensation produced by brushing the tip of the nose lightly by means of a soft brush- or feather. 16. Pain Endings Inside the Cheek Explore the inside of the cheek for pain endings by means of an interrupted current. How do you account for the large painless area? 17. Pain and Temperature Sense Dip the hand into water heated to 50 C (122 F) and note the sensation. Is the temperature sense still present when the stimulus takes on a painful quality? 18. Relation of Extent to Intensity of Thermal Sensation Dip the entire hand into water at 25 C (77 40 PSYCHOLOGICAL EXPERIMENTS F) and at the same time dip one finger of the other hand into water at the same temperature, add cold water as required to one of the vessels till the temperature of the water that is being tested by the finger seems the same as that of the hand. Note the difference in degrees. Materials — Vessels for water, thermometer. 19. Pain Threshold With a pressure scale having a head of known size, press upon some part of the body with a slow uniformly increasing pressure until Fig. 4. Pressure Pain Hala _CUTANEOUS SENSATIONS 41 the subject indicates a feeling of unpleasantness or beginning pain (not how much he can stand) . Read the scale at the moment the report is made, recording the size of the surface applied and the pressure. Compare the results of the pain threshold of other parts of the body. Apply a larger surface to the body and note the results. Materials — A pressure scale, pressure-pain balance or algometer. (See Fig. 4). 20. Touch Discrimination of Two Points. To measure the tactual discrimination of two points use a pair of compasses tipped with rounded points of rubber or hardwood. A good substitute for the compasses can be made by pushing round hard tooth picks through strips of card-board. Measure the distances that the points are apart on a mm. scale. The subject should not watch the experiment, nor should he know the results until the whole experiment has been performed. Select some surface on the fore-arm that is comparatively free from hair and separate the points far enough apart so they can easily be distinguished as two. With as uni- form pressure as possible apply the points to the surface selected, sometimes 1 point, some- times two, in an irregular order. Ask the sub- ject to report the number of points that have touched him. Take at least 10 reports for two points at a given distance. Reduce the distance PSYCHOLOGICAL EXPERIMENTS between the points and repeat the trials. When one point is presented it should always be re- ported correctly, but under certain limits two points will seem as one. Keep reducing the dis- tance between the points until they seem as one. Then increase the distance by a millimeter for each 10 applications of two points until no er- rors occur. In the form of a table, record the space between the compass points, the number of points applied, the number of points reported by the subject, the number of two-points cor- rectly recognized. Repeat this experiment for other parts of the body, not omitting the back of the neck. Compare the results. Fig. 5. Compass with Scale. Materials— Compass (Fig. 5). millimeter measure. 21. Discrimination of a Point from a Line From a piece of thin, stiff card board cut a series of oblongs; 1/2 mm., 1 mm., W/^ mm., 2 mm., 214 mm., 3 mm., zy^ mm., 4 mm., 4^mm. CUTANEOUS SENSATIONS 43 and 5 mm. wide. By pressing the end of the nar- rawest strip against the back of the hand it will be felt as a point. Press each width to the back of the hand ten times, interspersing it occasion- ally with the Yi mm. strip. Have the subject report as to whether it feels as a line or a point. Use wider and wider strips until there are no mistakes as to its being a line. Then repeat with narrower strips until they all feel like points. In a table show the width of the strip used, the replies and correct recognitions. From these reports, establish the shortest line that can be recognized as such. Try other parts of the body in the same manner. Compare the results with those for the recognition of two points. Materials — Thin, stiff card board, millimeter measure. 22. Apparent Distances on the Cheek Take a compass and set its points 2 cm. apart. Draw the points at a uniform rate and pressure from the subject's ear to his lips. Re- port the apparent distances between the points and the apparent rate at various places. Materials — Compass. 23. Judgment of Distance Around the Lips Separate the points of a compass so they can be drawn from one corner of the mouth to the other with the points passing along the out- side of the margin of the lips. Keep the dis- 44 PSYCHOLOGICAL EXPERIMENTS tances between the points constant. Report the apparent distances at various places. Materials — Compass. 24. Aristotle's Illusion Place the hand on a table, palm upward. Have the subject close his eyes while the experi- menter crosses two of the subject's fingers. Touch the adjacent sides of the crossed finger tips with a single small round object. Does it seem like one or two objects to the subject? Touch the outsides of the crossed tips with two similar objects and get a report of the number that seem to be felt. Take a compass and lay the two fingers down side by side and touch the tips with the points separated various dis- tances; on outlines have the subject put dots representing the position of the points. Now hold the fingers crossed and repeat the experi- ment. Prepare a series of small, simple geomet- rical figures, small enough so they can easily be felt by the tips of two fingers lying side by side. Prick a pin from the back side through the intersections of every line. Feel the pin pricks with the tips of two fingers in their normal posi- tion and reproduce the pin pricks with dots on another sheet of paper. Repeat the same ex- periment with the fingers crossed. Some fail to get the illusions because they visualize the crossed fingers and correct the tactual impres- sion. In order to get the most striking results depend as much as possible on the tactual image. CUTANEOUS SENSATIONS 45 Materials — Pencil or any other small round object, compass. 25. Absolute Touch Localization Draw a full size outline of the flexor surface of the subject's left fore-arm, filling in the veins, tendons and other land marks. Give the subject A blunt-pointed pencil to hold in his right hand, hanging at his side. The experimenter should touch the subject's fore-arm with a similar blunt pencil, pressing gently on the point for two seconds. Remove this pencil and have the sub- ject (blindfolded or looking away) place his pencil on as near the same spot as possible. On the sketch record the locations of the original spot touched, the point indicated by the subject, the direction and amount of error. Repeat the experiment for various parts of the fore-arm and other parts of the body. Take care to keep the duration of the touch, amount of pressure and time between touches approxi- mately constant. Materials — Blunt pointed pencils, life size charts. 46 PSYCHOLOGICAL EXPERIMEISTTS NOTES 47 48 PSYCHOLOGICAL EXPERIMENTS^ CHAPTER 5. Gustatory Sensations 26. Nature of Substance Tasted Wipe the tongue dry with a clean cloth or absorbent cotton. See if pinches of salt, sugar and powdered marble can be distinguished. Al- low the tongue to be covered with saliva so as to dissolve part of the powders. Can they be tasted now? Materials — Dry salt, sugar, marble dust, ab- sorbent cotton. 27. Gustatory Acuity Prepare taste solutions of various sub- stances, such as sugar, salt, vinegar, quinine, etc. Strong enough to make the taste easily detected. Place a teaspoonful of one of the solutions (the kind should not be known to the subject) in the mouth and let it touch all parts of the tongue. Have the subject try to identify the solution from the names of the substances in the solutions that could easily be tasted. After the subject has examined the so- lution he should rinse his mouth thoroughly with distilled water. Reduce the strength of the solutions until the subject fails to detect their taste, keeping a record of the percentage of taste material in the solution. This experiment can be repeated beginning with subliminal so- so PSYCHOLOGICAL EXPERIMENTS lutions and gradually increasing their strength until the taste becomes plainly apparent. Materials — Sugar, salt, vinegar, quinine, scales, graduated glass. 28. Reactions of Individual Taste Papillae Draw an outline of the tongue, marking the contour and median lines, and putting in a few easily recognizable groups of papillae, prefer- ably in different locations. From these groups select five easily recognizable prominent papil- lae to be used for the experiment. Prepare 407^ sugar, saturated salt, 8% tartaric acid and 2% quinine solutions. Place these solutions into bottles of like appearance. Add also a bottle of distilled water. Have a large bottle filled with tasteless water in which the brushes can be washed. Have water ready with which to wash the mouth and a receptacle for the rinsings. Take a small pointed camel's hair brush, rinse it in the water, then dry it with cotton. Dip the brush in one of the solutions. The subject at a signal from the experimenter dries his tongue as much as possible against the roof of his mouth. The tongue is then extended and the experimenter quickly dries the papillae to be used by means of a tuft of cotton. The brush is then carefully applied to the papillae, care being taken not to touch the surrounding area. Hold the brush in place about two seconds when the subject can withdraw his togue and make a report. After a few minutes' rest another pa- GUSTATORY SENSATIONS 51 pilla can be stimulated, either with the same or another solution; and so on, until all five have been stimulated. Allow a rest period of a few minutes then repeat the expirement, stimulat- ing the papillae in a different chance order. Stimulate occasionally with distilled water to see that the subject is not merely guessing. Continue until each papilla has been stimulated five times by each of the four solutions. Can the same papilla taste the different solutions? Are confusions common and do they appear with equal frequency for all papillae? Explain results as fully as possible. Materials — Small pointed camel's hair brush, sugar, salt, tartaric acid, quinine, scales, grad- uated glass. Note — A splendid substitute for the small brushes can be made by winding a bit of cotton around the point of a sharp toothpick. These can be discarded after they have once been used. 29. Weak Taste Experiment with the taste solutions after they have been weakened to 20% sugar, 2% salt, .5% tartaric acid, .002% quinine. Record the results with a statement of their clearness, intensity, etc. Materials — Sugar, salt, tartaric acid, qui- nine, means for measuring. 52 PSYCHOLOGICAL EX PERIMENTS 30. Effect of Cocaine on the Taste Papillae Paint a papilla with cocaine and repeat the taste tests. Do not allow the cocaine solution to spread over the surrounding area of the tongue. Materials — Cocaine solution, small brush, taste solutions. 31. Detection of Various Tastes Repeat the stimulation of the papillae with ten different taste solutions and analyze the method of recognizing them. Stop the nostrils with tufts of cotton so as to judge by tastes only and not by odors. Materials — Various taste solutions. 32. Simultaneous Taste Contrast Dry the subject's tongue and apply to one side of it a taste solution, the nature of which the subject is ignorant. The solution must be so weak that the end organs are not stimulated. The strength of these solutions can be tried out experimentally to see if they produce sensa- tions. The subject should have his eyes closed and nostrils stopped. Drop by means of pipettes a drop or two very weak solution of salt on one side of the tongue and on the other a standard (See Exp. 28) solution of sugar. Take care that the solution does not cross the median of the GUSTATORY SENSATIONS S3 tongue. Rinse the mouth of the subject and apply the standard sugar to the side of the tongue on which the weak salt was applied be- fore. Repeat the experiment, using water in place of the weaker solution. Try also a weak solution that is not subliminal. In the same manner use a weak solution of sugar with a standard solution of salt. Materials — Solutions of sugar and salt, pipettes. 33. Successive Taste Contrast Apply a standard (See Exp. 28) solution to the tip of the tongue. After two or three sec- onds rinse the mouth and apply distilled water. Repeat the experiment using instead of the dis- tilled water various weaker solutions of the same taste and of other tastes. Try especially various sugar and salt solutions. Materials — Solutions of sugar, salt, tartaric acid, vinegar, quinine. 54 PSYCHOLOGICAL EXPERIMENTS CHAPTER 6. Olfactory Sensations 34. Olfactory Acuity Dissolve a gram of camphor gum in 1,000 cc. of odorless water. Prepare from this solu- tions of the following strengths: 1:2000, 1 :4000, 1 :8000, 1 : 16,000, 1 :32,000. Place sam- ples of the various solutions in clean test tubes. In tubes of the same size and shape leave sam- ples of pure water. Mark the tubes in such a way that the experimenter can easily identify them but so the subject cannot. Place the tubes in a rack which holds them in a row not too near together. The subject smells of each tube in turn reporting "water or "camphor." Allow considerable time to escape between sniffs and sniff only once at each tube as olfactory fatigue easily sets in. The experimenter can report the strength of solutions for which no errors are made, those for which some errors were made and those always classified as water. The threshold can thus be established. Other odors can also be used and their threshold established. Care must be taken to avoid the room being filled with the odors. Materials — Camphor gum, distilled water, graduated measure. 35. Classification of Odors Zwardemaker's modification of Linnaeus' tables is as follows: 56 PSYCHOLOGICAL EXPERIMENTS 1. Etherial; including fruit odors. 2. Aromatic; camphor, spice. 3. Fragrant; many flowers, violets, sweet peas, etc. 4. Ambrosiac; musk. 5. Alliaceous; garlic, chlorine. 6. Empyreumatic; burning tobacco, toast, coffee. 7. Hircine; cheese. 8. Virulent; opium. 9. Nauseous; decaying animal matter. Above are given as the names of odors with e>.imples for each, supposed to be typical. Get as large a variety of odors as possible and try to classify them according to the above table. Compare your classification with as many oth- ers as possible. Materials — Various substances that emit odors. 36. Olfactory Fatigue Take four or five odors of different character and become familiar with their apparent strength. Plug one nostril with cotton and in- hale one of the odors (eyes closed) until it seems to disappear. The experimenter should then hand him other odors to be examined. What can be said of their relative strength with the first time they were examined? After an interval of several minutes try the original odors again, then fatigue the organs of smell OLFACTORY SENSATIONS 57 with a different odor noting the effect on the rest as before. Materials — Odor solutions. 37. Odor Mixing From a large collection of odors select two in small bottles and pass them rapidly back and forth before the subject's nostrils while he is inhaling slowly. Is the odor from the two a mixture or does one predominate, or does one appear at times to be followed by the other. Continue the experiment with other odors. Try the experiment by holding one odor to one nostril and the second one to the other nostril. Materials — Odors. S8 PSYCHOLOGICAL E XPERIMENTS CHAPTER 7. Labarynthine Sensations 38. Labarynthine Sensations and Movement Place the subject on a platform that can be rotated in the horizontal plane. The subject should be perfectly still with his eyes closed. Rotate him gently and steadily. Does the sub- ject feel that he is being rotated. Increase the speed rather suddenly and it can be noticed by the subject. The subject should move his head and notice the effect of the rotation. Stop the rotation and get the subject's sense of move- ment. Materials — Rotating platform. 39. Labarynthine Sensations and Eye Move- ment Repeat the same experiment with the eyes open and notice the eye movement of the sub- ject as much as you can. Have him give a full report of his feeling, method of accommodation, etc. Materials — Rotating platform. 40. Sense of Vertical Position Strap the subject securely on a table that turns over in a vertical plane. The subject, with his eyes closed should be turned over two or three times. He then is asked to tell when his 60 PSYCHOLOGICAL EXPERIMENTS head is straight down and up without looking. The experimenter should record the position at which the report is made and measure the num- ber of degrees of error. Repeat the experiment turning the subject over in the opposite direc- tion. Materials — Vertical rotating platform. NOTES 61 62 PSYCHOLOGICAL EXPERIMENTS CHAPTER 8. Auditory Sensations 41. Auditory Acuity Go into a quiet room (at night or in a sound proof room) and take a watch that has just been wound or a fall hammer acoumeter for a source of sound. Warn the subject that at times the sound will be audible and at times inaudible. If a watch is used it can be held in the closed hand to make it inaudible. Give the subject warning and then ask him to report when he hears the sound and when he fails to hear it. See that the source of sound, when audible, is in the same position and has in every way the same efficiency. Select a distance from the subject such that the sound is plainly audible, then re- Fig. 6. One Form of Acnometer, the Pendulum can be Dropped from Various Heights for Different Intensities. 64 PSYCHOLOGICAL EXPERIMENTS treat a given distance, each time repeating the experiment. "When the subject fails to distin- guish between the audible and inaudible pe- riods his limit of auditory acuity has been reached. Repeat the experiment, going beyond the limit of hearing and approaching the subject. Average the results of the two distances. Test one ear at a time, stopping the other one lightly with cotton. Materials — Watch, acoumeter, (Fig. 5). tape measure, sound proof room. 42. Auditory Adaptation Place the ends of a rubber tube in each ear. Fig. 7. Tuning Forks, Unmounted and Mounted on a Resonating Box. Carry the tube back of the subject's head and support it on a table or platform. Rest a vi- ^UDITOR Y S ENSATIONS 65 brating tuning fork gently on the tube directly back of the head. Compress the tube so the sound travels only to one ear. As soon as the subject reports that the sound is no longer aud- ible, release the tube and open both paths to the ear. What is the result? Materials — Rubber tube, tuning fork. 43. Sound Conduction Apply the foot of a vibrating tuning fork to the top of the head or to the teeth. Let the fork die down so it cannot be heard, then repeat the above. Another good place to make the fork seem highly audible is on the prominent bone behind the ear (Mastoid Process) . "Why should the sound seem so plain? What conducts it to the inner ear? Materials — Tuning fork. 44. Nature of Resonance Sound a tuning fork without its box. Allow Fig. 8. Resonating Spheres. The small end is placed in the ear and the vibrating body is held before the large end. the tone to die down until it is impossible to hear. Place this fork on its resonator quickly; 66 PSYCHOLOGICAL EXPERIMENTS does it make it audible? WiH the intensity be as great over all resonators? Materials — Tuning fork, resonators. 45. Aural Resonance Hold a vibrating tuning fork before the ear, listen to it dying down until it is impossible to hear it, then insert your finger gently into the opposite ear, or introduce a ball of cotton. Does the sound increase or decrease? Explain the result. Materials — Tuning fork. 46. Ear as a Resonator Sound several tones in the vicinity of fIV. Often a tone can be discovered that seems to have a piercing character. Determine the pitch of this tone. The resonating quality of the ex- ternal meatus may be altered by inserting a piece of rubber tubing about one inch long iq each ear. Note the difference in quality of sounds heard. "What tones does it modify most ? Materials — Tuning fork, musical instru- ments, small rubber tubing. 47. Measuring Wave Length by Resonance Sound a tuning fork over a tall vessel that- is of uniform size throughout. Keep filling the vessel with a little water at a time until the increased intensity, due to resonance, has AUDITORY SENSATIONS 67 reached its maximum. Measure the distance from the fork to the water. If the vessel is tall enough fill until a second and third points of intensity are found. Measure the distance care- fully in each instance. What relation does the wave length bear to the size of the resonating cavity? Materials — Tuning forks, tall cylindrical ves- sels for holding water. 48. Nature of Overtones Pluck the string of a monochord. Touch the vibrating string in the middle with a feather, a narrow twisted tuft of cotton, or strip of paper. Listen carefully for the higher pitched tone pro- duced. What is the pitch of this tone? Trisect the string in the same manner as above. What is the pitch of the tone produced? Can you hear these over-tones without using the brush? Materials — Monochord. Fig. 9. Sonometer or Monochord. 49. Timbre Sound several musical instruments of the same pitch so the subject cannot see them. Can the subject distinguish one from the other? If one is resounded does the subject identify it? 68 PSYCHOLOGICAL EXPERIMENTS Analyze the qualities of the sounds that make possible this identification. By means of res- onators pick out the important over-tones. Materials — Musical instruments, resonators, (Fig. 8). 50. Discrimination of Pitch Sound a tone of a certain pitch, then sound another slightly higher or lower and ask the subject to state whether the pitch is higher or lower. The subject should be seated about 1 meter from the source of the sound and have his eyes closed. Take ten judgments for each pitch difference, giving the higher one first at times and last at times. Gradually increase the difference in pitch until no errors are made. If tuning forks are used record the vibration rates of each pair, and the judgments, if some other source of sound is used, calculate the vibra- tion rates. Strike the forks with blows of about the same intensity with a soft-tipped hammer. The forks should be mounted on their resonators. Damp the vibrations of the one fork completely before the second one is struck. Materials — Tuning forks (Standard 426% vibrations), comparison forks whose vibration rates are 1, 2, 3, 4, 5, 8, 12, 17, 23 and 30 vibra- tions below standard. AUDITORY SENSATIONS 69 51. Tone Character Select tones of various pitch from the high to the low, or low to the high, and describe them in words other than high and low. Describe them as heavy, light, piercing, dull, etc. Sound each tone continuously and, with eyes closed, give the first associations brought to mind. Can they be characterized by words rep- resenting feelings such as gay, sad, lively, etc.? Materials — A series of tuning forks on their resonators. 52. Intensity of Tones Sound a high and low fork simultaneously on their respective resonance boxes. Let them die down until the high-pitched fork can no longer be heard. Stop the low fork. Can the high fork be heard again ? Reverse the process, does it revive the low fork? "What is the nature of a tone in regard to pitch that will overcome another tone? Materials — Tuning forks on their resonators. 53. Upper Limit of Pitch Use a Galton Whistle for this experiment. Care should be taken to have the wind pressure uniform. The subject should seat himself in a comfortable position in a quiet room. Avoid shifting or moving about. The experimenter holds the whistle about three feet away from 70 PSYCHOLOGICAL EXPERIMENTS the ear of the subject. Set it so as to produce a distinctly audible tone. After each blast shorten the whistle until only a puff of air is heard. Record'the length of the gap when the tone has just disappeared. Shorten it a bit more so that the tone is not audible, then lengthen the whis- tle gap until the tone is just audible and again record the length. Get a record of ten measure- ments going each way for your result. Materials — Galton, or Galton-Edlemann whistle. »= Fig. 10. Galton-Edlemann Whistle. 54. Lower Limit of Pitch Take a series of tuning forks that range from 10 to 40 vibrations per second. Sound them close to the ear of the subject, beginning with the lowest, and note the fork of which the vibrations seem to blend into a tone. In the same manner begin with the fork vibrating at 48 per second and take up those that vibrate slower until one is found that ceases to give a distinct tone. Is a tone clearly distingu's'iable from repeated puffs of air? Materials— Slow vibrating forks. AUDITORY SENSATIONS Fig. 11. Slow Vibrating Tuning Fork. 55. Auditory After Sensations Suddenly stop the vibrations of a tuning fork while it is being held before the ear of the subject. Do you get an after sensation ? What is its nature, duration, qualities? Materials — Tuning fork. 56. Beats Take two forks of the same pitch and weight one with a clamp so its vibration rate is reduced slightly. Have each fork mounted on its res- onator. Sound them simultaneously. If there is very little difference in their vibration rate, the beats per second can be counted directly. If the weight on the fork is increased or placed 72 PSYCHOLOGICAL EXPERIMENTS nearer the free end, what results? If the beating rate is increased it becomes a tone of very low pitch. Can you detect this tone? Materials — Two tuning forks of the same pitch, weighting clamps. NOTES 73 74 PSYCHOLOGICAL EXPERIMENTS CHAPTER 9. Visual Sensations 57, Purkinje's Images In a dark room have the subject turn his eyes toward a light colored plain wall so as to expose as much of the white of one eye as pos- sible. By means of a reading glass or any dou- ble convex lens focus the light of a candle on the white sclerotic coat. A shadow picture of the blood vessels of the retina will be visible. Materials — Dark room with light walls, lens, candle. 58. The Blind Spot Place a small cross or x on a sheet of paper and about 7 or 8 cm. to the right of it place a heavy circle, 1.5 cm. in diameter. Close the left eye, look at the cross, then move the sheet of paper back and forth, rotating it slightly and it will be found that at a certain point the circle will disappear. The image of the circle has fallen on the Blind Spot. To find the blind spot of the left eye invert the paper, placing the cir- cle to the left of the cross. Materials — Sheet of paper with the proper designs upon it. 59. Visual Adaptation Go from the sunshine to a darkened room 76 PSYCHOLOGICAL EXPERIMENTS and note the time required to adapt yourself to the reduced illumination. Sit for a time in a dark room, then suddenly turn on a strong light, simultaneously starting a stop-watch; stop the watch when your vision has reached its greatest efficiency for that illumination. If possible, by means of a photometer, standardize the illumi- nation in terms of candle power. Materials — Stop-watch, dark room, photom- eter. 60. Visual Acuity The visual acuity of an individual can best be tested by the use of a special chart, prepared for that purpose. Test one eye at a time, trying all the characters or letters in the line. Proceed from the larger to the smaller characters until a line is' reached in which mistakes are made. Move nearer and repeat the experiment. The subject, of course, will then be able to read smaller characters. The visual acuity is de- noted by a fraction of which the numerator represents the distance at which the letters could just be read, and the denominator repre- sents the distance at which they should be read, as indicated on the test chart. In "normal" acuity the numerator and denominator have the same value. Bright daylight without direct sunshine is usually considered the standard light. For comparisons care must be taken to have the light uniform. Note any differences VISUAL SENSATIONS 11 of the mental attitude as the experiment pro- ceeds. This experiment has many practical ap- plications. Discuss them. Materials — Visual acuity test charts. 61. Discrimination of Brightness of Trans- mitted Light Arrange a box so the light from an electric lamp shines through two translucent windows, by means of reflecting the light with white screens. Record the angle of the screens as these become the basis for calculating the brightness of the window. Get the maximal il- lumination for the windows and record the just discriminal setting of the levers that can be dis- cerned. Use first one and then the other win- dow as the standard. Arrange a head rest so that the subject can hold his eyes directly in front of the apparatus on a level with the win- dows. Study the effect of practice. Substitute colored lights for the white one. Materials — Box, arranged with reflecting mirrors, frosted lamp bulb and glass windows. 62. Visual Difference Threshold Mount a large white disc with a radial slit on a color mixer. Through this slit introduce a smaller colored disc, also slit along a radius. A screen should be set in front of the color mixer 78 PSYCHOLOGICAL EXPERIMENTS when the discs are being mounted and when changes are made so that the subject never sees the discs except when they are rotating. In- crease the amount of color projecting through until the color is noticed and named by the sub- ject. Increase the amount of color until it is plainly visible, then gradually decrease it until the subject reports its disappearance. Record the amount of color actually present each time in per cents of the total circumfer- ence or in degrees. Repeat this experiment with black, grey and colored discs. Materials — Rotator, discs. FiK. 12, Showing method of introducing smaller disc. VISUAL SENSATIONS 79 63. Test for Color Blindness The Holmgreen worsted yarns are usually used to test for color blindness. Take the three large test skeins (pale green, red, rose, Nos. 101, 102, 103) from the rest. Scatter the small skeins over a grey or white background. Give the subject the large pale green skein and direct him to select all the skeins that resemble the standard in color, including all the shades and tints of that color. No two skeins are alike, and an exact match is not required. If the subject includes some grays, browns or reds in his se- lection, repeat the test with red and rose stan- dards. Keep an accurate record of the skeins se- lected as having in them the same color as the standard. The color-blind will include uncol- ored and shades and tints of other colors with the' standard. Avoid the naming of the colors during the test except by way of illustration. Materials — Holmgreen's worsteds, light grey or white cardboard for a background. 64. To Find Original Colors by Means of Pe- ripheral Vision Use purple, violet, green, red, blue, yellow and one or two other colors in this experiment. Fixate on a white spot and by means of a camp- imeter cause the small colored spot or disc to be exposed on all portions of the retina from the 80 PSYCHOLOGICAL EXPERIMENTS center to the outside margin in a straight line in any direction (up, down, right, left). Note how the colors disappear. Do all the discs sud- denly change to a grey or do they take on a color value intermediate between the original color and the grey? Do all colors change to grey before disappearing? Explain results. Materials — Campimeter or perimeter, small colored papers. 13. Perimeter or Campimeter. 65. Charting the Color Areas of the Retina From the former experiment select those four colors that did not change their color value VISUAL SENSATIONS 81 before becoming grey and use them in this ex- periment. Fixate on the white spot and by means of the campimeter cause the colored spot to be thrown on all points of the retina from the center out, the same as in the former experi- ment. At the moment the color disappears stop the movement and note the number of degrees from the center at which you stopped. Then move the spot out beyond this point and take the reading at which the color appears in com- ing back. Take ten of these readings for each position of the campimeter wing (five in each direction). Record readings for at least four positions of the campimeter wing (up, down, right, left) and as many more as time will per- mit. Average each ten readings. Make a chart by locating points at such distances and direc- tions from a center as shown by the averages of each color in its direction. Connect these points with lines of the same color as the disc used in making the record. What can be said of the relative size of the fields of the retina that are sensitive to each of the respective colors? How does the relative size of these fields and the colors they repre- sent compare with the order in which color blindness sets in? What suggestion does this experiment give in regard to evolution of color sensitivity? Materials — Campimeter or perimeter, col- ored papers, retinal charts. 82 PSYCltOLOGICAL EXPERIMENTS Note : On some campimeters it may be nec- essary to reverse the recorded readings in di- rection for the chart. Note the direction of the readings and the direction the colored spot travels from the fovea of the eye and it will soon appear whether the readings should be direct or reversed to be true for the subject's retina. 66. Effect of Distance on Apparent Brightness Place a white disc on a color mixer, 5 to 10 feet away from the subject. Place a sheet of the same paper 30 feet or more away, so situated that it can be seen past the edge of the disc. Take a tube with an opening in it so small that nothing but portions of the near disc and the farther sheet are visible at once. It will be seen that the white farthest removed seems darker. Introduce black with the white disc until it seems to match the sheet 30 feet away. Record several trials in the following form: W---% + Bla---% at---feet=W 100 ojo at feet. Materials — Rotator, white disc, sheet of paper of the same whiteness as the disc, meas- uring tape, tube, measuring disc. 67. Brightness and Intensity Match a black and white mixture in bright- ness equivalent to various samples of colored paper. Take a series of four or five colored ""pers and try to get the same brightness by a VISUAL SENSATIONS 83 mixture of black and white. Use your best judgment. Which seems the brighter, blue or yellow? Red or green? Record equations. R100% = Bla.___%+W----% etc. in intensity of brightness. Materials — Colored papers, rotator, black discs, white discs, measuring disc. 68. Perception of Colors On a white or better a grey background 30 c. m. square mount 100 small squares of colored paper. 'Ihe colored papers should be V/z c. m. square and so arranged that they are l|/2 c m. apart in each direction. Use ten colors : — olack, blue, brown, green, grey, orange, pink, purple, red, yellow. Have each color appear 10 times on the card, arranged in a chance order with no two squares of the same color appearing in suc- cession in either direction. Have the subject read the colors over several times in order to familiarize himself with their names. To conduct the experiment, have the subject lay the card before him, colors down. Then upon a signal from the experimenter the subject turns the card up and names aloud the colors as rapidly as he can. The experimenter follows him and in case any color is incorrectly named, says "no." The subject is required to give the correct name before proceeding. A record is 84 PSYCHOLOGICAL EXPERIMENTS kept of the time required to correctly name the 100 colors. The card can be rotated 14 of the way around for each successive experiment, thus ehminating memory effects. Materials — Colors mounted on a card board according to the directions given above. 69. Positive After Image The rapid movement of a stick to and fro causes it to spread out in a fan-like shape. Where is this image most prominent, near the stick or farther away? Mount a white disc Fig. 14. Disc arranged to show positive afterimage. with a heavy black line along a radius, on the color mixer and slowly increase the speed of rotation until the line just spreads over the disc, showing no flicker. Get the number of rotations per second. From this data calculate the duration of the positive after-image. VISUAL SENSATIONS 85 Materials — Rotator, white disc, speed indi- cator, watch. Fig. IS. Discs arranged for producing tints. 70. Tints Take a blue disc and a white disc of the same size, arrange them so you have the following combinations: Bu. 75% and W. 25%. Rotate the discs and record the results in form of equations. Thus : Bu75% + W25% = ' (Name the color from the standard colors, a color chart, silk samples or from your knowl- edge of color names). Shift the discs so as to get Bu.50^o + W50%; Bu. 25fo + W75%. 86 PSYCHOLOGICAL EXPERIMENTS Use also yellow, red and green with the white mixtures and record the results. \/\J\n!fe /ot^J^'-i'"^"--^" Red Green Black Fig. 16. Diagram showing the relations of various colors, shades and tints. Saturated colors are located on the plane of the two cones. Opposite each color is its complementary, i. e., if the color opposite were mixed with it a grey would be produced. The adding of white produces tints until white is reached at the apex of the top cone. In the same way shades are shown on the lower cone of the diagram. A line running from one point to the other should represent all shades of grey from white to black. VISUAL SENSATIONS 87 Materials — Colored discs, white discs, meas- uring disc, samples of standard colors and tints, rotator. 71. Shades Take a blue disc and combine it with a black disc of the same size so that you have the fol- lowing combination : Bu. 75% + Ba. 25%. Fig. 17. Discs arranged to produce shades. Rotate the discs and name the resulting color. Shift the discs so as to get Bu.50%+Ba.50%; Bu. 25%+Ba. lb<^c. Repeat the experiment, using yellow, red and green with the black mixtures and record the results. PSYCHOLOGICAL EXPERIMENTS Materials— Colored discs, black discs, meas- uring disc, standard colors and shades, rotator. 72. Mixing Various Colors not Complementary- Mix red and blue in the following propor- tions and name the resulting colors: R25%+Bu. 75fo=? R50% + Bu. 50%=? R75%+Bu.25%=? In the same way combine blue and green ; green and yellow; yellow and red. Materials — Colored discs, measuring disc, standard colors, rotator. 73. Mixing Blue and Yellow to Produce Neu- tral Grey Mount two large discs of blue and yellow on the color mixer, on them mount smaller black and white discs. Change the relative amounts of blue and yellow and the black and white un- til the colors produced by both sets of discs is the same or matches. Measure each disc and state the result in the form of an equation. Thus: Bu %+Y— -%=Ba % + W- — %. Note: Because the colors may not be pure a third may have to be added to the color group. •Materials — Colored discs, small black discs, small white discs, rotator, measuring disc. VISUAL SENSATIONS 89 74. Fig. 18. Discs arranged to produce a grey. Mixing Red and Green to Produce Neutral Grey In the same manner as indicated in the pre- vious experiment get a red and green mixture to match a mixture of black and white. A third color may have to be added because of impurity of the green or red. Fig. 19 shows the method for mounting the discs and adding a third color. Materials — Colored discs, small black discs, small white discs, rotator, measuring disc. 75. Mixing More Than Two Colors to Pro- duce a Neutral Grey Take 50% of each of the colors used in the 90 PSYCHOLOGICAL EXPERIMENTS Fig. 19. Discs arranged to produce a neutral grey. Method of introducing tliird color is shown. experiments, Nos. 73 and 74, and place them on the color mixer. Then divide the black and white ratios in each of the above mixtures by two, adding the quotients and mount the small black and white discs on the colored discs in the ratio indicated by these sums. Rotate and note if the mixtures match. How can this be said to be a check on the former mixture? If they do not match, what reasons can you give for the result? Materials— Colored discs, small black discs, small white discs, rotator, measuring disc. VISUAL SENSATIONS 91 76. Color Contrast Place a strip of grey paper 10 cm. long and 1 cm. wide on a sheet of red paper. Look at the small strip a few moments and note the color that may seem to appear on it. Cover the whole sheet with a sheet of very thin tissue paper. Does this increase the amount of color that ap- pears on the grey strip? Why? By means of a color mixer upon which are mounted a black, white and colored disc, match the appearance of the grey strip. Get five or more grades of grey from a very light grey to a very dark grey and record the amount of simultaneous contrast color produced on each by the equations gotten from the color mixer. Try yellow, blue, green and other colors. What relation does the amount of induced color bear to the grey and the colored background? Materials — Colored sheets of paper, small grey discs or strips of paper, tissue paper, black, white, colored discs, rotator, measuring disc. 77. Brightness and Contrast Color Arrange a set of discs on a rotator as follows: 1. A large colored disc. 2. An intermediate size of black and white djscs (cut on a radius). 3. A small disc the same color as no. 1 . (See Fig. 20). When these discs are rotated it will give a grey band upon which a contrast color will ap- 92 PSYCHOLOGICAL EXPERIMENTS Fig. 20. Showing arrangement of discs for contrast color. pear. Change the relative amounts of black and white until the most color is induced on tfic grey. Record the amount of black and white. What can you say of the relation of the amount of black and white to the brightness of the colors? Can the brightness of colors be meas- ured in terms of the amount of black and white upon which the most contrast color appears? Materials — Large colored discs, small col- ored discs, intermediate black and white discs, rotator, measuring disc. 78. Brightness Contrast Place some pieces of grey paper, 10 cm. long and 1 cm. wide on colorless backgrounds of dif- ferent brightness. Note the brightness con- VISUAL SENSATIONS 93 trast, describing its nature. Does the contrast increase or diminish as you look at it? Is there a change in the size of the pupil? How can the pupillary effect be eliminated? Materials — Grey paper, various white papers. 79. Contrast Color in Shadow Provide two sources of illumination for a dull white surface. This can be done by means of openings through a screen before a window or apertures in a dark room. Between these sources of light on a white surface place a cane, rod or ruler vertically so that two shadows are cast on the white surface, one from one open- ing in the screen and the other from the other.' Place a colored glass before the one opening and enough clear glass before the other to make the colorless illumination of about the same in- tensity as that of the colored light. Note the contrast color as it appears in the colorless shadow. Change the colors by means of other glasses. Change the relative intensities of the two sources of light. Carefully note the results in each case. Materials — White sheet of paper, ruler or pencil, colored and plain glass. 80. Negative After Image Look steadily for a few moments at a small white disc on a black or dark grey background. Then look steadily at a dot placed on a neutral 94 PSYCHOLOGICAL EXPERIMENTS grey background. What image forms around the dot? Take a stick, that has a glowing coal on the end, into a dark room and wave it slowly in a large circle. Immediately following the stick will be the positive after-image followed by a dimmer negative image. Note its color in comparison with the positive image. Try to get after-images of various objects on various back- grounds. Also try to get the after-image with the eyes closed. Materials — Small white disc, blac)< or grey background, glowing fagot. 81. Effect of Time of Fixation on the After Image Make a black background about 40 cm. square. On the center of this background place a white square 10 by 10 cm. In the center of this white square should be a black disc or dot about 1 cm. in diameter. This is the background from which the stimulus is received. For a back- ground upon which the image is to be projected arrange a card board or sheet of paper with a neutral grey color (40 cm. square) on the center of which has been placed a black disc 1 cm. square. Look at the stimulus 5 seconds, then look at the projection background, telling your VISUAL SENSATIONS 95 partner when the negative after-image appears and disappears. By observing a watch the ex- perimenter can record the time of appearance and the time of its non-appearance until the after-image ceases to appear. A good way to record these times is to put down the number of seconds that have elapsed as the subject calls out the disappearance and appearance of the after-image, making a — sign over the numbers denoting the absence of the after-image. Look at the stimulus 10, 15 and 20 seconds and record the results as above. Materials — Card board backgrounds, colored squares, small discs or dots arranged as above. 82. Effect of the Stimulus Field on the After Image Use the same apparatus as directed and de- scribed in experiment No. 81. Instead of the white square upon the black background, use it upon various colored backgrounds; also use various colors of the small squares. Note the duration, color and nature of the after-image. Materials — Same as in Experiment No. 81, and colored squares. 83. The Effect of the Background Field on the After Image Use the same apparatus as in previous ex- periments. Instead of the neutral grey back- 96 PSYCHOLOGICAL EXPERIMENTS ground upon which to project the after-image use other shades of grey and also colored back- grounds. Record the duration and color of the after-image. Materials — Same as in Experiment No. 81, grey and colored backgrounds. The last three experiments can well be com- bined into one experiment. In the form of a table the records should show, the length of time of the stimulus, the stimulus color, the color of the background around the stimulus, the color of the background upon which the after-image is projected, the duration of the after-image, the color of the after-image, and any peculiari- ties that occur. NOTES 97 98 PSYCHOLOGICAL EXPERIMENTS NOTES 99 100 PSYCHOLOGICAL EXPERIMENTS CHAPTER 10. Movement 84. Tapping Test Direct the subject to tap, by means of a metal rod, on a metal plate as rapidly as possi- ble for 15 seconds. Record the number of taps by means of an electric counter which is con- nected in series with batteries, the brass plate and the rod. Materials — Metal plate, metal rod, electric counter, batteries, wires and connections. 85. Detection of Passive Movements Bare the arm to above the elbow and lay it on a hinged board (Fig. 21) which is moved by means of a windlass at the top. How many Fig. 21. Apparatus for detecting passive movements. degrees up and how many degrees down can the board be moved before the movement is 102 PSYCHOLOGICA L EXPERIMENTS detected? Where do you begin to feel the movement? Do you detect a sensation of ten- sion preceding that movement? Analyze the source of the sensations as closely as you can. Take a record of the number of degrees in each direction 5 times, 10 in all. Materials— Hinged board, protractor. 86. Right and Left Handedness The strength of the right hand as compared with the left hand can be measured by means of a dynamometer. Grip as hard" as you can Fig. 22. Hand Dynamometer. with the right hand, wait just one minute, grip again, wait a minute again and then grip. Ave- rage the three readings for the grip of that hand. Repeat the experiment for the left hand. Compare the two. Compare the results of a right handed person with one who is left handed. .Materials — Hand Dynamometer.;. : MOVEMENT 103 87. Sense of Movement Move the finger slowly and carefully; note all the sensations that go into the conscious- ness of the movement. Apply a strong yet not painful interrupted electric current to the joint and repeat the experiment. Materials — Interrupted electric current. 88. Feeling of Resistance Fit a band over a finger of the subject's hand to which a thread with a weight is at- tached. Blindfold the subject and have him hold his arm out horizontally away from the body and slowly lower the weight. When tEe lowering has begun the experimenter should noiselessly lift the weight. What sensations does the subject get? Carefully record your experiences and offer an explanation. Materials — Weight suspended with a thread. 89. Steadiness Test Drill a series of holes, 32, 20, 16, 13 and 11, sixty-fourths of an inch in diameter in a brass plate. Cover one end of a metallic rod one- eighth of an inch in diameter with a hard rubber handle. To the rod attach a flexible electric conducting cord which is connected with dry batteries, an electric counter and the brass plate in series. Instruct the subject to hold the rod in the holes without touching the brass 104 PSYCHOLOGICAL EXPERIMENTS plate, for a period of 15 seconds after a pre- paratory signal has been given 3 seconds pre- vious. The subject's hand and arm should be free from support. Every time the brass plate is touched a record is made by the counter. The click of the counter warns the subject that he must immediately remove his rod from the brass plate. The size of the hole and the num- ber of contacts in 15 seconds form the basis of the record. Use right and left hands. Materials — Brass plate with proper sized holes, metallic rod, flexible lamp cord, batteries, electric counter, connections. 90. Steadiness and Accuracy Mount two straight copper or brass strips about 40 cm. long so they converge until they will just bind a metallic stylus at the end. (Fig. 23). The open end should have the strip 5 times the diameter of the stylus apart. The :ia Fig. 23. Apparatus for testing steadiness and accuracy. metallic stylus, a dry battery, a sounder and the two metal strips should be connected in series so that when the stylus touches one of the strips it will make a circuit. Try to draw the stylus as far between the MOVEMENT 105 metal strip without touching as possible. As soon as the sounder indicates that a side has been touched record the distance from the open end. Repeat the experiment 10 times. Try different positions right and left hand, rested and fatigued conditions, etc. Materials — Brass strips, properly mounted, metallic stylus, batteries, sounder, millimeter scale. 91. Judgment of Weight Bare the arm and support it in a comfortable resting position. Close the eyes and have the experimenter lay a weight on the forearm, after having placed a piece of felt on the arm. Report various experiences that give informa- tion leading to a judgment of the weight. After a brief rest repeat the experiment with a rather heavy and rather light weight. Materials — Felt, weights. 92. Judgment of Weight with an Anaesthetic Skin Spray the skin with ether and repeat the judgment of weight experiments. Carefully compare your experiences with those of the previous test. « Materials— Felt, weights, ether, atomizer. 106 PSYCHOLOGICAL EXPERIMENTS 93. Size Weight Illustration Take a very small box or bottle (made opaque by covering it with paper) and fill it with shot or sand. Take a large box or bottle (opaque) of the same general shape and fill it until it appears to be the same weight as the small one. Weigh each box and record the difference in weight. This difference in weight is the amount of illusion produced by the dif- ference in size. Repeat the experiment 10 times, averaging the results. It is best for the subject not to know the result until the end of the experiment. Materials — Boxes, sand. 94. Fatigue, Intermittent Contraction By means of an ergograph exercise a muscle Fig. 24. Metronome. MOVEMENT 107 or set of muscles by pulling against a resis- tance, keeping time with a metronome. Be sure to pull as hard as possible each time. Get a record of these pulls on a piece of smoked paper if possible. Study the records, noting the warming up period and the "second breath" effect. Change the interval between pulls and note the effect. Materials — Ergograph, metronome. 95. Fatigue, Constant Contraction Pull against the resistance as hard as you can and hold this contracted position of the muscles as long as possible, recording the re- laxation by means of a curve. Materials — Ergograph. 96. Rest Fatigue a muscle by intermittent contrac- tions, rest 5 seconds and then begin again. Can you pull as much or can you continue as long? In the same way investigate the effect of 10, 20, 30, 40, 50, 60, seconds, 2, 5, 10, 15, 20, and 60 minutes rest intervals. Discuss fatigue and rest in the light of your data. Materials— Ergograph, metronome. 97. Practice Prepare a target at which large marbles are to be thrown. Behind it a sheet of carbon paper 108 PSYCHOLOGICAL EXPERIMENTS is to be placed and a copy of the front target. Throw at the center of the target 10 times; remove the copy behind the carbon paper, in- serting a new one and throw 10 times again. Repeat the experiment until sufficient data is obtained. Measure the amount of error on each successive target and plot a curve showing the amount of improvement with each series of 10 trials. Other practice and learning experi- ments can easily be devised such as, the speed of typewriting, running a given distance, tak- ing short hand notes, etc. Materials — Marbles, target, carbon paper. 98. Learning New Motor Coordinations Place a paper, upon which is the colored outline of a six pointed star, on the table a little out of the true vertical and horizontal positions. Place a mirror on the table a little beyond the paper that is inclined^ about 5 de- grees from the vertical. Place a screen before the subject over the drawing so the draw- ing can be seen nowhere but in the mirror. Have the subject take hold of the pencil and as- sist him in putting it to the starting point. Ask him to trace the outline as rapidly as possible, never stopping the pencil. Start a watch and record the time required to get around the star. The quality of the drawing is to be considered as well as the time required. Repeat the experiment say 50 times and MOVEMENT 109 draw a practice curve. Repeat the same ex- periment, but instead of following a figure already drawn, draw a rectangle with its diagonals. Materials — Outlines of clamps, screen. a star, mirror. 110 PSYCHOLOGICAL EXPERIMENTS CHAPTER 11. Perception 99. Reversible Figures Look steadily at some reversible figures, such as the staircase figure, the outline of a Fig. 26. cube, the open book figure, etc. What is the effect of looking at different points of the figure first? What effect does a predetermined idea 112 PSYCHOLOGICAL EXPERIMENTS of the position have upon the way you see the figure? Fig. 27. Fig. 28. PERCEPTION 113 Look steadily at the figures for some time and by means of a metronome time the image in each position. Do the reversals occur more often as time goes on? Give as full as expla- nation as possible. 100. Measuring Amount of Illusion Mount three Dart head shaped cards on a slide about 1 meter in length. Fig. 29. a b c The center figure (b) should be mounted on a movable slide which can be actuated by means of cords by the subject seated about 10 feet away. Move (b) back and forth until its central point seems equidistant from (a) and (c). Measure and record 10 such attempts at this central placing 5 times toward (a) and 5 times from (a) toward (c). What effect does practice have on the amouat of illusion? What is the cause of the illusion? Materials — Sliding figures, meter stick. 101. Puzzle Pictures Examine a puzzle picture. Record your 114 PSYCHOLOGICAL EXPERIMENTS introspections as you are finding the hidden forms. Note the time it takes to find the pic- ture the first time. After 5 or 10 minutes take up the same pic- ture. How long does it take to find the hidden figure this time? What can you say of the clearness with which you saw the hidden figure the second time as compared with the initial image that you got the first time? Materials — Puzzle pictures, watch. 102. Stereoscope Take the frustum of a cone, (a large cork) rrrr}, ;'it\ ''''''' ,^_ ■""--^y '0^- — "v;.--"-;-:?^.^^"::::; 1 r,V ',Vi ---J 6 Fig. 30. Plan of the Wheatstone Stereoscope. Fig. 31. Wheatstone Stereoscope. PERCEPTION 115 and mount it small end toward you on a level with the eyes. Hold your head in one position and look at it first with one eye then with the other. Represent the planes of the base and top by means of circles in their respective rela- tive position as they seem for each eye. Draw the pictures for each eye on a slip of paper the size of a stereoscope slide. Locate the center of the drawings about 3 inches apart. Place this slide you have made in a stereoscope. Do you get the sense of perspective? In the same way make a drawing of a sphere with a meridian upon it. Make a slide that will show the small end of the frustum of a cone pointed away from you. O-Q-^rrr o-d-^ :----'i Fig. 32. Plan of the Brewster Stereoscope. Fig. 33. Brewster Stereoscope. 116 PSYCHOLOGICAL EXPERIMENTS Explain the workings of a Brewster stereo- scope. Materials — Drawing instruments, frustum of a cone, globe or sphere, stereoscope. 103. Sterescope Take a series of slides representing fusion, partial fusion, geometric forms in perspective, retinal rivalry, binocular color-mixing, stereo- scopic lustre, etc. Number and classify the Fig. 34. Fig. 35. PERCEPtlON V" wA Fig. 36. 117 I Fig. i7. "N/- Fig. 38. 118 PSYCHOLOGICAL EXPERIMENTS ■^v/ ® Fig. 39. \^' H N a x\_ Fig. 40 Fig. 4L PERCEPTION 119 coLoa COLOR Note: Fig. 42. All the examples of stereoscopic views are J/2 size. cards stating what they show and exolain the results. Make drawings showing the principles upon which the Wheatstone, Brewster and other forms of the stereoscope operate. Materials — Special stereoscopic slides. 104. Other Forms of Stereoscopic Vision Take a pair of glasses, one red and one green leiis and pictures that have printed ster- eoptically for this effect in red and green. Do you get perspective? In terms of binocular vision and the principles of the stereoscope explain how the effect is gotten. What happens if you reverse the glasses? Materials — Special pictures, eye glasses with one red and one green lens. 105. General Stereoscopic Slides Look at a set of stereoscopic slides as if you 120 PSYCHOLOGICAL EXPERIMENTS were looking through small windows upon a dis- tant view and then answer the following ques- tions: 1. In gaining an idea of a new place, com- pare the value of the stereoscope with the pro- jected picture, a black-white picture and a colored picture. 2. Do you get a clear sense of perspective? 3. Do you see the picture as natural size, far away or miniature near by? 4. Do you get the best effects right after looking or after looking some time? 5. Do you get a vivid sense of being actu- ally at the place? 6. In what subject matter would stereo- scopic slides be of value? Materials — Stereoscopic slides, stereoscope. 106. The Exposure Apparatus The "exposure appartus" is a screen, behind which is placed the object to be exposed. The screen falls and affords a view through a hole in itself at the objects behind. The exposure should be so short in time that it is impossible for the eyes to make two fixation pauses — i. e. to look at two separate points of the object. About one-fifth of a second is the longest time that can be allowed in these experiments. PERCEPTION 121 In using this apparatus you may see how much is perceived in a single exposure (method of accuracy), or you may count the number of repeated exposures needed to get a correct perception (method of time) ; or you may very well combine the two methods in which case you will have a series of answers from the sub- ject, probably increasing gradually in accuracy till perfection is reached. The series of imper- fect perceptions give some idea of the process by which percepts grow from the vague to the definite. Draw a diagram of the instrument and ex- plain its use. Materials — Exposure apparatus. 107. Perception cf Irregular Forms Find the greatest number of dots, irregu- larly placed, that can be counted by one expos- ure; and the effect of repeated exposures on the accuracy of estimation of larger numbers than can be correctly perceived in a single ex- posure. Provide slips of paper, of suitable size to fit the instrument, all of the same size and shape, and with the matter to be exposed al- ways at the same part of the slip : the slips are also to be inserted in the same position, so that the observer will, after a little practice, know exactly where to look. Prepare slips with dots in irregular groups, from 3 to 12 in number, and expose them to the subject, who is not to m PSYCHOLOGICAL EXPERIMENTS know beforehand how many dots are on the sHp. If he perceives the number correctly, record the fact; if incorrectly, give him further trial till he is sure of the right number. Take care not to give him any external aid. Record all his answers, so as to state, at the end of the ex- periment, within what limits his errors lie at each stage. Try to make out the course of progress from less accurate to more accurate perceptions of the number. Materials — Exposure apparatus, prepared slips of paper. 108. Perception of Regular Forms By means of coordinate paper, prepare dot figures of varying degrees of regularity, but all containing about the same number of dots. Determine the number of exposures for each figure. Materials— Exposure apparatus, slips of paper, prepared with regular figures. 109. Perception and Reproduction Use material similar to that in the last ex- periment, but require the subject, not simply to count the dots, but to reproduce the figure, locating the dots on coordinate paper. After each exposure, the subject attempts to duplicate the figure which was shown him Preserve his attempts in their order and exam- PERCEPTION 123 ine the development of an accurate percept with the repetition of the exposure. Materials — Exposure apparatus, prepared slips of paper. 110. Perception of Lines Repeat the preceding experiment with this difference, that the figures are made of lines. Prepare a series of such figures, running from very simple to fairly complex. Most of these figures should be meaningless, but one or two geometrical forms or drawings of objects may be introduced, and the effect noted. Materials — Exposure apparatus, slips of paper with line drawings. 111. Perception of Various Forms of Material Correlate the results of these three experi- ments; that is, compare the results for all the individuals of the class, to see how those who have a wide field of clear vision read fast and take large bites of the reading matter. 112. Speed of Reading Select a passage of reading matter and by means of a stop-watch, determine the speed of reading for a story and a scientific passage. Reduce your figures to fractions of a second per word. Materials— Reading matter, stop-watch. 124 PS YCHOLOGICAL EXPERIMENTS 113. Visual Span in Reading Compare the extent of the horizontal field of clear vision, as determined in experiment 108 with the amount of reading matter covered in one eye fixation in reading. The average amount can be estimated from the number of pauses per line. The pauses in the eye move- ments can easily be seen and counted. Some- times it does not disturb the reader so much if the experimenter counts the eye movements in a mirror so adjusted as to plainh'^ show the reader's eyes. Does the amount read in one reading pause equal the amount included in the field of clear vision ? Materials — Reading matter, mirror. 114. Correlation of Visual Span in Various Forms of Material Correlate the results of these three experi- ments; that is, compare the results for all the individuals of the class, to see how far those who have a wide field of clear vision read fast and take large bites of the reading matter. 115. Visual Span for Different Kinds of Print- ed Matter The amount of various sorts of printed matter that can be grasped at a single exposure, can be measured on the exposure apparatus. Use miscellaneous letters, nonsense syllables, disconnected words, phrases, and finally, PERCEPTION 125 phrases in context. For the last make the sub- ject familiar with the context before the ex- posure. Put more matter on the screen than can be perceived. Repeat the experiments, averaging the results for each sort of printed matter used. Materials — Prepared reading matter, ex- posure apparatus. 116. Perception of Letters Prepare a sheet upon which all the letters of the alphabet are so arranged that each letter appears 10 times in four lines. Repeat this until every letter appears 50 times. Arrange the letters in a chance order, taking care that no one letter appears twice in consecutive order. Give the subject a letter which he is to can- cel every time it appears. Record the time it takes to cancel the given letter. If any are Fig. 43. Illusion of direction. 126 PSYCHOLOGICAL EXPERIMENTS Fig. 44. Illusion of direction. missed calculate the time per letter required for those cancelled and add it for each letter missed. This then becomes the final recorded time. A record can also be kept of the time per letter. Does the letter used make a d'^^-^irence in time? Materials— Prepared list of letters, stop- watch. 117. Illusions of Direction Study the figures giving as full an explana- tion as possible. Draw other figures that pro- duce illusions. 118. Illusions of Extent What factors enter into the cause of an •Ilusion of extent? Study the figures and ex- plain the illusion and its causes. PERCEPTION 127 Fig. 45. Illusions of extent. 128 PSYCHOLOGICAL EXPERIMENTS CHAPTER 12. Attention 119. Masson Disc Experiment Take a disc of white card-board from 20 to 25 cm. in diameter. Along one radius paste a series of small black squares 5 mm. by 5 mm., 5 mm. apart. This disc is known as a Masson disc. Place the disc on a rotator and run it at a speed of approximately 2,000 revolutions or more per minute. Each black square will pro- duce a faint ring of grey on the surface of the disc. The rings will be fainter and fainter toward the circumference of the disc. Fig. 46. Kymograph. 130 PSYCHOLOGICAL EXPERIMENTS The observer should seat himself about two meters from the rotating disc and place his hand on a bulb connected with a recording tambour writing on the slowly revolving drum of a kymograph. The observer should press on Fig. 47. Masson Disc. the bulb when the greatest number of rings are visible on the disc and release his pressure as the number of visible rings decrease. A time line in seconds or fifths of a second should also be recorded simultaneously with the tambour line. This apparatus will measure the fluctua- tions of attention, to a visual stimulus. Note the effect of distracting noises. Do you get a regular rhythmic fluctuation? What variations occur? It is also interesting to re- cord a breathing and pulse tracing and work ATTENTION 131 out the relation of the fluctuations of attention to, changes in breathing and heart beat. Materials — Rotator, Masson disc, kymo- graph, recording tambour, time-marker, bulb. 120. Attention in Hearing Substitute for the Masson disc in the former experiment a watch so far away that its ticking can scarcely be heard. Does its ticking fluc- tuate in the same way? This experiment must be carried on in a very quiet room, or better still, a sound proof room. Materials — Watch, kymograph, tambour, time marker, bulb. Fig. 48. Pneumograph for recording breathing. 132 PSYCHOLOGICAL EXPERIMENTS CHAPTER 13. Perception of Time 121. Rhythm and Time Sense Connect a telegraph key in such a way with an electric recorder so that taps on the key can be recorded on the drum of a kymograph. A time line in fifths of a second should also be traced. Start a metronome and let the observer tap on the key synchronously with it. Let the metronome run for, say, 20 beats, then stop the metronome. The observer is to continue his tapping at as near the same rate as possible. What intervals are reproduced most accurate- ly? Do the reproductions tend to slow up or increase in speed? Materials — Telegraph key, electric recorder, kymograph, metronome. 122. Rhythm and Time Arrange an apparatus giving beats of the same intensity so the time interval between them differs. Let the space between the dots represent time, then some of the following combinations can be arranged: 134 PSYCHOLOGICAL EXPERIMENTS Other combinations can be tried and their effect studied. A regular beating metronome can be placed in a box, the lid of which can be opened and closed to produce the intervals. Materials — Metronom^e, box with hinged lid. 123. Subjective Rhythm Take a metronome, whose beats are equal in quality and intensity, and set it at various rates. Record the feeling that the various rates give you, such as tiresome, pleasant, ex- citing, etc. The experimenter should note any accompanying swaying or other movements on the part of the observer. Materials — Metronome. 124. Objective Rhythm Inclose the metronome in a box with a lid that can be opened and closed silently thus accenting various beats. In this way produce the common measures such as Trochaic Iambic Dactylic Anaspestic Cretic Study them in regard to their subjective effect. Accent 3, 4, 5, etc., bears in a series PERCEPTION OF TIME 135 with intervals of 2, 3, 4, 5, etc., of unaccented beats intervening. Do these series all give the rythmic effect? Materials — Metronome, box with hinged lid. 136 PSYCHOLOGICAL EXPERIMENTS CHAPTER 14. Reaction Time Experiments The term 'reaction' in psychology means a movement made in response to an external stimulus. The time of a complete reaction or 'reaction time' may be devided into five parts; (1) The latent period in the sense organ re- ceiving the stimulus, (2) the time consumed in the conduction of the impulse from the sense organ to the appropriate sensory center of the Fig. 49. Hipp Chronoscope. 138 PSYCHOLOGICAL EXPERIMENTS brain, (3) the time consumed in cortical elab- oration or the association process, (4) the time consumed in the conduction of the impulse from the motor area of the brain down to the cord and out to the striate muscle that is to make the movement, (5) the latent period of the muscle itself. Various methods are employed for the meas- urement of 'reaction time.' The graphic method, or some form of a chronoscooe, are usually used in the laboratory experiments. Whatever form of apparatus is available, it is important to master its construction and use. Learn to adjust it properly and acurately. Remember that the time intervals to be meas- ured are short, therefore every precaution must be taken to assure accurate results. All results should be averaged and the mean variation of the individual reactions from the average found. Always take a few preliminary records to see that everything is in good working order and to see if the problem is clearly understood. 125. Natural Auditory Reaction Time The subject should seat himself in a natural, comfortable position and lay his finger lightly on the button of the reacting key. It is best for him to close his eyes so as to avoid shifting of the attention. The experimenter having REACTION TIME EXPERIMENTS 139 n n s- 3 a o in n O 3 a. 140 PSYCHOLOGICAL EXPERIMENTS adjusted the apparatus says "readv" or gives some other preliminary signal. After the signal he waits from one to two seconds and then gives the sound stimulus. The subject presses the button as quickly as he can after haying heard the stimulus signal. While his record is being made by the experimenter he can take notes of his introspections. The subject should not know what his records are until the close of the experiment. It is well for the two members of the experiment to take turns at being sub- jects for the experiment so as to avoid fatigue effects. Take 100 records for each subject. Make careful notes as to the nature of your at- tention the agreement of what seems to be very short and very long times with the actual recorded times, the cause of premature reac- tions, etc. Materials — Chronoscope, with accessories for auditory stimuli. 126. Auditory Sensory Reaction Time The sensory attitude is a preparation to ob- serve the stimulus as well as to react. There is a focus of attention on the stimulus. The subject is certain the proper stimulus has been given. He then reacts as quickly as 'possible. It is hard to describe this form of reaction. The student can likely discover what is meant in the trial series of experiments. After feeling that you are conscious of the emphasis of at- REACTION TIME EXPERIMENTS 141 tention on the stimulus, voluntarily assume this attitude and record 100 reactions. Take them in sets of 10 or 25 with rest periods between the sets. Describe, as nearly as you can, your at- tentive attitude. Did you make any premature reactions? Use the same stimulus as in the natural auditory reactions and observe the same precautions. Materials — Chronoscope, with accessories for auditory stimuli. 127. Auditory Motor Reaction Time The usual motor attitude consists solely in a preparation to make the movement, not to ob- serve it as it occurs. It is often said that t\e motor attitude for reacting consists in the at- tention being focused on the movement. This must not be interpreted in the sense oT observ- ing the movement itself, but of gettine your- self mto the best motor readiness for the move- ment. The stimulus comes on as a sort of "shock" setting off this movement for which you have prepared yourself. As compared with the normal or natural reactions the voluntary motor attitude is characterized by a greater feeling of effort. Describe your attentive atti- tude as fully as possible. Compare the reac- tion times with those of previous experiments. Take at least 100 records. What can you say of the relative size of the mean variation md the number of premature reactions? 142 PSYCHOLOGICAL EXPERIMENTS Materials — Chronoscope. with accessories for auditory stimuli. 128. Visual Natural Reactions Take 100 reactions to a visual stimulus as- suming the natural attentive attitude. Care must be taken to make the appearance of this stimulus noiseless, because auditory reactions are usually faster than visual. The subject, if he heard any sound, would react to it rather than to the visual stimulus. Materials — Chronoscope, with accessories for visual stimuli. 129. Visual Sensory Reactions Record 100 reactions to a visual stimulus with the sensory attentive attitude. Materials — Chronoscope, with accessories for visual stimuli. 130. Visual Motor Reactions Record 100 reaction-times to a visual stim- ulus with the motor attentive attitude. Materials — Chronoscope, with accessories for visual stimuli. 131. Tactual Reactions, Normal Records can also be made of reaction times to tactual stimuli. Here also care must be taken REACTION TIME EXPERIMENTS 143 to avoid any auditory stimulation. The three different attentive attitudes can be repeated for this stimulus. Record 100 natural tactual reactions. Materials — Chronoscope, with accessories for tactual stimuli. 132. Tactual Senory Reactions React 100 times to a tactual stimulus taking on the sensory attentive attitude. Materials — Chronoscope and accessories for tactual stimuli. 133. Tactual Motor Reactions Record 100 reaction-times to a tactual stim- ulus with the motor attentive attitude. Materials — Chronoscope with accessories for tactual stimuli. 134. Discrimination Time Arrange a screen or revolving mirror in connection with the chronoscope so that when a sheet of paper is exposed to view, the chronoscope will be started. Install two recording keys, one for the light hand, the other for the left. Expose two colors of papers, one at a time, in irregular order. The observer must always react with one hand for one color and the other hand for the other color. Take 100 reactions in which 144 PSYCHOLOGICAL EXPERIMENTS there has been a discrimination of two colors. Compare the time with that of the simple re- actions. This experiment can be continued by introducing more keys and colors. Materials — Chronoscope with accessories for exposing colored paper and additional re- action key. 135. Discrimination Time Repeat the former experiment with the two shades of grey that differ very little or with tints and shades of the same color. What is the relation of the ease of discrimination to dr- crimination time? Materials — Chronoscope with the same ac- cessories as in the former experiment, greys. 136. Recognition Time An exposure screen is arranged as in the Discrimination Experiment. On this screen ex- pose words, letters, pictures or other material for which you wish to measure the recognition time. For the reacting key a sound key may be used which records the word when spoken. The word may be spoken by the observer and the experimenter can react with the ordinary touch key, allowing the spoken word to be the auditory stimulus for a simple auditory reac- tion. The total time then would be the observ- er's recognition time plus the experimenter's RE ACTION TIME EX PERIMENTS' 14S simple auditory reaction time. The average auditory reaction time can be subtracted from the total average leaving the average recogni- tion time. No less than 100 records should be taken. Materials — Chronoscope with accessories for exposing words, etc. 137. Free Association Time Arrange the apparatus in the same way as for recognition time. Present words and instead of pronouncing the word itself speak the first word that comes to your mind after the word shown on the screen. Record the stim- ulus word, the associated word and the associa- tion time. After having the record for 50 or 100 associations classify them into associations of meaning — coordination, e. g baby-infant super ordination Nile-river sub ordination lake-Ontario part-whole collar-coat whole-part wagon-wheel sound associations — letters or parts of words. . .fool-foolish rhyme cat-rat associations of cause fire-heat serial associations three-four associations of contiguity in space, .locomotive car. 146 PSYCHOLOGICAL EXPERIMENTS The classifications given are not exhaustive but are merely suggestive. Add any that may be needed in your series. Materials — Chronoscope with accessories for exposing words, etc., word lists. 138. Controlled Associations With the same apparatus as in the former experiment for the free associations the time for naming the opposites, part-whole, whole- part, etc., can be measured. In any of these series the material must be prepared for the kind of control that has been agreed upon. The controlled associations times are often so long that they can be measured with sufficient accuracy by means of a stop watch. Materials — Chronoscope or stop watch with word exposure apparatus, word lists. 139. Judgment Time With the same apparatus as in experiment No. 136, ask the observer questions on the ex- posure screen which require judgment for their answers, viz: Which is the larger lake (this can be given orally) Michigan or Superior (on the exposure screen) ? Record the questions and replies. Full introspective reports will be especially valuable. Materials — Chronoscope with accessories for exposing words, etc. REACTION TIME EXPERIMENTS 147 140. Attention Fluctuations Set the reaction apparatus up for auditory reactions. (Visual and tactual can also be used.) Time the interval between the "ready" signal and the stimulus for reacting by means of a stop watch. Vary the interval from 1 to 10 seconds, recording the interval and the reaction time. Take at least 10 reactions for each re- spective second's interval from 1 to 10 seconds. Mix the order in which the various intervals are given so the subject does not know how long he will have to wait after the "ready" signal is given until the reacting stimulus will appear. Record the reactions for each second's interval in the same column. Average the ten reactions for which there was a wait of one second, those for which there was a wait of two seconds, three seconds, etc. The "ready" sig- nal is for the purpose of concentrating the at- tention of the subject. The averages then show the fluctuations that occur for various intervals. What interval, in your case, was the most favorable for quick reactions? Are there regular rhythmic fluctuations of the attention? How do your fluctuations correspond with those of others? Materials — Chronoscope with its various ac- cessories, stop watch. 148 PSYCHOLOGICAL EXPERIMENTS 141. Intensity of Stimulus and Reaction Time, Auditory Vary the intensity of the auditory stimulus and record 100 reactions for each respective intensity. What effect does intensity of stim- ulus have on the reaction time? Do the same proportional differences exist for extreme stimulations? Do the differences occur for all kinds of reaction movements? Materials — Chronoscope and accessories. 142. Intensity cf Stimulus and Reaction Time, Visual Perform this experiment in the same man- ner as the former one, except that a visual stimulus is used instead of an auditory stimulus. Materials — Chronoscope and accessories. 143. Intensity of Stimulus and Reaction Time, Tactual Perform this experiment in the same man- ner as the two former ones, using a tactual stimulus instead of the auditory and visual stimuli. Materials — Chronoscope and accessories. NOTES 149 ISO PSYCHOLOGICAL EXPfiRIMENTS CHAPTER 15. Judgment 144. Weber's Law for Lifted Weights Make a series of weights so their external appearance is just the same. Have the stand- ard 100 grams, then have a series running 101, 102, 103, 104, 105, 106, 107, 108, 109, 110 grams. Begin with the weights weighing 100 and 101 grams. " Present the standard then the 101 grams weight or the heavier and the standard in promiscuous order. Have the subject report each time as to the relative weight (lighter or heavier) of the first weight presented. Repeat this until 100 judgments have been made for the first pair of weights. Repeat the experi- ment with 100 and 102 grams, 100 and 103 grams, etc., until no errors are made. Repeat the whole experiment using 500, 505, 510, 515, etc., gram weights. Repeat the experiment with 1,000, 1,020, 1,030, 1,040, etc., gram weights. Given that any weight must be increased by 1-n of itself to be felt as distinctly heavier, from your data calculate the value of n. Will this hold true for very heavy or very light weights? Materials— Weights. 152 PSYCHOL OGICAL EXPERIMENTS 145. Weber's Law for the Felt Length of Lines Use the edge of a card 5 cm. as a standard by pressing it on the skin. Use cards slightly wider and wider until no errors are made in judging one wider than the standard. Repeat the experiment using a standard line of 10 cm. In the same manner as described for the Weber law in lifted weights calculate the constant for the tactual judgment of the length of a line. Materials — Cards. 146. Judgment of Distance Present a standard line 10 cm. long and ask the subject to draw a line just as long as the standard, on a sheet of paper lying beside it. Cover the line already drawn and repeat the drawing until 100 judgments have been made. Repeat the experiment with standard lines 20 and 30 cm. long. Measure the reproductions carefully and calculate the per cent of error for each standard. Is the error a constant frac- tional part of the standard line? Be careful to avoid any artificial means of measuring the line either conscious of uncon- scious. Materials— Standard lines. NOTES 153 154 PSYCHOLOGICAL EXPERIMENTS CHAPTER 16. Imagination and Intelligence 147. Mental Imagery Galton studied mental imagery by means of questionairre the essentials of which are re- produced here, Think of your breakfast table as you sat down to it this morning; call up the a,ppearance of the table, the dishes, the food, th,e persons present, etc. Then write answers to the following ques- tions: 1. Are the outlines of the objects distinct and sharp? 2. Are the colors bright and natural? 3. Where does the image seem to be situated? In the head? Before the eyes? At a dis- tance? 4. How does the size of the image compare with the actual size of the scene? 1. Can you call to mind better the face or voice of a friend? 2. When violin is suggested, do you first think of the appearance of the instrument or the sound when it is played? 156 PSYCHOLOGICAL EXPERIMENTS 3. (a) Can you call to mind natural scenery so that it gives you pleasure? (b) Music? (c) The taste of fruit? 4. Have you ever mistaken an hallucination for a perception, e. g. apparently heard a voice or seen figure when none was present? Describe the experience. From your above answers discuss your imagery as fully as pos- sible. 148. Illusory Warmth Make a box with a small flue on top and a hole in the side for the insertion of the subject's finger. Have a door arranged away from the subject through which an alcohol lamp can be placed in the box. Announce to the subject that you want to test his sensitivity to warmth and have him place his finger in the hole. Tell him to report when he begins to feel the warmth, as- suring him that arrangements are such that it will not burn him. Just as the alcohol lamp is placed in the box extinguish the flame noise- lessly, by placing the cap on. Note the time that elapses until warmth is reported. Study several individuals for comparative data. Materials — Special box, alcohol lamp. 149. Completion or Filling in Tests The Completion Tests are said to be ex- IMAGINATION AND INTELLIGENCE 157 cellent tests for retention, readiness of recall, quick and accurate association, creative imag- ination, in short, splendid tests for intelligence. Various materials may be used such as words in which letters have been omitted, words with syllables omitted, sentences with words omitted or paragraphs with phrases omitted. Prepare material for the test leaving blanks for the mat- ter to be filled in. See that the subject clearly understands what is to be done. Keep the time accurately with a stop watch. Either record the time required to complete the task or limit the time and note the amount of work accom- plished. Compare your results with those of other subjects. Note the attitude of the sub- ject. Does he hesitate? Is he attentive? Does he get the meaning of the material presented? Materials — Special blanks, stop watch. 150. Imagination and Invention Prepare a series of ink blots that from their grotesque form will likely suggest pictures. Tell the subject the nature of the material and that they are not real pictures but for him to leisurely examine them and tell you what objects they suggest to him. Take the blots up one at a time and allow say three minutes ex- amination of each. Treat the data by comparing the total num- ber of associations with that of others. 158 PSYCHOLOGICAL EXPERIMENTS Materials — Ink blots. 151. Vocabulary Test Select a series of 100 words covering the range of the field of information with which the subject should be familiar. Ask him to con- sider each one carefully and place after it a mark to indicate, — 1. If he could define it exactly. 2. If he could define it well enough so as to give an idea of its meaning without its necessarily satisfying an expert. 3. If he is only roughly familiar with the word, has an indefinite idea of meaning. 4. If the word is new and unknown. The following is a list suggested by Whipple:— ageratum Braille amphioxus call-loan amphora calorie annealed cantilever Anthony Wayne Caedmon apocalypse catalepsy architrave Cephalic index audjourdhui ceramics Babcock test chamfer base-hit Chartism Bernard Shaw chlorine Bokhara chromosome IMAGINATION AND INTELLIGENCE 159 clearing-house Les Miserables cleistogamous linotype cosmogony logos cotangent luff dibble Malthus' law dietetics metacarpal dryad midiron electrolysis Millet Elohim mitosis entree morgen Eocene nada Euclid natural selection f-64 noi f. 0. b. ohm gambit parallax gasket peneplain glycogen Pestalozzi gneiss Polonius golden section pomology guimpe puer hedonism pyramidal tract hemiptera quadratics homiletics rococo hydraulic press R. S. V. P. impetigo scherzo impressionism semaphore infusoria simony intaglio spoils system - Kepler's law Stoicism kilogram synecdoche kinesthetic testudo kinetic tort 160 PSYCHOLOGICAL EXPERIMENTS trephine triangulation trilobite triple-expansion undistributed middle Utopia vantage-in way-bill Weismannism wigwag X-Ray Zionism Ask the subject to define all that have been marked in class of "roughly familiar." "Make tables in which the results are compared with those of other subjects. For those whose information is somewhat limited a much easier list will be necessary. An opposites test in which the subject is called upon to give exact opposites will also give con- siderable information, as to the extent of the vocabulary. An account of the papers, magazines, books and environment with which the subject is acquainted will give an idea of the expected size of his vocabulary. An interesting, exercise will be the arrang- ing of a list suitable for various intelligence ages. NOTES 161 162 PSYCHOLOGICAL EXPERIMENTS CHAPTER 17. Memory 152. Economy in Memorizing Select two pieces of literature of about equal difficulty such as two stanzas from the same poem. Memorize one selection by dividing into such parts as seem convenient. Memorize the first division, repeat it and add the next divi- sion. Continue this process until the selection is finally memorized. Record the number of minutes required. Consider it memorized as soon as you are able to repeat it correctly with- out looking, at the book. Work as intently as possible and disregard any prejudice you may have in favor of either method. After a brief rest period, memorize the. sec- ond selection by reading it entirely through each time. Concentrate as strongly as you did on the first. Note the time as before. How do the two methods compare? A few hours later or a day later repeat the experiment with the same material to see if either method is better for final learning. Materials — Poetry. 153. Measurement of Memory Prepare a series of twelve nonsense sylla- bles. These syllables are prepared by inserting 164 PSYCHOLOGICAL EXPERIMENTS a vowel between two consonants, rejecting all those forming known words. Start a metronome to beating 60 times a minute. At each beat read one of the syllables going through the series. Count each time you read the series through on your fingers or by dropping a card. At the first correct repro- duction of the series the experiment is stopped and the number of repetitions required to learn the series recorded. Numbers and letters can be used for this ex- periment. After a given interval, say one hour, the series is relearned. The saving in the number of repetitions is noted. Materials — Nonsense syllables, metronome. 154. Memory of Auditory Images Prepare a series of cards by pasting (gummed numbers) one of the digits on each card. Use all the digits 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, which will give you ten cards. The digits should be large enough so they can easily be read. Set a metronome so that it beats one stroke per second. The experimenter should shuffle his cards and arrange them so that there are not more than two numbers that appear in their regular consecutive order. Then take the cards and read one after each beat of the metro- MEMORY 165 nome in a clear distinct uniform tone of voice. The observer listens until the experimenter is through with the series then writes the series on a sheet of paper. The records are preserved and compared with the original series. Omis- sions, deviations and insertions are counted and stand as the observer's errors. Deviations can be scored by counting the least number of steps that the number would have to be moved to put it in its proper place. It is well to ask the subject to close his lips firmly and place his tongue against the roof of his mouth to avoid the temptation to speak the numbers. Materials — Cards with numbers, letters or nonsense syllables. 155. Memory for Various Forms of Images Present the series in the same manner as in the former experiment, but have the sub- ject write each number on a slip of paper in addition to speaking it aloud. Discard the paper and reproduce the series on another sheet. At least ten trials should be made for all the digit memory series. Occasionally subjects will be able to remem- ber all 10 of the digits in these experiments. It will be necessary to introduce part of a sec- ond set of cards, taking care not to repeat the same number twice in presenting them. This series of experiments can be repeated 166 PS YCHOLOGICAL EXPERIMENTS using letters or nonsense syllables instead of numbers. Special apparatus is often found in labora- tories for making the exposure of the memory- material easy and more accurate. Materials — Nonsense syllables, numbers, letters, metronome. 156. Memory for Various Forms of Images Present the cards as in the former experi- ments, having the subject pronounce the num- bers aloud as the card is laid down, in concert with the experimenter. Materials — Cards with numbers, letters, nonsense syllables. 157. Memory of Visual Images Use the same cards as were used for the Memory of Auditory Images. Instead of read- ing them to the subject, lay the cards down be- fore him at the rate of one a second and have him write the series after they have all been thus presented. Lay the cards on top of each other and remove the series when the last card has been exposed 1 second. Materials — Cards with numbers, letters, nonsense syllables. 158. Memory of a Series Get a series of photographs (people un- MEMORY 167 known to the observer) of the same size with the name on the back of the photo. Learn the name of one so the photo can be identified with- out reference to the name on the back. Add another, naming both. In a like manner learn to identify a third, always going over, the series already learned. After once having learned to identify one never refer to the back of the card again. Mix the order in which the photos are f resented always adding a new one to the series, he task of remembering the faces will seem easy for a time. After the series becomes longer some of those learned first will probably be for- gotten. Give an explanation of your results. Materials — A series of photographs., 159. Fidelity of Report Tests designed to check the memory and imagination of the subject consists in present- ing some series of objects or scene to him and by a carefully prepared list of questions note the amount and accuracy of the reproduction of the original scene or presentation. The pres- entation must be uniform and for a given time. Pictures are presented about one minute apart, although they may be shown as short a time as 5 seconds or as long as 7 minutes. A slightly modified form of Binet's card of objects con- sists of a sheet of orange yellow cardboard 35x 40 cm. upon which have been fastened two photographs, a label, a button, a penny and a 168 PSYCHOLOGICAL EXPERIMENTS postage stamp. Simply state to the subject that you want to see how good his memory is. Let him look at the card 40 seconds, telling him to study it carefully as you will later inquire about all the little details. After the subject has looked at the card ask him to answer as accurately as possible the fol- lowing list of questions: 1. Did you notice a coin? 2. What was its denomination ? 3. Did it show 'heads' or 'tails'? 4. Was it bright or dull? 5. Was it new or worn? 6. Did you see a button ? 7. What was its shape and color? 8. What material was it made of? 9. How many holes were there in it? 10. How was it fastened to the cardboard? 1 1 . Did you see the small picture near the top ? 12. What color was it? 13. What did the picture represent? 14. What was its shape? 15. How many persons were in it? 16. What was the lady doing with her right hand? 17. What was the other person doing? 18. Is the title of the picture printed on it? 19. What is the man looking at? 20. What was the facial expression of the man? 21. Was there another picture? Where? MEMORY 169 22. What was its shape? 23. How many persons were there in it? 24. How many animals are shown? 25. Is any part of any of the animals cut off by the margin of the picture? 26. Are there any words printed on this pic- ture? What are they? 27. How are the people dressed? 28. What was in the foreground? 29. What was in the background? 30. At what season of the year was the pic- ture taken? Why? 31. Did you see a postage stamp? 32. Was it American or Foreign ? 33. What was its value? (denomination) 34. What color was it? 35. Was it new or had it been used? 36. Did you see a label? 37. What color was it? 38. What shape was it and approximately what size? 39. Was there any printing on it? Where? What? 40. Was there a border around the printing^ 41. How were the various objects fastened to the cardboard? 42. What was the shape of the cardboard? 43. Was there anv printing or writing on the cardboard? What? 44. What was the largest object fastened to the cardboard? 170 PSYCHOLOGICAL EXPERIMENTS 45. Did the cardboard rest on its narrow or wide side? 46. What object was nearest the edge of the cardboard? 47. What object did you notice first? 48. How were the various objects placed on the cardboard? Right side up or slanting or how? 49. Was there any frame around the card- board? 50. What was the color of the cardboard? The questions have been arranged in groups of five for each for ease in grading. The ques- tions are suggestive only and must be adapted to the particular objects mounted on your card of objects. 160. Fidelity of Report of an Incident Arrange a performance such as a quarrel, a fight, a class disturbance, etc., in which the objects and words used have been carefully pre- arranged. Let the incident come as a surprise to a group and after some time elapses ask a series of questions concerning the details of the affair. The influence of suggestion may be studied by introducing questions concerning objects that really were not there, viz: — remove all erasers before the performance and let one uf the questions be, How many erasers were at the black board? ■MEMORY 171 These experiments have a direct bearing on the errors in evidence, reports, discrimination, etc. Modifications can be made and scenes se- lected illustrating many different incidents. 172 PSYCHOLOGICAL EXPERIMENTS CHAPTER 18. Affective Consciousness 161. Mental Analysis by the Association Time Method Have two boxes just alike on the outside. In one of them place a bottle plainly labeled "Whisky" and a revolver. In the other box place a doll, a marble, a top and a jack-knife. Have these boxes placed in another room and ask the subject to look at the contents of only one of the boxes. It now becomes the problem of the experimenter to find out which box the subject opened. Make a list of 50 words to be used as stimulus words for free associations. In this list of 50 words have 10 that are closely related to the contents of the one box and 10 that are closely related to the contents of the other box. The remaining words should be irrelevant and just as well known as the related words. The subject should have no previous knowledge of the words to be given, but should be told to avoid words that would reveal his knowledge of either box. He should face the experimenter and give as quickly as possible the idea brought up by the stimulus word. Keep a record of the stimulus word, asso- ciated word and association time. Average tht; time for the 30 unrelated words, the 10 words referring to the one box and the 10 referring to 174 PSYCHOLOGICAL EXPERIMENTS the other. The words referring to the box seen will probably have a much longer average asso- ciation time. Invent other problems to which this experiment can apply. The association times will be long enough to be measured by a stop watch if the more complicated apparatus is not available. Materials — Boxes arranged as indicated in the experiment, stop watch. 162. Affective Consciousness, Comparative Method Make a screen of dull grey color about 40 cm. square. Have two openings 10 cm. square placed near the center of the screen about 5 cm. apart. In these windows display colors compar- ing them with each other as to agreeableness. Compare ten colors with each of the other colors and make a table of results: Pink Red Orange Yellow Blue Purple Violet Pink Red Orange Yellow Green Mark the more agreeable + and the less agreeable — . Let the vertical column represent the color compared with the standard in the hor- izontal column. Add the plus signs horizontally and the minus signs vertically. The sum of AFFECTIVE CONSCIOUSNESS ITS these two signs for any color will show the num- ber of judgments in favor of that color. From the number of judgments obtained in favor of the colors make out the order of preference. Materials — Grey screen, colored papers. 163. Affective Consciousness, Order of Merit Method Take a series of ten picture post-cards rep- resenting landscape views. Ask some one to arrange them in order from the most beautiful to the one that seems least beautiful. Mark these cards with the letters A, B, C, D, E, F, G, H, I, J. Assign to the card selected as the most beautiful the highest number of the series, 10. The next one in order, 9; the least beautiful one would then be represented by 1 ; placing num- bers under the respective letters representing the cards. Have at least ten different individuals classify the series recording the judgments. Average the judgments for each picture and find the mean variation. The highest average will represent the highest grade. A small mean variation will indicate a considerable agreement on the part of the subjects, while a large mean variation will show much disagreement. Re- ports of the opinions of the observers should reveal the reasons for the various judgments. This method is splendid for finding the rela- tive merit of hand-writing, advertisements, etc. 176 PSYCHOLOGICAL EXPERIMENTS The reverse order of assigning values can also be used i.e. mark the highest rank 1 ; sec- ond in rank 2, and the poorest one the highest number in the series. This system, however, becomes awkward when the permanence of im- pression is to be measured by this method, for, some of the series will be entirely forgotten and a value will be hard to assign. With the method indicated above such a value becomes and is averaged just the same as the other judgments. This method can be modified to meet various experimental problems. Materials — Landscape views, advertise- ments, samples of handwriting, etc. 164. Aesthetic Division of a Line Cut a strip of black paper 102.5 cm. long, 2..5 cm. wide and mount it on a white background. Take a strip of white paper 2.5 cm. wide and lay it across the line in such a manner as to divide the black line into two parts. Move the white line back and forth until the proportions of the two parts are most pleasing. Record the divi- sions made by a number of people and average the results. Reduce the proportions to as sim- ple a fraction as possible. This experiment can also be used in the determination of the most pleasing proportions for an oblong, oval, etc. Materials — A line or figure the proportions or shape of which can readily be changed. AFFECTIVE CONSCIOUSNESS 177 165. Pneumograph Records A pneumograph is placed upon the observer in such a manner as not to be obstructed by the clothing, back of the chair, or pressure against the table. The pneumograph is connected with 1 recording tambour which writes upon the smoked paper on a revolving kymograph drum. A time line showing seconds or fifths of a sec- ond should be traced simultaneously. After having adjusted the apparatus so as to make a good record, allow the subject to take on a nor- mal resting attitude and get a pneumograph record. Then have the observer grip very hard, rest, read, rest, listen to a funny story, rest, smell of agreeable and disagreeable odors, etc. What fluctuations of breathing take place? Invent other conditions that will bring on vari- ous states of affective consciousness. Materials— Pneumograph, tambour, kymo- graph, time marker, stories, problems, odors. 1B6. Plethysmographic Records Repeat the former experiment substituting for the breathing tracing the tracing of the pulse. Then take both a breathing and a pulse tracing. Good circulation records are some- what harder to get and great care must be tak- en to have all adjustments perfectly made. Materials— Plethysmograph, recording tam- bour, kymograph, time marker. 178 PSYCHOL OGICAL EXPERIMENTS 167. Feeling and Unconscious Movement The automatograph or swinging planchette consists of a wooden platform upon which the arm and hand can easily be rested. This plat- form is suspended from the ceiling. At the end on which the hand rests a stylus is inserted which writes on the glazed surface of a smoked Fig. 51. Swinging Planchette. sheet of paper lying beneath on a table. The paper has to be moved after each experiment The subject keeps his eyes closed throughout the experiments. At first a dreamy indifferent at- titude should be taken by the observer, then various odors can be silently brought under the subject's nostrils. Some of these odors should be pleasant, others unpleasant, and the effect of each noted. Continue this experiment by describing journeys, etc., to the subject and see AFFECTIVE CONSCIOUSNESS 179 if his hand involuntarily follows the direction you give. Notice the effect of watching a slow- ly swinging pendulum, rhythmic music, etc. Materials — Swinging planchette, glazed pa- per, odors, pendulum. 168. Electrical Conductivity of the Body It is a well known fact that the human body has a rather high resistance to the conduction of electricity. Some experiments seem to show that this resistance varies under different emo- tional attitudes. Connect a sensitive gal- vanometer and a weak dry cell in series. Lay zinc plates on the ends of the two wires. Lay the plate on the table or on the arms of a chair. The subject seats himself comfortably and sits very still. Place the hands on the plates tak- ing care to hold them in the same positions. In the form of words, phrases, or questions, ask the subject to report his free associations. Give words to which the subject would be emotion- ally indifferent. Mix with them words that will likely stir up some emotional reactions. Record the galvanomic deflections for all the associations comparing the magnitude of the deflections for the indifferent associations with those accompanied by considerable emotion. Materials — ^Galvanometer, dry cells, zinc plates. 180 PSYCHOLOGICAL EXPERIMENTS NOTES 181 182 PSYCHOLOGICAL EXPERIMENTS Materials used in the Psychological Experi- ments. Numbers refer to the experiments. Acoumeter, 41. Advertisements, 163. Alcohol lamp, 148, Algometer, 19. Atomizer, 92. Boxes (different sizes of the same shape), 93. Brass plate with standard holes, 89. Brass strips, 90. Brightness discrimination apparatus, 61. Bristles, 8. Bulbs (rubber), 119, 120. Bunsen burner, 7, 11, 13. Camel's hair brushes (pointed), 28, 30. Campimeter, 64, 65. Camphor gum, 34. Candles, 57. Cardboard, 21 (grey), 63, 68, 78, 79, 81, 82, 83, 162. Chronoscope and accessories, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142. Cocaine, 30. Coin, 12. Colored papers, 67, 68, 76, 81, 82, 83, 134, 162. Compass, 20, 22, 23, 24. Corks (large), 102. 184 PSYCHOLOGICAL EXPERIMENTS Cotton (absorbent), 26, 27. Counter (electric), 84, 89. Cylinder (metallic, pointed), 6, 7, 13. Dark room, 57, 59. Deep vessel, 14. Discs (paper, colored, black, white, grey), 66,, 67, 69, 70, 71, 72, 73, 74, 75, 76, 77. Dissecting instruments, 3, 4, 5. Drawing instruments, 102. Dyes, 6, 7, 8, 9, 10. Dynamometer (hand), 86. Electric batteries (dry cells), 84, 89, 90. Electric current (interrupted), 87. Electric sounder, 90. Ergograph, 94, 95, 96. Ether, 92. Exposure apparatus, 106, 107, 108, 109, 110, 115., Eye-glasses (special stereoscopic), 104. Feit, 91, 92. Galton-Edlemann whistle, 53. Galvanometer, 168. Glass (colored and plain), 79. Globe, 102. Hairs, 8. Heads of animals, 3. Hinged board, 85. Holmgreen worsteds, 63. Graduated glasses, 27, 28, 29, 34. LIST OF MATERIALS 185 Ice, 6, 7, 13. Ink-blots, 150. Kymograph, 119, 120, 121, 165, 166. Lens (double convex), 57. Letters (pied), 116. Marble dust, 26, 27. Marbles, 97. Masson disc, 1 19. Measuring disc (graduated in per cents), 66, 67, 69,70,71,72,73,74,75,76,77. Metal plate, 84. Metal rod, 84, 89. Metronome, 94, 96, 99, 121, 122, 123, 124, 153, 154, 155, 156, 157. Millimeter scale, 20, 21. Mirror, 98, 1 13. Musical instruments, 46, 49. Odors, 35, 36, 37. Paper discs, 167. Pendulum, 167. Perimeter, 64, 65. Pictures (special), 104. Pipettes, 32. Photographs, 158. Photometer, 59. Planchette, 167. Plethysmograph, 166. Pneumograph, 165. 186 PSYCHOLOGICAL EXPERI MENTS Pressure scale, pressure pain balance, 19. Protractor, 85. Puzzle pictures, 101. Quinine, 27, 28, 29, 30, 31, 33. Recorder (electric), 121. Resonaters, 44, 49. Rotator, 62, 66, 67, 69, 70, 71, 72, 73, 74, 75, 76, 77, 119. Rotating platform, 38, 39, 40. Rubber tube, 42, 46. Salt, 26, 27, 28, 29, 30, 31, 32, 33. Sand, 93. Scale, 8, 27, 28. Sheep heads, 4. Skulls, 1. Sonometer, 48. Spinal cord (specimens of), 5. Star (outlines of six pointed), 98. Sterescope, 102, 103, 105. Sterescopic slides (special), 103 , (general), 105. Sugar, 26, 27, 28, 29, 30, 31, 32, 33. Tambour, 119, 120, 165, 166. Tape measure, 41. Target, 97. Tartaric acid, 28, 29, 30, 31, 33. Telegraph key, 121. Time marker, 119, 120, 121, 165, 166. Thermometer, 11, 18. LIST OF MATERIALS 187 Thorns, 9, 10. Tissue paper, 76. Tracing paper, 6, 7, 8, 9, 10. Tooth-picks, 6, 7, 8, 9, 10, 13. Tuning forks, 42, 43, 44, 45, 46, 47, 50, 51, 52, 55, 56. Watch, 12, 41, 57. Wax, 8. Vertebrae, 2. Vinegar, 33. Vision test charts, 60. Weights, 88, 91, 92, 144. General Supplies. Alcohol, carbon paper, cards, clamps, electric current, ink, formalin, matches, millimeter, centimeter and meter measures, pans, paper (blank, cross-section, kymograph glazed), pen- cils, pens, pins, rods, screws, nails, tacks, etc.; stop-watch, tape-measures, thread, cord, tools (general metal and wood working), wire (bind- ing and electric conduction), etc., etc. iipwlihiitw' uC, '-