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[Transcriber's notes] This text is derived from an unedited version in the Internet Archive.
Page numbers are indicated by numbers enclosed in curly braces, e.g. {99}. They have been located where page breaks occurred in the original book.
Labels and text in a figure that are not mentioned in the figure description are included as a comma separated list, as in "(Figure text: cochlea, vestibule, 3 Canals)".
Lengthy footnotes and quotations are indented.
Obvious misspellings and typos are corrected but inconsistent spelling is not resolved, as in coordinate and cooerdinate.
Here are the definitions of some unfamiliar words (to me).
amour propre self-esteem; self-respect.
esprit de corps camaraderie, bonding, solidarity, fellowship.
motility (motile) moving or capable of moving spontaneously.
unwonted unusual. [End Transcribers's notes]
PSYCHOLOGY A STUDY OF MENTAL LIFE
BY ROBERT S. WOODWORTH, Ph. D. Professor of Psychology in Columbia University
NEW YORK HENRY HOLT AND COMPANY 1921
COPYRIGHT, 1921 BY HENRY HOLT AND COMPANY
Printed in the U.S.A.
PREFACE
A few words to the reader are in order. In the first place, something like an apology is due for the free way in which the author has drawn upon the original work of many fellow-psychologists, without any mention of their names. This is practically unavoidable in a book intended for the beginner, but the reader may well be informed of the fact, and cautioned not to credit the content of the book to the writer of it. The author's task has been that of selecting from the large mass of psychological information now available, much of it new, whatever seemed most suitable for introducing the subject to the reader. The book aims to represent the present state of a very active science.
Should the book appear unduly long in prospect, the longest and most detailed chapter, that on Sensation, might perfectly well be omitted, on the first reading, without appreciably disturbing the continuity of the rest.
On the other hand should any reader desire to make this text the basis of a more extensive course of reading, the lists of references appended to the several chapters will prove of service. The books and articles there cited will be found interesting and not too technical in style.
Much advantage can be derived from the use of the "Exercises". The text, at the best, but provides raw material. Each student's finished product must be of his own making. The exercises afford opportunity for the student to work over the material and make it his own.
A first or preliminary edition of this book, in mimeographed sheets, was in use for two years in introductory classes conducted by the author and his colleagues, and was subjected to exceedingly helpful criticism from both teachers and students. The revision of that earlier edition into the present form has been very much of a cooeperative enterprise, and so many have cooeperated that room could scarcely be found for all their names. Professor A. T. Poffenberger, Dr. Clara F. Chassell, Dr. Georgina I. Gates, Mr. Gardner Murphy, Mr. Harold E. Jones and Mr. Paul S. Achilles have given me the advantage of their class-room experience with the mimeographed book. Dr. Christine Ladd-Franklin has very carefully gone over with me the passages dealing with color vision and with reasoning. Miss Elizabeth T. Sullivan, Miss Anna B. Copeland, Miss Helen Harper and Dr. A. H. Martin have been of great assistance in the final stages of the work. Important suggestions have come also from several other universities, where the mimeographed book was inspected.
R. S. W. Columbia University August, 1921
CONTENTS
CHAPTER I
PAGE
WHAT PSYCHOLOGY IS AND DOES 1
Varieties of Psychology 2
Psychology as Related to Other Sciences 5
The Science of Consciousness 7
The Science of Behavior 8
Introspection 10
Objective Observation 11
General Lines of Psychological Investigation 14
Summary and Attempt at a Definition 17
Exercises 19
References 20
CHAPTER II
REACTIONS 21
The Reaction Time Experiment 22
Reflex Action 24
The Nerves in Reflex Action 26
Internal Construction of the Nerves and Nerve Centers 31
The Synapse 34
Cooerdination 37
Reactions in General 39
Exercises 42
References 44
CHAPTER III
REACTIONS OF DIFFERENT LEVELS 45
Different Sorts of Stimuli 47
The Motor Centers, Lower and Higher 49
How the Brain Produces Muscular Movements 53
Facilitation and Inhibition 54
Super-motor Centers in the Cortex 56
Speech Centers 57
The Auditory Centers 59
The Visual Centers 62
Cortical Centers for the Other Senses 68
Lower Sensory Centers 64
The Cerebellum 66
Different Levels of Reaction 65
Exercises 67
References 67
CHAPTER IV
TENDENCIES TO REACTION 68
Purposive Behavior 70
Organic States that Influence Behavior 72
Preparation for Action 74
Preparatory Reactions 77
What the Preparatory Reactions Accomplish 79
What a Tendency Is, in Terms of Nerve Action 82
Motives 84
Exercises 86
References 88
CHAPTER V
NATIVE AND ACQUIRED TRAITS 89
The Source of Native Traits 90
Reactions Appearing at Birth Must Be Native 91
Reactions That Cannot Be Learned Must Be Native 92
Experimental Detection of Native Reactions 93
Is Walking Native or Acquired? 95
Universality as a Criterion of Native Reactions 97
Some Native Traits Are Far from Being Universal 98
Why Acquired Traits Differ from One Individual to Another 99
What Mental Traits Are Native? 100
Exercises 103
References 104
CHAPTER VI
INSTINCT 105
The Difference Between an Instinct and a Reflex 107
An Instinct Is a Native Reaction-Tendency 109
Fully and Partially Organized Instincts 111
Instincts Are Not Ancestral Habits 113
Instincts Not Necessarily Useful in the Struggle for Existence 114
The So-called Instincts of Self-preservation and of Reproduction 115
Exercises 117
References 117
CHAPTER VII
EMOTION 118
Organic States That Are Not Usually Classed as Emotions 119
How These Organic States Differ from Regular Emotions 120
The Organic State in Anger 121
Glandular Responses During Emotion 122
The Nerves Concerned in Internal Emotional Response 124
The Emotional State as a Preparatory Reaction 125
"Expressive Movements," Another Sort of Preparatory Reactions 126
Do Sensations of These Various Preparatory Reactions Constitute the Conscious State of Emotion? 128
The James-Lange Theory of the Emotions 129
Emotion and Impulse 130
Emotion Sometimes Generates Impulse 132
Emotion and Instinct 134
The Higher Emotions 136
Exercises 136
References 136
CHAPTER VIII
INVENTORY OF HUMAN INSTINCTS AND PRIMARY EMOTIONS 137
Classification 138
Responses to Organic Needs 139
Instinctive Responses to Other Persons 145
The Play Instincts 151
Exercises 170
References 171
CHAPTER IX
THE FEELINGS 172
Pleasantness and Unpleasantness Are Simple Feelings 173
Felling-tone of Sensations 174
Theories of Feeling 175
Sources of Pleasantness and Unpleasantness 178
Primary Likes and Dislikes 180
Other Proposed Elementary Feelings 184
Exercises 186
References 186
CHAPTER X
SENSATION 187
The Sense Organs 188
Analysis of Sensations 197
The Skin Senses 197
The Sense of Taste 201
The Sense of Smell 203
Organic Sensations 204
The Sense of Sight 204
Simpler Forms of the Color Sense 209
Visual Sensations as Related to the Stimulus 212
Color Mixing 214
What Are the Elementary Visual Sensations? 216
Theories of Color Vision 220
Adaptation 224
Rod and Cone Vision 226
After-images 226
Contrast 227
The Sense of Hearing 228
Comparison of Sight and Hearing 231
Theory of Hearing 234
Senses of Bodily Movement 236
Exercises 241
References 243
CHAPTER XI
ATTENTION 244
The Stimulus, or What Attracts Attention 245
The Motor Reaction in Attention 248
The Shifting of Attention 251
Laws of Attention and Laws of Reaction in General 256
Sustained Attention 257
Distraction 259
Doing Two Things at Once 260
The Span of Attention 261
Summary of the Laws of Attention 262
Attention and Degree of Consciousness 265
The Management of Attention 267
Theory of Attention 268
Exercises 270
References 270
CHAPTER XII
INTELLIGENCE 271
Intelligence Tests 272
Performance Tests 275
Group Testing 276
Some Results of the Intelligence Tests 278
Limitations of the Intelligence Tests 281
The Correlation of Abilities 288
General Factors in Intelligence 285
Special Aptitudes 288
Heredity of Intelligence and of Special Aptitudes 289
Intelligence and the Brain 292
Exercises 294
References 295
CHAPTER XIII
LEARNING AND HABIT FORMATION 296
Acquired Reactions Are Modified Native Reactions 297
Acquired Tendencies 299
Animal Learning 302
Summary of Animal Learning 310
Human Learning 311
Human Compared with Animal Learning 313
Learning by Observation 317
The Learning of Complex Practical Performances 321
Higher Units and Overlapping 323
Moderate Skill Acquired in the Ordinary Day's Work 326
Habit 328
Exercises 330
References 331
CHAPTER XIV
MEMORY 332
The Process of Memorizing 333
Economy in Memorizing 333
Unintentional Learning 346
Retention 348
Recall 364
Recognition 357
Memory Training 360
Exercises 364
References 365
CHAPTER XV
ASSOCIATION AND MENTAL IMAGERY 366
What Can Be Recalled 366
Memory Images 368
Limitations of Imagery 371
The Question of Non-Sensory Recall 373
Hallucinations 375
Free Association 376
Controlled Association 381
Examples of Controlled Association 384
Exercises 386
References 388
CHAPTER XVI
THE LAWS OF ASSOCIATION 389
The Law of Exercise 389
The Law of Effect 391
Limitations of the Law of Exercise 393
Association by Similarity 395
Association by Contiguity 396
The Law of Combination 398
The Law of Combination in Recall 413
The Laws of Learning in Terms of the Neurones 414
Exercises 418
References 418
CHAPTER XVII
PERCEPTION 418
Some Definitions 421
The Difference Between Perception and Sensation 423
Perception and Image 425
Perception and Motor Reaction 427
What Sort of Response, Then, Is Perception? 431
Practiced Perception 433
Corrected Perception 435
Sensory Data Serving as Signs of Various Sorts of Fact 437
The Perception of Space 439
Esthetic Perception 443
Social Perception 444
Errors of Perception 446
Illusions 450
Exercises 460
References 461
CHAPTER XVIII
REASONING 462
Animal and Human Exploration 463
Reasoning Culminates in Inference 465
Varieties of Reasoning 468
Deductive and Inductive Reasoning 474
Psychology and Logic 476
Exercises 480
References 480
CHAPTER XIX
IMAGINATION 481
Beginnings of Imagination in the Child 482
Preliminary Definition of Imagination 483
Play 485
The Play Motives 488
Empathy 491
Worry 497
Day Dreams 498
Dreams 499
Freud's Theory of Dreams 505
Autistic Thinking 508
Invention and Criticism 509
The Enjoyment of Imaginative Art 512
The Psychology of Inventive Production 517
Imagination Considered in General 519
Exercises 521
References 522
CHAPTER XX
WILL 523
Voluntary and Involuntary Action 524
Development of Voluntary Control 526
Ideomotor Action 527
Conflict and Decision 528
Obstruction and Effort 535
Thought and Action 539
Securing Action 541
The Influence of Suggestion 546
Exercises 551
References 561
CHAPTER XXI
PERSONALITY 552
Factors in Personality 553
The Self 555
Integration and Disintegration of the Personality 558
The Unconscious, or, the Subconscious Mind 561
Unconscious Wishes and Motives 565
Exercises 571
References 571
INDEX 573
{1}
PSYCHOLOGY
CHAPTER I
WHAT PSYCHOLOGY IS AND DOES
THE SUBJECT-MATTER OF THE SCIENCE, ITS PROBLEMS AND ITS METHODS
Modern psychology is an attempt to bring the methods of scientific investigation, which have proved immensely fruitful in other fields, to bear upon mental life and its problems. The human individual, the main object of study, is so complex an object, that for a long time it seemed doubtful whether there ever could be real science here; but a beginning was made in the nineteenth century, following the lead of biology and physiology, and the work of the investigator has been so successful that to-day there is quite a respectable body of knowledge to assemble under the title of scientific psychology.
Psychology, then, is a science. It is the science of—what shall we say? "The science of the soul"—that is what the name means by derivation and ancient usage. "The science of the mind" has a more modern sound. "The science of consciousness" is more modern still. "The science of behavior" is the most recent attempt at a concise formula.
None of these formulas is wholly satisfactory. Psychology does not like to call itself the science of the soul, for that has a theological tang and suggests problems that have so far not seemed accessible to scientific investigation. Psychology does not like very well to call itself the science {2} of the mind, as the mind seems to imply some thing or machine, and there is no such thing to be observed (unless it be the brain and body generally), and, anyway, psychology is distinctly a study of actions rather than of things. Psychology does not like to limit itself to the study of consciousness, but finds it necessary to study also unconscious actions. As to "behavior", it would be a very suitable term, if only it had not become so closely identified with the "behavioristic movement" in psychology, which urges that consciousness should be entirely left out of psychology, or at least disregarded. "Behavior psychology", as the term would be understood to-day, means a part of the subject and not the whole.
[Footnote: A series of waggish critics has evolved the following: "First psychology lost its soul, then it lost its mind, then it lost consciousness; it still has behavior, of a kind."]
The best way of getting a true picture of psychology, and of reaching an adequate definition of its subject-matter, would be to inspect the actual work of psychologists, so as to see what kind of knowledge they are seeking. Such a survey would reveal quite a variety of problems under process of investigation, some of them practical problems, others not directly practical.
Varieties of Psychology
Differential psychology.
One line of question that always interests the beginner in psychology is as to how people differ—how different people act under the same circumstances—and why; and if we watch the professional psychologist, we often find him working at just this problem. He tests a great number of individuals to see how they differ, and tries to discover on what factors their differences depend, how far on heredity, how far on environment. The "psychologist" in such a place as the children's court {3} is a specialist whose duty it is to test the delinquent children that are brought before the court, with the special object of measuring the intelligence of each individual child and of helping in other ways to understand the child's peculiar conduct and attitude.
The "psychological examiner" in the Army, during the Great War, had the same general object in view. It was desirable to measure the intelligence of each recruit as he entered the service, since military experience had shown that men of low intelligence made poor soldiers, while those of high intelligence made the best officers and non-commissioned officers, provided they also possessed good physique and certain less measureable mental qualifications, such as courage and leadership.
Applied psychology.
The Army psychologists, like the court psychologist, were engaged in applying scientific knowledge to the practical problems of life; and there are many other applications of psychology, to education, to medicine, to business and other occupations, as well as to the art of right living. Scientific knowledge enables you to predict and control. Having devised scientific tests for intelligence, you can predict of a six-year-old boy who tests low, that he will not get much good from the regular classes in school; and thus you are in a position to control the education of this boy for his own best interests. In the Army, it happened during the earlier part of the war that some companies or regiments made much slower progress in training than others; and a whole Division was delayed for months because of the backwardness of a single regiment. When the psychological tests were introduced, these slow-learning units were found to contain a disproportionate number of men of low intelligence. From that time on, it was possible by aid of the tests to equalize the intelligence of different units when first formed, and thus insure equal {4} progress in training. This was a good example of "control".
Most of us are attracted by the practical use of a science, and some have no patience with any study that does not seem immediately practical. But really any science, however much it is applied, must remain fundamentally a pure science; that is, it must seek most of all to know and understand. Practical scientific knowledge was usually first obtained without any inkling of how it might be used. The science of electricity is the most striking example of this. It began as an attempt to understand certain curious phenomena, which seemed to be nothing but curiosities; yet when the knowledge of these phenomena had progressed to a certain point, abundant use was found for it. Much the same is true of psychology, which began as a pure science and only recently has found ways of applying its discoveries to practical affairs. So the student beginning the science, though properly desirous of making practical use of what he learns, should let himself be governed for the present by the desire to know and understand, confident that the more scientific (which is to say, the more complete, systematic and reliable) his knowledge is, the more available it will be for practical application.
General psychology.
Our science is not concerned entirely with differences between people, but asks also in what ways people are alike, and this is indeed its central problem. How do "we" observe, learn, remember, imagine, think? What sensations and feelings do we have, what emotions, what instincts, what natural and acquired impulses to action? How are our natural powers and impulses developed and organized as we grow up? Psychology is concerned with the child as well as the adult, and it is even concerned with the animal. It is concerned with the abnormal as well as the normal human being. So you will find books and {5} courses on animal psychology, child psychology, abnormal psychology. Now general psychology—or just plain "psychology"—has to do with the main laws and principles that hold in all these special fields.
Psychology as Related to Other Sciences
A good definition of our science would distinguish it from other sciences, especially from those neighboring sciences with which it is in closest contact.
Psychology and sociology.
There is no difficulty in framing a good logical distinction here. Sociology studies the activities of a group of people taken as a whole, while psychology studies the activities of the individuals. Both might be interested in the same social act, such as an election, but sociology would consider this event as a unit, whereas psychology would break it up into the acts of the several voters. The distinction is clear enough theoretically, but breaks down often in practice, as sociology would like to know the motives that swayed individual voters, while psychology on its side is interested to know what decision was reached by the majority. All the social sciences, including economics and politics, have a psychological side, since they evidently are concerned to know the causes that govern human conduct. Social psychology studies the individual in his social relations.
Psychology and biology.
Biology, being the science of living creatures, includes psychology, which studies these creatures on the mental side. The science of life includes the science of mental life. We may call psychology a part of biology, or we may call it one of the biological sciences. It has very close contact with several other branches of biology. Animal psychology overlaps that part of zoology which studies the behavior of animals. Genetic psychology, as it is sometimes called, i.e., the study of mental heredity. {6} and development, dovetails with the general biological science of genetics, so that we find biologists gathering data on the heredity of feeble-mindedness or of musical ability, while psychologists discuss the general theory of heredity.
Psychology and physiology.
That one of all the sciences that has the closest contacts with psychology is human and animal physiology. Broadly defined, physiology is that part of biology that studies functions or activities; and, so defined, it includes psychology as part of itself. In practice, psychology devotes itself to desire, thought, memory, and such "mental functions", while physiology concentrates its effort upon "bodily functions" like digestion and circulation. But this is only a rough distinction, which breaks down at many points.
Where shall we class sensation? Is it "mental" or "bodily"? Both sciences study it. Physiology is perhaps more apt to go into the detailed study of the action of the sense organs, and psychology to concern itself with the classification of sensations and the use made of them for recognizing objects or for esthetic purposes. But the line between the two sciences is far from sharp at this point.
Speech, also, lies in both provinces. Physiology has studied the action of the vocal organs and the location of the brain centers concerned in speech, while psychology has studied the child's process of learning to speak and the relation of speech to thought, and is more apt to be interested in stuttering, slips of the tongue, and other speech disturbances which are said to be "mental rather than physical".
It would be hard to mention any activity that is mental without being physical at the same time. Even thinking, which seems as purely mental as any, requires brain action; and the brain is just as truly a bodily organ as the heart or stomach. Its activity is bodily activity and lies properly within the field of physiology.
{7}
But it would be equally difficult to mention any function that is exclusively bodily, and not mental at the same time, in some degree. Take digestion for example: the pleasant anticipation of food will start the digestive juices flowing, before any food is physically in the stomach; while in anger or fear digestion comes to a sudden halt. Therefore we find physiologists interested in these emotions, and psychologists interested in digestion.
We do not find any clean separation between our science and physiology; but we find, on the whole, that psychology examines what are called "mental" activities, and that it studies them as the performances of the whole individual rather than as executed by the several organs.
The Science of Consciousness
Typically, the activities that psychology studies are conscious performances, while many of those falling to physiology are unconscious. Thus digestion is mostly unconscious, the heart beat is unconscious except when disturbed, the action of the liver is entirely unconscious. Why not say, then, that psychology is the study of conscious activities?
There might be some objection to this definition from the side of physiology, which studies certain conscious activities itself—speech, for example, and especially sensation.
There would be objection also from the side of psychology, which does not wish to limit itself to conscious action. Take the case of any act that can at first be done only with close attention, but that becomes easy and automatic after practice; at first it is conscious, later unconscious, but psychology would certainly need to follow it from the initial to the final stage, in order to make a complete study of the practice effect. And then there is the "unconscious", or the "subconscious mind"—a matter on which psychologists {8} do not wholly agree among themselves; but all would agree that the problem of the unconscious was appropriate to psychology.
For all the objections, it remains true that the typical mental process, the typical matter for psychological study, is conscious. "Unconscious mental processes" are distinguished from the unconscious activity of such organs as the liver by being somehow like the conscious mental processes.
It would be correct, then, to limit psychology to the study of conscious activities and of activities akin to these.
The Science of Behavior
No one has objected so strenuously to defining psychology as the science of consciousness, and limiting it to consciousness, as the group of animal psychologists. By energetic work, they had proved that the animal was a very good subject for psychological study, and had discovered much that was important regarding instinct and learning in animals. But from the nature of the case, they could not observe the consciousness of animals; they could only observe their behavior, that is to say, the motor (and in some cases glandular) activities of the animals under known conditions. When then the animal psychologists were warned by the mighty ones in the science that they must interpret their results in terms of consciousness or not call themselves psychologists any longer, they rebelled; and some of the best fighters among them took the offensive, by insisting that human psychology, no less than animal, was properly a study of behavior, and that it had been a great mistake ever to define it as the science of consciousness.
It is a natural assumption that animals are conscious, but after all you cannot directly observe their consciousness, and you cannot logically confute those philosophers {9} who have contended that the animal was an unconscious automaton. Still less can you be sure in detail what is the animal's sensation or state of mind at any time; to get at that, you would need a trustworthy report from the animal himself. Each individual must observe his own consciousness; no one can do it from outside. The objection of the behaviorist to "consciousness psychology" arises partly from distrust of this method of inner observation, even on the part of a human observer.
Indeed, we can hardly define psychology without considering its methods of observation, since evidently the method of observation limits the facts observed and so determines the character of the science. Psychology has two methods of observation.
When a person performs any act, there are, or may be, two sorts of facts to be observed, the "objective" and the "subjective". The objective facts consist of movements of the person's body or of any part of it, secretions of his glands (as flow of saliva or sweat), and external results produced by these bodily actions—results such as objects moved, path and distance traversed, hits on a target, marks made on paper, columns of figures added, vocal or other sounds produced, etc., etc. Such objective facts can be observed by another person.
The subjective facts can be observed only by the person performing the act. While another person can observe, better indeed than he can himself, the motion of his legs in walking, he alone can observe the sensations in the joints and muscles produced by the leg movement. No one else can observe his pleased or displeased state of mind, nor whether he is thinking of his walking or of something quite different. To be sure, his facial expression, which is an objective fact, may give some clue to his thoughts and feelings, but "there's no art to read the mind's construction {10} in the face", or at least no sure art. One may feign sleep or absorption while really attending to what is going on around. A child may wear an angelic expression while meditating mischief. To get the subjective facts, we shall have to enlist the person himself as our observer.
Introspection
This is observation by an individual of his own conscious action. It is also called subjective observation. Notice that it is a form of observation, and not speculation or reasoning from probabilities or from past experience. It is a direct observation of fact.
One very simple instance of introspection is afforded by the study of after-images. Look for an instant at the glowing electric bulb, and then turn your eyes upon a dark background, and observe whether the glowing filament appears there; this would be the "positive after-image". This simple type of introspection is used by physiology in its study of the senses, as well as by psychology; and it gives such precise and regular results that only the most confirmed behaviorists refuse to admit it as a good method of observation.
But psychology would like to make introspective observations on the more complex mental processes as well; and it must be admitted that here introspection becomes difficult. You cannot hope to make minute observations on any process that lasts over a very few seconds, for you must let the process run its natural course unimpeded by your efforts at observing it, and then turn your "mental eye" instantly back to observe it retrospectively before it disappears. As a matter of fact, a sensation or feeling or idea hangs on in consciousness for a few seconds, and can be observed in this retrospective way. There is no theoretical objection to this style of introspection, but it is practically difficult and {11} tricky. Try it on a column of figures: first add the column as usual, then immediately turn back and review exactly what went through your mind in the process of adding—-what numbers you spoke internally, etc. Try again by introspecting the process of filling in the blanks in the sentence:
"Botany could not make use of introspection because _ have probably no __ processes."
At first, you may find it difficult to observe yourself in this way; for the natural tendency, when you are aiming at a certain result, is to reach the goal and then shift to something else, rather than to turn back and review the steps by which you reached the goal. But with practice, you acquire some skill in introspection.
One difficulty with introspection of the more complex mental processes is that individuals vary more here than in the simpler processes, so that different observers, observing each his own processes, will not report the same facts, and one observer cannot serve as a check upon another so easily as in the simpler introspection of after-images and other sensations, or as in the observations made in other sciences. Even well trained introspectionists are quite at variance when they attempt a minute description of the thought processes, and it is probable that this is asking too much of introspection. We mustn't expect it to give microscopic details. Rough observations, however, it gives with considerable certainty. Who can doubt, for example, that a well-practised act goes on with very little consciousness, or that inner, silent speech often accompanies thinking? And yet we have only introspection to vouch for these facts.
Objective Observation
But to say, as used to be said, that psychology is purely an introspective science, making use of no other sort of observation, is absurd in the face of the facts.
{12}
We have animal psychology, where the observation is exclusively objective. In objective observation, the observer watches something else, and not himself. In animal psychology, the psychologist, as observer, watches the animal.
The same is true of child psychology, at least for the first years of childhood. You could not depend on the introspections of a baby, but you can learn much by watching his behavior. Abnormal persons, also, are not often reliable introspectionists, and the study of abnormal psychology is mostly carried on by objective methods.
Now how is it with the normal adult human being, the standard subject for psychology? Does he make all the observations on himself or may he be objectively observed by the psychologist? The latter, certainly. In fact, nearly all tests, such as those used in studying differential psychology, are objective. That is to say that the person tested is given a task to perform, and his performance is observed in one way or another by the examiner. The examiner may observe the time occupied by the subject to complete the task, or the quantity accomplished in a fixed time; or he may measure the correctness and excellence of the work done, or the difficulty of the task assigned. One test uses one of these measures, and another uses another; but they are all objective measures, not depending at all on the introspection of the subject.
What is true of tests in differential psychology is true of the majority of experiments in general psychology: the performer is one person, the observer another, and the observation is objective in character. Suppose, for example, you are investigating a memory problem; your method may be to set your subject a lesson to memorize under certain defined conditions, and see how quickly and well he learns it; then you give him another, equally difficult lesson to be learned under altered conditions, and observe whether he {13} does better or worse than before. Thus you discover which set of conditions is more favorable for memorizing, and thence can infer something of the way in which memorizing is accomplished. In the whole experiment you need not have called on your subject for any introspections; and this is a type of many experiments in which the subject accomplishes a certain task under known conditions, and his success is objectively observed and measured.
There is another type of objective psychological observation, directed not towards the success with which a task is accomplished, but towards the changes in breathing, heart beat, stomach movements, brain circulation, or involuntary movements of the hands, eyes, etc., which occur during the course of various mental processes, as in reading, in emotion, in dreaming or waking from sleep.
Now it is not true as a matter of history that either of these types of objective observation was introduced into psychology by those who call themselves behaviorists. Not at all; experiments of both sorts have been common in psychology since it began to be an experimental science. The first type, the success-measuring experiment, has been much more used than introspection all along. What the behaviorists have accomplished is the definitive overthrow of the doctrine, once strongly insisted on by the "consciousness psychologists", that introspection is the only real method of observation in psychology; and this is no mean achievement. But we should be going too far if we followed the behaviorists to the extent of seeking to exclude introspection altogether, and on principle. There is no sense in such negative principles. Let us accumulate psychological facts by any method that will give the facts.
{14}
General Laws of Psychological Investigation.
Either introspective or objective observation can be employed in the experimental attack on a problem, which consists, as just illustrated in the case of memory, in controlling the conditions under which a mental performance occurs, varying the conditions systematically, and noting the resulting change in the subject's mental process or its outcome. Psychologists are inclined to regard this as the best line of attack, whenever the mental activity to be studied can be effectively subjected to control. Unfortunately, emotion and reasoning are not easily brought under control, and for this reason psychology has made slower progress in understanding them than it has made in the fields of sensation and memory, where good experimental procedure has been developed.
Another general line of attack worthy to be mentioned alongside of the experimental is the comparative method. You compare the actions of individuals, classes or species, noting likenesses and differences. You see what behavior is typical and what exceptional. You establish norms and averages, and notice how closely people cluster about the norm and how far individuals differ from it. You introduce tests of various sorts, by which to get a more precise measure of the individual's performance. Further, by the use of what may be called double comparison, or "correlation", you work out the relationships of various mental (and physical) traits. For example, when many different species of animals are compared in intelligence and also in brain weight, the two are found to correspond fairly well, the more intelligent species having on the whole the heavier brains; from which we fairly conclude that the size of the brain has something to do with intelligence. But when we correlate brain weight and intelligence in human individuals. {15} we find so many exceptions to the rule (stupid men with large brains and gifted men with brains of only moderate size) that we are forced to recognize the importance of other factors, such as the perfection of the microscopic structure of the brain.
Tests and correlations have become so prominent in recent psychological investigation that this form of the comparative method ranks on a par with the strict experimental method. A test is an experiment, in a way, and at least is often based upon an experiment; but the difference between the two lines of attack is that an experiment typically takes a few subjects into the laboratory and observes how their mental performances change with planfully changed conditions; whereas a test goes out and examines a large number of persons under one fixed set of conditions. An experiment belongs under what we called "general psychology", and a test under "differential psychology", since the first outcome of a test is to show how the individual differs from others in a certain respect. The results may, however, be utilized in various ways, either for such practical purposes as guiding the individual's choice of an occupation, or for primarily scientific purposes, such as examining whether intelligence goes with brain size, whether twins resemble each other as much mentally as they do physically, whether intellectual ability and moral goodness tend on the whole to go together, or not.
The genetic method is another of the general lines of attack on psychological problems. The object here is to trace the mental development of the individual, or of the race. It may be to trace the development either of mentality in general, or of some particular mental performance. It may be to trace the child's progress in learning to speak, or to follow the development of language in the human species, from the most primitive tongues up to those of the great {16} civilized peoples of to-day. It may be to trace the improvement of a performance with continued practice.
The value of the genetic method is easily seen. Usually the beginnings of a function or performance are comparatively simple and easy to observe and analyze. Also, the process of mental growth is an important matter to study on its own account.
The pathological method is akin to the genetic, but traces the decay or demoralization of mental life instead of its growth. It traces the gradual decline of mental power with advancing age, the losses due to brain disease, and the maladaptations that appear in insanity and other disturbances. Here psychology makes close contact with psychiatry which is the branch of medicine concerned with the insane, etc., and which in fact has contributed most of the psychological information derived from the pathological method.
The object of the pathological method is, on the one side, to understand abnormal forms of mental life, with the practical object of preventing or curing them, and on the other side, to understand normal mental life the better. Just as the development of a performance throws light on the perfected act, so the decay or disturbance of a function often reveals its inner workings; for we all know that it is when a machine gets out of order that one begins to see how it ought to work. Failure sheds light on the conditions of success, maladaptation throws into relief the mental work that has to be done by the normal individual in order to secure and maintain his good adaptation. According to the psychiatrists, mental disturbance is primarily an affair of emotion and desire rather than of intellect; and consequently they believe that the pathological method is of special importance in the study of the emotional life.
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Summary and Attempt at a Definition
Having now made a rapid preliminary survey of the field of psychology, and of the aims and methods of the workers in this field, we ought to be in a position to give some sort of a definition.
We conclude, then: psychology is a part of the scientific study of life, being the science of mental life. Life consisting in process or action, psychology is the scientific study of mental processes or activities. A mental activity is typically, though not universally, conscious; and we can roughly designate as mental those activities of a living creature that are either conscious themselves or closely akin to those that are conscious. Further, any mental activity can also be regarded as a physiological activity, in which case it is analyzed into the action of bodily organs, whereas as "mental" it simply comes from the organism or individual as a whole. Psychology, in a word, is the science of the conscious and near-conscious activities of living individuals.
Psychology is not interested either in dead bodies or in disembodied spirits, but in living and acting individuals.
One word more, on the psychological point of view. In everyday life we study our acquaintances and their actions from a personal standpoint. That is, we evaluate their behavior according as it affects ourselves, or, perhaps, according as it squares or not with our standards of right and wrong. We always find something to praise or blame. Now, the psychologist has no concern with praise and blame, but is a seeker after the facts. He would know and understand human actions, rather than pass judgment on them. When, for example, he is introduced into the school or children's court, for the purpose of examining children that are "problems", his attitude differs considerably from that of the {18} teacher or officer of the law; for while they almost inevitably pass judgment on the child in the way of praise or blame, the psychologist simply tries to understand the child. The young delinquent brought into the laboratory of the court psychologist quickly senses the unwonted atmosphere, where he is neither scolded nor exhorted, but asked to lend his cooeperation in an effort to discover the cause why his conduct is as it is. Now, this psychological attitude is not necessarily "better" than the other, but it is distinctly valuable in its place, as seen from the fact that the young delinquent often does cooeperate. He feels that if the psychologist can find out what is the trouble with him, this may help. Nothing, indeed, is more probable; it is when we have the facts and trace out cause and effect that we are in a fair way to do good. Nothing is more humane than psychology, in the long run, even though the psychologist may seem unfeeling in the course of his investigation.
To the psychologist, conduct is a matter of cause and effect, of natural law. His business is to know the laws of that part of nature which we call human nature, and to use these laws, as fast as discovered, for solving the problems presented by the human individual or group. For him, even the most capricious conduct has its causes, even the most inexplicable has its explanation—if only the cause can be unearthed, which he does not pretend he can always actually accomplish, since causes in the mental realm are often very complex. No one can be a psychologist all of the time; no one can or should always maintain this matter-of-fact attitude towards self and neighbor. But some experience with the psychological attitude is of practical value to any one, in giving clearer insight, more toleration, better control, and even saner standards of living.
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EXERCISES
1. Outline the chapter. A sample outline of the briefer sort is here given:
A. Subject-matter of psychology: mental activities.
(1) A sub-class under vital activities.
(2) Activities of individuals, as distinguished from
(a) Activities of social groups (sociology).
(b) Activities of single organs (physiology).
(3) Either conscious, or closely related to conscious activities.
(4) May be activities of human or animal, adult or child, normal or abnormal individuals.
B. Problems of psychology:
(1) How individuals differ in their mental activities.
(2) How individuals are alike in their mental activities.
(3) Practical applications of either (1) or (2).
C. Methods of psychology:
(1) Methods of observing mental activities.
(a) Introspective, the observing by an individual of his own actions.
(b) Objective, the observation of the behavior of other individuals.
(2) General lines of attack upon psychological problems.
(a) Experimental: vary the conditions and see how the mental activity changes.
(b) Comparative: test different individuals or classes and see how mental activity differs, etc.
(c) Genetic: trace mental development.
(d) Pathological: examine mental decay or disturbance.
2. Formulate a psychological question regarding each of the following: hours of work, genius, crime, baseball.
3. Distinguish introspection from theorizing.
4. What different sorts of objective fact can be observed in psychology?
5. What is the difference between the physiology of hearing and the psychology of hearing?
6. State two reasons why it would be undesirable to limit psychology to the introspective study of consciousness.
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7. What is the difference between an experiment and a test, (a) in purpose, (b) in method?
8. Compare the time it takes you to add twenty one-place numbers, arranged in a vertical column, and arranged in a horizontal line, (a) Is this introspective or objective observation? Why so? (b) Is it a test or an experiment? Why?
9. Write a psychological sketch of some one you know well, taking care to avoid praise and blame, and to stick to the psychological point of view.
REFERENCES
Some of the good books on the different branches of psychology are the following:
On animal psychology:
Margaret F. Washburn, The Animal Mind, 2nd edition, 1917.
John B. Watson, Behavior, 1914.
On child psychology:
Norsworthy and Whitley, The Psychology of Childhood, 1918.
On abnormal psychology:
A. J. Rosanoff, Manual of Psychiatry, 5th edition, 1920.
On applied psychology:
Hollingworth and Poffenberger, Applied Psychology, 1917.
On individual psychology, parts of:
E. L. Thorndike, Educational Psychology, Briefer Course, 1914,
Daniel Starch, Educational Psychology, 1919.
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CHAPTER II
REACTIONS
REFLEXES AND OTHER ELEMENTARY FORMS OF REACTION, AND HOW THE NERVES OPERATE IN CARRYING THEM OUT
Having the field of psychology open before us, the next question is, where to commence operations. Shall we begin with memory, imagination and reasoning, or with will, character and personality, or with motor activity and skill, or with feelings and emotions, or with sensation and perceptions? Probably the higher forms of mental activity seem most attractive, but we may best leave complicated matters till later, and agree to start with the simplest sorts of mental performance. Thus we may hope to learn at the outset certain elementary facts which will later prove of much assistance in unraveling the more complex processes.
Among the simplest processes are sensations and reflexes, and we might begin with either. The introspective psychologists usually start with sensations, because their great object is to describe consciousness, and they think of sensations as the chief elements of which consciousness is composed. The behaviorists would prefer to start with reflexes, because they conceive of behavior as composed of these simple motor reactions.
Without caring to attach ourselves exclusively to either introspectionism or behaviorism, we may take our cue just here from the behaviorists, because we shall find the facts of motor reaction more widely useful in our further studies than the facts of sensation, and because the facts of {22} sensation fit better into the general scheme of reactions than the facts of reaction fit into any general scheme based on sensation.
A reaction is a response to a stimulus. The response, in the simplest cases, is a muscular movement, and is called a "motor response". The stimulus is any force or agent that, acting upon the individual, arouses a response.
If I start at a sudden noise, the noise is the stimulus, and the forcible contraction of my muscles is the response. If my old friend's picture brings tears to my eyes, the picture (or the light reflected from it) is the stimulus, and the flow of tears is the response, here a "glandular" instead of a motor response.
The Reaction Time Experiment
One of the earliest experiments to be introduced into psychology was that on reaction time, conducted as follows: The experimenter tells his "subject" (the person whose reaction is to be observed) to be ready to make a certain movement as promptly as possible on receiving a certain stimulus. The response prescribed is usually a slight movement of the forefinger, and the stimulus may be a sound, a flash of light, a touch on the skin, etc. The subject knows in advance exactly what stimulus is to be given and what response he has to make, and is given a "Ready!" signal a few seconds before the stimulus. With so simple a performance, the reaction time is very short, and delicate apparatus must be employed to measure it. The "chronoscope" or clock used to measure the reaction time reads to the hundredth or thousandth of a second, and the time is found to be about .15 sec. in responding to sound or touch, about .18 sec. in responding to light.
Even the simple reaction time varies, however, from one {23} individual to another, and from one trial to another. Some persons can never bring their record much below the figures stated, while a few can get the time down to .10 sec, which is about the limit of human ability. Every one is bound to vary from trial to trial, at first widely, after practice between narrow limits, but always by a few hundredths of a second at the least. It is curious to find the elementary fact of variability of reaction present in such a simple performance.
What we have been describing is known as the "simple reaction", in distinction from other experiments that demand more of the subject. In the "choice reaction", there are two stimuli and the subject may be required to react to the one with the right hand and to the other with the left; for example, if a red light appears he must respond with the right hand, but if a green light appears, with the left. Here he cannot allow himself to become keyed up to as high a pitch as in the simple reaction, for if he does he will make many false reactions. Therefore, the choice reaction time is longer than the simple reaction time—about a tenth of a second longer.
The "associative reaction" time is longer still. Here the subject must name any color that is shown, or read any letter that is shown, or respond to the sight of any number by calling out the next larger number, or respond to any suitable word by naming its opposite. He cannot be so well prepared as for the simple, or choice reaction, since he doesn't know exactly what the stimulus is going to be; also, the brain process is more complex here; so that the reaction time is longer, about a tenth of a second longer, at the best, than the choice reaction. It may run up to two or three seconds, even in fairly simple cases, while if any serious thinking or choosing has to be done, it runs into many seconds and even into minutes. Here the brain process is very {24} complex and involves a series of steps before the required motor response can be made.
These laboratory experiments can be paralleled by many everyday performances. The runner starting at the pistol shot, after the preparatory "Ready! Set!", and the motorman applying the brakes at the expected sound of the bell, are making "simple" reactions. The boxer, dodging to the right or the left according to the blow aimed at him by his adversary, is making choice reactions, and this type is very common in all kinds of steering, handling tools and managing machinery. Reading words, adding numbers, and a large share of simple mental performances, are essentially associative reactions. In most cases from ordinary life, the preparation is less complete than in the laboratory experiments, and the reaction time is accordingly longer.
Reflex Action
The simple reaction has some points of resemblance with the "reflex", which, also, is a prompt motor response to a sensory stimulus. A familiar example is the reflex wink of the eyes in response to anything touching the eyeball, or in response to an object suddenly approaching the eye. This "lid reflex" is quicker than the quickest simple reaction, taking about .05 second. The knee jerk or "patellar reflex", aroused by a blow on the patellar tendon just below the knee when the knee is bent and the lower leg hanging freely, is quicker still, taking about .03 second. The reason for this extreme quickness of the reflex will appear as we proceed. However, not every reflex is as quick as those mentioned, and some are slower than the quickest of the simple reactions.
A few other examples of reflexes may be given. The "pupillary reflex" is the narrowing of the pupil of the eye {25} in response to a bright light suddenly shining into the eye. The "flexion reflex" is the pulling up of the leg in response to a pinch, prick or burn on the foot. Coughing and sneezing are like this in being protective reflexes, and the scratching of the dog belongs here also.
There are many internal reflexes: movements of the stomach and intestines, swallowing and hiccoughing, widening and narrowing of the arteries resulting in flushing and paling of the skin. These are muscular responses; and there are also glandular reflexes, such as the discharge of saliva from the salivary glands into the mouth, in response to a tasting substance, the flow of the gastric juice when food reaches the stomach, the flow of tears when a cinder gets into the eye. There are also inhibitory reflexes, such as the momentary stoppage of breathing in response to a dash of cold water. All in all, a large number of reflexes are to be found.
Most reflexes can be seen to be useful to the organism. A large proportion of them are protective in one way or another, while others might be called regulative, in that they adjust the organism to the conditions affecting it.
Now comparing the reflex with the simple reaction, we see first that the reflex is more deep-seated in the organism, and more essential to its welfare. The reflex is typically quicker than the simple reaction. The reflex machinery does not need a "Ready" signal, nor any preparation, but is always ready for business. (The subject in a simple reaction experiment would not make the particular finger movement that he makes unless he had made ready for that movement.) The attachment of a certain response to a certain stimulus, rather arbitrary and temporary in the simple reaction, is inherent and permanent in the reflex. Reflex action is involuntary and often entirely unconscious.
Reflexes, we said, are permanent. That is because they {26} are native or inherent in the organism. You can observe them in the new-born child. The reflex connection between stimulus and response is something the child brings with him into the world, as distinguished from what he has to acquire through training and experience. He does acquire, as he grows up, a tremendous number of habitual responds that become automatic and almost unconscious, and these "secondary automatic" reactions resemble reflexes pretty closely. Grasping for your hat when you feel the wind taking it from your head is an example. These acquired reactions never reach the extreme speed of the quickest reflexes, but at best may have about the speed of the simple reaction. Though often useful enough, they are not so fundamentally necessary as the reflexes. The reflex connection of stimulus and response is something essential, native, closely knit, and always ready for action.
The Nerves in Reflex Action
Seeing that the response, in reflex action, is usually made by a muscle or gland lying at some distance from the sense organ that receives the stimulus—as, in the case of the flexion reflex, the stimulus is applied to the skin of the hand (or foot), while the response is made by muscles of the limb generally—we have to ask what sort of connection exists between the stimulated organ and the responding organ, and we turn to physiology and anatomy for our answer. The answer is that the nerves provide the connection. Strands of nerve extend from the sense organ to the muscle.
But the surprising fact is that the nerves do not run directly from the one to the other. There is no instance in the human body of a direct connection between any sense organ and any muscle or gland. The nerve path from sense organ to muscle always leads through a nerve center. One {27} nerve, called the sensory nerve, runs from the sense organ to the nerve center, and another, the motor nerve, runs from the center to the muscle; and the only connection between the sense organ and the muscle is this roundabout path through the nerve center. The path consists of three parts, sensory nerve, center, and motor nerve, but, taken as a whole, it is called the reflex arc, both the words, "reflex" and "arc", being suggested by the indirectness of the connection.
The nervous system resembles a city telephone system. What passes along the nerve is akin to the electricity that {28} passes along the telephone wire; it is called the "nerve current", and is electrical and chemical in nature.
All nerve connections, like the great majority of telephone connections, are effected through the centers, called "centrals" in {29} the case of the telephone. Telephone A is connected directly with the central, telephone B likewise, and A and B are indirectly connected, through the central switchboard. That is the way it is in the nervous system, with "nerve center" substituted for "central", and "sense organ" and "muscle or gland" for "telephones A and B."
The advantage of the centralized system is that it is a system, affording connections between any part and any other, and unifying the whole complex organism.
The nerve centers are located in the brain and spinal cord. The brain lies in the skull and the cord extends from the brain down through a tube in the middle of the {30} backbone. Of the brain many parts can be named, but for the present it is enough to divide it into the "brain stem", a continuation of the spinal cord up along the base of the skull cavity, and the two great outgrowths of the brain stem, called "cerebrum" and "cerebellum". The spinal cord and brain stem contain the lower or reflex centers, while the cerebellum, and especially the cerebrum, contain the "higher centers". The lower centers are directly connected by nerves with the sense organs, glands and muscles, while the higher centers have direct connections with the lower and only through them with the sense organs, glands and muscles. In other words, the sensory nerves run into the cord or brain stem, and the motor nerves run out of these same, while interconnecting nerve strands extend between the lower centers in the cord and brain stem and the higher centers in the cerebrum and cerebellum.
The spinal cord contains the reflex centers for the limbs and part of the trunk, and is connected by sensory and motor nerves with the limbs and trunk. The brain stem contains the reflex centers for the head and also for part of the interior of the trunk, including the heart and lungs, and is connected with them by sensory and motor nerves. The nerve center that takes part in the flexion reflex of the foot is situated in the lower part of the cord, that for the similar reflex of the hand lies in the upper part of the cord, that for breathing lies in the lower or rear part of the brain stem, and that for winking lies further forward in the brain stem.
Big movements, such as the combined action of all four legs of an animal in walking, require cord and brain stem to work together, and throw into relief what is really true even of simpler reflexes, namely that a reflex is a coordinated movement, in the sense that different muscles cooperate in its execution.
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Internal Construction of the Nerves and Nerve Centers
We shall understand nerve action better if we know something of the way in which the nervous system is built. A nerve is not to be thought of as a unit, nor are the brain and cord to be thought of as mere masses of some peculiar substance.
A nerve is a bundle of many slender insulated threads, just as a telephone cable, running along the street, {32} is a bundle of many separate wires which are the real units of telephonic communication. A nerve center, like the switchboard in a telephone central, consists of many parts and connections.
The whole nervous system is essentially composed of neurones. A neurone is a nerve cell with its branches. Most nerve cells have two kinds of branches, called the axon and the dendrites.
The nerve cell is a microscopic speck of living matter. Its dendrites are short tree-like branches, while its axon is often several inches or even feet in length. The axon is the "slender thread", just spoken of as analogous to the single telephone wire. A nerve is composed of axons. [Footnote: The axon is always protected or insulated by a sheath, and axon and sheath, taken together, are often called a "nerve fiber".] The "white matter" of the brain and cord is composed of axons. Axons afford the means of communication between the nerve centers and the muscles and sense organs, and between one nerve center and another.
The axons which make up the motor nerves are branches of nerve cells situated in the cord and brain stem; they extend from the reflex center for any muscle out to and into that muscle and make very close connection with the muscle substance. A nerve current, starting from the nerve cells in the reflex center, runs rapidly along the axons to the muscle and arouses it to activity.
The axons which make up the optic nerve, or nerve of sight, are branches of nerve cells in the eye, and extend into the brain stem. Light striking the eye starts nerve currents, which run along these axons into the brain stem. Similarly, the axons of the nerve of smell are branches of cells in the nose.
The remainder of the sensory axons are branches of nerve cells that lie in little bunches close alongside the cord or {33} brain stem. These cells have no dendrites, but their axon, dividing, reaches in one direction out to a sense organ and in the other direction into the cord or brain stem, and thus connects the sense organ with its "lower center".
Where an axon terminates, it broadens out into a thin plate, or breaks up into a tuft of very fine branches ( the "end-brush"), and by this means makes close contact with the muscle, the sense organ, or the neurone with which it connects.
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The Synapse
Now let us consider the mode of connection between one neurone and another in a nerve center. The axon of one neurone, through its end-brush, is in close contact with the dendrites of another neurone. There is contact, but no actual growing-together; the two neurones remain distinct, and this contact or junction of two neurones is called a "synapse". The synapse, then, is not a thing, but simply a junction between two neurones.
The junction is good enough so that one of the two neurones, if itself active, can arouse the other to activity. The end-brush, when a nerve current reaches it from its own nerve cell, arouses the dendrites of the other neurone, and thus starts a nerve current running along those dendrites to their nerve cell and thence out along its axon.
Now here is a curious and significant fact: the dendrites are receiving organs, not transmitting; they pick up messages from the end-brushes across the synapse, but send out no messages to those end-brushes. Communication across a synapse is always in one direction, from end-brush to dendrites.
This, then, is the way in which a reflex is carried out, the pupillary reflex, for example. Light entering the eye starts a nerve current in the axons of the optic nerve; these axons terminate in the brain stem, where their end-brushes arouse the dendrites of motor nerve cells, and the axons of these {35} cells, extending out to the muscle of the pupil, cause it to contract, and narrow the pupil.
Or again, this is the way in which one nerve center arouses another to activity. The axons of the cells in the first center (or some of them) extend out of this center and through the white matter to the second center, where they terminate, their end-brushes forming synapses with the cells of the second center. Let the first center be thrown into activity, and immediately, through this connection, it arouses the second.
[Illustration: Fig. 7.—Different forms of synapse found in the cerebellum, "a" is one of the large motor cells of the cerebellum (a "Purkinje cell"), with its dendrites above and its axon below; and "b," "c" and "d" show three forms of synapse made by other neurones with this Purkinje cell. In "b," the arrow indicates a "climbing axon," winding about the main limbs of the Purkinje cell. In "c," the arrow points to a "basket"—an end-brush enveloping the cell body; while "d" shows what might be called a "telegraph-wire synapse." Imagine "d" superimposed upon "a": the axon of "d" rises among the fine dendrites of "a," and then runs horizontally through them; and there are many, many such axons strung among the dendrites. Thus the Purkinje cell is stimulated at three points: cell body, trunks of the dendrites, and twigs of the dendrites.]
The "gray matter" comprises the nerve centers, lower and higher. It is made up of nerve cells and their dendrites, of the beginnings of axons issuing from these cells and of the terminations of incoming axons. The white matter, as was said before, consists of axons. An axon issues from the {36} gray matter at one point, traverses the white matter for a longer or shorter distance, and finally turns into the gray matter at another point, and thus nerve connection is maintained between these two points.
There are lots of nerve cells, billions of them. That ought to be plenty, and yet—well, perhaps sometimes they are not well developed, or their synapses are not close enough to make good connections.
Examined under the microscope, the nerve cell is seen to contain, besides the "nucleus" which is present in every living cell and is essential for maintaining its vitality and special characteristics, certain peculiar granules which appear to be stores of fuel to be consumed in the activity of the cell, and numerous very fine fibrils coursing through the cell and out into the axon and dendrites.
The reflex arc can now be described more precisely than before. Beginning in a sense organ, it extends along a sensory axon (really along a team of axons acting side by side) to its end-brush in a lower center, where it crosses a synapse and enters the dendrites of a motor neurone and so {37} reaches the cell body and axon of this neurone, which last extends out to the muscle (or gland). The simplest reflex arc consists then of a sensory neurone and a motor neurone, meeting at a synapse in a lower or reflex center. This would be a two-neurone arc.
Very often, and possibly always, the reflex arc really consists of three neurones, a "central" neurone intervening between the sensory and motor neurones and being connected through synapses with each. The central neurone plays an important role in cooerdination.
COOeRDINATION
The internal structure of nerve centers helps us see how cooerdinated movement is produced. The question is, how {38} several muscles are made to work together harmoniously, and also how it is possible that a pin prick, directly affecting just a few sensory axons, causes a big movement of many muscles. Well, we find the sensory axon, as it enters the cord, sending off a number of side branches, each of which terminates in an end-brush in synaptic connection with the dendrites of a motor nerve cell.
Thus the nerve current from a single sensory neurone is distributed to quite a number of motor neurones. Where there are central neurones in the arc, their branching axons aid in distributing the excitation; and so we get a big movement in response to a minute, though intense stimulus.
But the response is not simply big; it is definite, coordinated, representing team work on the part of the muscles as distinguished from indiscriminate mass action. That means selective distribution of the nerve current. The axons of the sensory and central neurones do not connect with any and every motor neurone indiscriminately, but link up with selected groups of motor neurones, and thus harness together teams that will work in definite ways, producing {39} flexion of a limb in the case of one such team, and extension in the case of another. Every reflex has its own team of motor neurones, harnessed together by its outfit of sensory and central neurones. The same motor neurone may however be harnessed into two or more such teams, as is seen from the fact that the same muscle may participate in different reflex movements; and for a similar reason we believe that the same sensory neurone may be utilized in more than one reflex arc.
The most distinctive part of any reflex arc is likely to be its central neurones, which are believed to play the chief part in cooerdination, and in determining the peculiarities of any given reflex, such as its speed and rhythm of action.
Reactions in General
Though the reflex is simple by comparison with voluntary movements, it is not the simplest animal reaction, for it is cooerdinated and depends on the nervous system, while the simplest animals, one-celled animals, have no nervous system, any more than they have muscles or organs of any {40} kind. Without possessing separate organs for the different vital functions, these little creatures do nevertheless take in and digest food, reproduce their kind, and move. Every animal shows at least two different motor reactions, a positive or approaching reaction, and a negative or avoiding reaction.
The general notion of a reaction is that of a response to a stimulus. The stimulus acts on the organism and the organism acts back. If I am struck by a wave and rolled over on the beach, that is passive motion and not my reaction; but if the wave stimulates me to maintain my footing, then I am active, I respond or react.
Now there is no such thing as wholly passive motion. Did not Newton teach that "action and reaction are equal"?—and he was thinking of stones and other inanimate objects. The motion of a stone or ball depends on its own weight and shape and elasticity as much as on the blow it receives. Even the stone counts for something in determining its own behavior.
A loaded gun counts for more than a stone, because of the stored energy of the powder that is set free by the blow of the hammer. The "reaction" of the gun is greater than the force acting on it, because of this stored energy that is discharged.
An animal reaction resembles the discharge of the gun, since there is stored energy in the animal, consisting in the chemical attraction between food absorbed and oxygen inspired, and some of this energy is utilized and converted into motion when the animal reacts. The stimulus, like the trigger of the gun, simply releases this stored energy.
The organism, animal or human, fully obeys the law of conservation of energy, all the energy it puts out being accounted for by stored energy it has taken in in food and oxygen. But at any one time, when the organism receives {41} a stimulus, the energy that it puts forth in reaction comes from inside itself.
There is another way in which the organism counts in determining its reaction. Not only does it supply the energy of the response, but its own internal arrangements determine how that energy shall be directed. That is to say, the organism does not blow up indiscriminately, like a charge of dynamite, but makes some definite movement. This is true even of the simplest animals, and the more elaborate the internal mechanism of the animal, the more the animal itself has to do with the kind of response it shall make to a stimulus. The nervous system of the higher animals, by the connections it provides between the stimulus and the stores of energy in the muscles, is of especial importance in determining the nature of the response.
Stimuli are necessary to arouse the activity of the organism. Without any stimulus whatever, it seems likely that the animal would relapse into total inactivity. It should be said, however, that stimuli, such as that of hunger, may arise within the organism itself. The stimulus may be external or internal, but some stimulus is necessary in order to release the stored energy.
In general, then, a reaction consists in the release by a stimulus of some of the stored energy of an animal, and the direction of that energy by the animal's own internal mechanism of nerves and muscles (and, we may add, bones and sinews) into the form of some definite response.
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EXERCISES
1. Outline of the chapter, being at the same time a "completion test". Complete the following outline by filling in the blank spaces (usually a single word will fill the blank, but sometimes two words will be better):
A. Definition: A reaction is a response to a . The stimulus energy stored in the organism, and the has a definite form determined by the organism's own machinery of and .
B. Among very prompt reactions are the reflex and the "simple reaction". The reflex differs from the "simple reaction" in that:
(1) It usually takes less.
(2) It requires no___,
(3) The machinery for it is in the organism.
C. The machinery for a reflex consists of:
(1) a organ.
(2) a nerve.
(3) a nerve ,
(4) a nerve.
(5) a muscle or .
D. The sensory and motor nerves consist of __ which are branches of _. The cells for the motor nerves lie in the __, and those for the sensory nerves lie in two cases in the __, and in all other cases in bunches located close beside the __or __,
E. The neurone is the __ of which the nervous _ is composed. It consists of a __ and of two sorts of branches, the __ and the __. Internally, the neurone shows a peculiar structure of __ and __.
F. Communication from one neurone to another occurs across a called the synapse. The of an axon here comes into close contact with the or with the of another neurone. The communication takes place from the of the first neurone to the of the second.
G. The "nerve current" in a reflex therefore runs the following course: from the sense organ into a __ axon, along this to its __ in a nerve, and across a __ there into the __ of a neurone, and thence {43} out along the __of this neurone to the __or __ that executes the reflex. This is a two-neurone __, but often there is a third, __neurone between the __ and the ___.
H. Cooerdination is effected by the __ of the axons of the sensory and __ neurones, by which means the nerve current is _ to a team of __ and so to a team of __.
2. Is the reaction time experiment, as described in the text, an introspective or an objective experiment?
3. Mention two cases from common life that belong under the "simple reaction", two that belong under "choice reaction", and two that belong under the "associative reaction".
4. Arrange the reflexes mentioned in the text under the two heads of "protective" and "regulative".
5. Draw diagrams of (a) the neurone, (b) a synapse, (c) a reflex arc, and (d) a cooerdinated movement. Reduce each drawing to the simplest possible form, and still retain everything that is essential.
6. What part of the nervous system lies (a) in the forehead and top of the head, (b) in the very back of the head, (c) along the base of the skull, (d) within the backbone, (e) in the arm?
7. Using a watch to take the time, see how long it takes you to name the letters in a line of print, reading them in reverse order from the end of the line to the beginning. Compare with this time the time required to respond to each letter by the letter following it in the alphabet (saying "n" when you see m, and "t" when you see s, etc.). Which of these two "stunts" is more like reflex action, and how, nevertheless, does it differ from true reflex action?
8. The pupillary reflex. Describe the reaction of the pupil of the eye to light suddenly shining into the eye. This response can best be observed in another person, but you can observe it in yourself by aid of a hand mirror. On another person you can also observe the "crossed" pupillary reflex, by throwing the light into one eye only while you watch the other eye. What sort of connection do you suppose to exist between the two eyes, making this crossed reflex possible?
9. The lid reflex, or wink reflex, (a) Bring your hand suddenly close to another person's eye, and notice the response of the eyelid, (b) See whether you can get a crossed reflex here, (c) See whether your subject can voluntarily prevent (inhibit) the lid reflex, (d) See whether the reflex occurs when he gives the stimulus himself, by moving his own hand suddenly up to his eye. (e) What other stimulus, besides the visual one that you have been using, will arouse the same response?
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REFERENCES
C. Judson Herrick, in his Introduction to Neurology, 2nd edition, 1918, gives a fuller and yet not too detailed account of the neurone in Chapter III, and of reflex action in Chapter IV.
Percy G. Stiles, in his Nervous System and Its Conservation, 1915, discusses these matters in Chapters II, III and IV.
Ladd and Woodworth's Elements of Physiological Psychology, 1911, has chapters on these topics.
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CHAPTER III
REACTIONS OF DIFFERENT LEVELS
HOW SENSATIONS, PERCEPTIONS AND THOUGHTS MAY BE CONSIDERED AS FORMS OF INNER RESPONSE, AND HOW THESE HIGHER REACTIONS ARE RELATED IN THE NERVOUS SYSTEM TO THE SIMPLER RESPONSES OF THE REFLEX LEVEL.
Having defined a reaction as an act of the individual aroused by a stimulus, there is no reason why we should not include a great variety of mental processes under the general head of reactions. Any mental process is an activity of the organism, and it is aroused by some stimulus, external or internal; therefore, it is a reaction.
I hear a noise—now, while the noise, as a physical stimulus, comes to me, my hearing it is my own act, my sensory reaction to the stimulus. I recognize the noise as the whistle of a steamboat—this recognition is clearly my own doing, dependent on my own past experience, and may be called a perception or perceptive response. The boat's whistle reminds me of a vacation spent on an island—clearly a memory response. The memory arouses an agreeable feeling—an affective response, this may be called. In its turn, this may lead me to imagine how pleasant it would be to spend another vacation on that island, and to cast about for ways and means to accomplish this result—here we have imagination and reasoning, aroused by what preceded just as the sensation was aroused by the physical stimulus.
In speaking of any mental process as an act of the individual, we do not mean to imply that he is always conscious {46} of his activity. Sometimes he feels active, sometimes passive. He feels active in hard muscular work or hard thinking, while he feels passive in reflex action, in sensation, and in simply "being reminded" of anything without any effort on his own part. But he is active in everything he does, and he does everything that depends on his being alive. Life is activity, and every manifestation of life, such as reflex action or sensation, is a form of vital activity. The only way to be inactive is to be dead.
But vital activity is not "self-activity" in any absolute sense, for it is aroused by some stimulus. It does not issue from the individual as an isolated unit, but is his response to a stimulus. That is the sense of calling any mental process a reaction; it is something the individual does in response to a stimulus.
To call a sensation a form of reaction means, then, that the sensation is not something done to the person, nor passively received by him from outside, but something that he himself does when aroused to this particular form of activity. What comes from outside and is received by the individual is the stimulus, and the sensation is what he does in response to the stimulus. It represents the discharge of internal stored energy in a direction determined by his own inner mechanism. The sensation depends on his own make-up as well as on the nature of the stimulus, as is especially obvious when the sensation is abnormal or peculiar. Take the case of color blindness. The same stimulus that arouses in most people the sensation of red arouses in the color-blind individual the sensation of brown. Now what the color-blind individual receives, the light stimulus, is the same as what others receive, but he responds differently, i.e., with a different sensation, because his own sensory apparatus is peculiar. |
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