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Psychology - A Study Of Mental Life
by Robert S. Woodworth
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We say that a fact is recalled when we think of it without its being present to the senses. While the original {368} observation of the fact was a response to a sensory stimulus, the recall of it is a response to some other stimulus, some "substitute stimulus". When John is before me, I observe that his eyes are brown in response to a visual stimulus; but I later recall this fact in response simply to the name "John", or in response to the question as to what is the color of John's eyes. I see what a square is by seeing squares and handling them, and later I get this idea simply in response to the word "square" in conversation or reading.

Memory Images

Now, can sensations be recalled, can they be aroused except by their natural sensory stimuli? Can you recall the color blue, or the sound of a bugle, or the odor of camphor, or the feel of a lump of ice held in the hand? Almost every one will reply "Yes" to some at least of these questions. One may have a vivid picture of a scene before the "mind's eye", and another a realistic sound in the "mind's ear", and they may report that the recalled experience seems essentially the same as the original sensation. Therefore, sensory reactions are no exception to the rule of recall by a substitute stimulus.

A sensation or complex of sensations recalled by a substitute stimulus is called a "mental image" or a "memory image".

Individuals seem to differ in the vividness or realism of their memory images—the likeness of the image to an actual sensation—more than in any other respect. Galton, in taking a sort of census of mental imagery, asked many persons to call up the appearance of their breakfast table as they had sat down to it that morning, and to observe how lifelike the image was, how complete, how adequate in respect to color, how steady and lasting, and to compare {369} the image in these respects with the sensory experience aroused by the actual presence of the scene. Some individuals reported that the image was "in all respects the same as an original sensation", while others denied that they got anything at all in the way of recalled sensation, though they could perfectly well recall definite facts that they had observed regarding the breakfast table. The majority of people gave testimony intermediate between these extremes.

Individuals differ so much in this respect that they scarcely credit each other's testimony. Some who had practically zero imagery held that the "picture before the mind's eye" spoken of by the poets was a myth or mere figure of speech; while those who were accustomed to vivid images could not understand what the others could possibly mean by "remembering facts about the breakfast table without having any image of it", and were strongly tempted to accuse them of poor introspection, if not worse. It is true that in attempting to study images, we have to depend altogether on introspection, since no one can objectively observe another person's memory image, and therefore we are exposed to all the unreliability of the unchecked introspective method. But at the same time, when you cross-question an individual whose testimony regarding his imagery is very different from yours, you find him so consistent in his testimony and so sure he is right, that you are forced to conclude to a very real difference between him and yourself. You are forced to conclude that the power of recalling sensations varies from something like one hundred per cent, down to practically zero.

Individuals may also differ in the kind of sensation that they can vividly recall. Some who are poor at recalling visual sensations do have vivid auditory images, and others who have little of either visual or auditory imagery call up {370} kinesthetic sensations without difficulty. When this was first discovered, a very pretty theory of "imagery types" was built upon it. Any individual, so it was held, belonged to one or another type: either he was a "visualist", thinking of everything as it appears to the eyes, or he was an "audile", thinking of everything according to its sound, or he was a "motor type", dealing wholly in kinesthetic imagery, or he might, in rare cases, belong to the olfactory or gustatory or tactile type.



But the progress of investigation showed, first, that a "mixed type" must also be admitted, to provide for individuals who easily called up images of two or more different senses; and, later on, that the mixed type was the most common. In fact, it is now known to be very unusual for an individual to be confined to images of a single sense. Nearly every one gets visual images more easily and frequently than those of any other sense, but nearly every one has, from time to time, auditory, kinesthetic, tactile and olfactory images. So that the "mixed type" is the only real type, the extreme visualist or audile, etc., being exceptional and not typical.

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Limitations of Imagery

Recalled sensations are commonly inferior to their originals, both in the enjoyment they afford and in the use that can be made of them. They are likely to be inferior in several respects.

(1) An image has usually less color, or tone—less body, realism and full sensory quality—than a sensation aroused by its appropriate peripheral stimulus. While you may be able to call up a fairly good image of your absent friend's face, the actual presence of your friend would be more satisfactory, just as a sensory experience. You may be able to run over a piece of music "in your head", and if your auditory imagery is strong you may even run over an orchestral piece, and get the tone quality of the various instruments; but, after all, such a mental concert is an imperfect substitute for a real orchestra. You enjoy a real whiff of the sea more than the best olfactory image you can summon. There is something lacking in these recalled sensations, and the trouble seems to be that they are not sensations enough; they lack sensory body.

(2) Images are apt to be sketchy and lacking in detail, and also narrow and lacking in background.

(3) Images are apt to be unsteady and fleeting, as compared with actual sensations. Where the peripheral stimulus, continuing, keeps the sensation going, the substitute stimulus that recalls a sensation is not so effective in this respect, any more than in giving body and detail. In all these respects, an image is less enjoyable and satisfying than an actual sensation.

(4) On the more practical side, images are inferior to the actual presence of an object, in that we cannot utilize the image as a source of new information. {372} We cannot observe facts in the image of a thing that we have not observed in the actual presence of the thing.

At one of the universities, there is a beautiful library building, with a row of fine pillars across the front, and the students pass this building every day and enjoy looking at it. It has long been a favorite experiment in the psychology classes at that university to have the students call up an image of the library, and to have them state how clear their image is, how complete and how vivid. Then they are asked to count the pillars from their image, and to tell what kind of capitals the pillars have, and whether the shafts are plain or fluted. But at this point the students begin to object. "We have never counted those pillars, and cannot be expected to know the number now." In fact, few of them give the correct number, and those who have reported clear and vivid images are little better off in this respect than those whose images are dim and vague.

The image, then, does not give you facts that you did not observe in the presence of the object. The substitute stimulus, which now recalls the image, only recalls responses which you made when the real object was the stimulus. If you looked at the object simply to get its general appearance, the general appearance is all you can recall. If you noted the color of the object, you can probably recall the color. If you noted such details as the number of pillars, you can recall these details. But the substitute stimulus that now arouses the image is by no means the equivalent of the original peripheral stimulus in making possible a variety of new reactions. Its only linkage is with reactions actually made by you in response to the real object. The substitute stimulus, such as the name of a building, became linked with responses actually made by you, not with responses that you simply might have made, when the object was present. This important fact is closely related to the {373} unreliability of testimony that was mentioned before under the head of "unintentional memory". [Footnote: See pp. 346-348.] Facts recalled are facts previously observed.

It is true, of course, that recalled facts can be compared and new facts be observed by the comparison. We may recall how John looks, and how James looks, and note the fact, not previously observed, that they look alike. A great deal can be inferred in this way by a person who is sitting in his room far from the objects thought about. But this noting of the relationships of different objects is a very different matter from observing what is there, in a single object or scene. What is there can only be observed when you are there.

The Question of Non-Sensory Recall

Many observed facts are not strictly facts of sensation, though observed by means of the senses. Let us suppose, for an example, that your attention is caught by the bright green new leaves at the tips of the branches of an evergreen tree in summer, and that you notice also the darker green of the older leaves further back along the branches, and, exploring deeper, find leaves that are dead and brown, while still further in they have all fallen off, leaving bare branches reaching back to the trunk; so that you finally "see" how the tree is constructed, as a hollow cone of foliage supported by an interior framework of branches. All this has meant a lot of different reactions on your part, and the final "seeing" of how the tree is constructed would scarcely be called a sensation, since it has required mental work beyond that of simply seeing the tree. It is a response additional to the strictly sensory response of seeing the tree.

Now the question is whether this additional response can be recalled, without recalling at the same time the primary {374} response of seeing the tree. Can we recall the fact observed about the tree without at the same time seeing the tree "in the mind's eye"? Must we necessarily have an image of the tree when we recall the way the tree is constructed?

Since getting the general sensory appearance of the tree, and observing the way it is constructed, are two different responses, it seems quite conceivable that either fact should be recalled without the other; and no one doubts that the sensory appearance of the tree can be recalled without the other observed fact coming up along with it. But many authorities have held that the non-sensory fact could not be recalled alone; in other words, they have held that every recalled fact comes as a sensory image, or with a sensory image. Persons with ready visual imagery are of course likely to get a visual image with any fact they may recall. But persons whose visual imagery is hard to arouse say that they recall facts without any visual image. I who write these words, being such a person, testify that while I have been writing and thinking about that tree I have not seen it before my mind's eye.

It is true, however, that I have had images during this time—auditory images of words expressing the facts mentioned. Another individual might have had kinesthetic images instead of either visual or auditory. But can there be a recall of fact without any sensory image?

On this question, which has been called the question of "imageless thought", though it might better be called that of "imageless recall", controversy has raged and is not yet at rest, so that a generally accepted conclusion cannot be stated. But the best indications are to the effect, first, that vague and fleeting images, especially of the kinesthetic sort, are often present without being detected except by very fine introspection, some image being pretty sure to come up every few seconds when we are engaged in silent thought or {375} recall; but, second, that images are not present every second of the time, and that at the instant when a non-sensory fact is recalled it is apt to be alone.

Hallucinations

Since a vivid mental image may be "in all respects the same as an actual sensation", according to the testimony of some people, the question arises how, then, an image is distinguished from a sensation. Well, the image does not usually fit into the objective situation present to the senses. But if it does fit, or if the objective situation is lost track of, then, as a matter of fact, the image may be taken for a sensation.

You see some beautiful roses in the florist's window, and you smell them; the odor fits into the objective situation very well, till you notice that the shop door is shut and the window glass impervious to odors, from which you conclude that the odor must have been your image.

You are lost in thought of an absent person, till, forgetting where you are, you seem to see him entering the door; he "fits" well enough for an instant, but then the present situation forces itself upon you and the image takes its proper place.

You are half asleep, almost lost to the world, and some scene comes before you so vividly as to seem real till its oddity wakens you to the reality of your bedroom. Or you are fully asleep, and then the images that come are dreams and seem entirely real, since contact with the objective situation has been broken.

Images taken for real things are common in some forms of mental disorder. Here the subject's hold on objective fact is weakened by his absorption in his own desires and fears, and he hears reviling voices and smells suspicious {376} odors or sees visions that are in line with his desires and fears.

Such false sensations are called "hallucinations". An hallucination is an image taken for a sensation, a recalled fact taken for a present objective fact. It is a sensory response, aroused by a substitute stimulus, without the subject's noticing that it is thus aroused instead of by its regular peripheral stimulus.

Synesthesia.

Quite a large number of people are so constituted as to hear sounds as if colored, a deep tone perhaps seeming dark blue, the sound of a trumpet a vivid red, etc. Each vowel and even each consonant may have its own special color, which combine to give a complex color scheme for a word. Numbers also may be colored. This colored hearing is the commonest form of "synesthesia", which consists in responding to a stimulus acting on one sense, by sensations belonging to a different sense. Whether the persons so constituted as to respond in this way are constituted thus by nature or by experience is uncertain, though the best guess is that the extra sensations are images that have become firmly attached to their substitute stimuli during early childhood.

Free Association

Mental processes that depend on recall are called "associative processes", since they make use of associations or linkages previously formed. When some definite interest or purpose steers the associative processes, we speak of "controlled association", contrasting this with the "free association" that occurs in an idle mood, when one thought simply calls up another with no object in view and no more than fleeting desires to give direction to the sequence of thoughts.

Revery affords the best example of free association. I {377} see my neighbor's dog out of my window, and am reminded of one time when I took charge of that dog while my neighbor was away, and then of my neighbor's coming back and taking the dog from the cellar where I had shut him up; next of my neighbor's advice with respect to an automobile collision in which I was concerned; next of the stranger with whom I had collided, and of the stranger's business address on the card which he gave me; next comes a query as to this stranger's line of business and whether he was well-to-do; and from there my thoughts switch naturally to the high cost of living.

This is rather a drab, middle-aged type of revery, and youth might show more life and color; but the linkages between one thought and the next are typical of any revery. The linkages belong in the category of "facts previously observed". I had previously observed the ownership of this dog by my neighbor, and this observation linked the dog and the neighbor and enabled the dog to recall the neighbor to my mind. Most of the linkages in this revery are quite concrete, but some are rather abstract, such as the connection between being well-to-do (or not) and the high cost of living; but, concrete or abstract, they are connections previously observed by the subject. Sometimes the linkage keeps the thoughts within the sphere of the same original experience, and sometimes switches them from one past experience to another, or even away from any specific past experience to general considerations; yet always the linkage has this character, that the item that now acts as stimulus has been formerly combined in observation with the other item that now follows as the response. One fact recalls another when the two have been previously observed as belonging together.

But suppose, as is commonly the case, that the fact now present in my mind has been linked, in different past {378} experiences, with several different facts. Then two questions demand our attention: whether all these facts are recalled; and, if not, what gives the advantage to the fact actually recalled over the others that are not recalled.

The answer to the first question is plain. The fact first present in mind does not call up all the associated facts, but usually only one of them, or at least only one at a time. My neighbor, in the example given, though previously associated with a dozen other facts, now calls up but two of these facts, and those two not simultaneously but one after the other. We see a law here that is very similar to a law stated under the head of attention. There, we said that of all the objects before us that might be noticed only one was noticed at a time; and here we say that of all the objects that might be recalled to mind by association only one is recalled at a time. Both statements can be combined into the one general "law of reaction" which was mentioned before, that of all the responses linked to a given stimulus (or complex of stimuli) only one is actually aroused at the same instant, though several may be aroused in succession, provided the stimulus continues.

In revery, the stimulus usually does not continue. The first fact thought of gives way to the fact that it recalls, and that to one that it recalls in turn, and so on, without much dwelling on any fact. But if we do dwell on any fact—as upon the thought of a certain person—then this stimulus, continuing to act, calls up in succession quite a number of associated facts.

If, then, only one of the several facts associated with the stimulus is recalled at once, our second question presents itself, as to what are the factors of advantage that cause one rather than another of the possible responses to occur. The fact first in mind might have called up any one of several facts, having been linked with each of them in past {379} experience; and we want to know why it recalls one of these facts rather than the rest.

The factors of advantage in recall are the factors that determine the strength of linkage between two facts; and they are:

the frequency with which the linkage has occurred; the recency with which it has occurred; and the intensity with which it has occurred.

If I have frequently observed the connection of two facts, the linkage between them is strong; if I have recently observed their connection, the linkage between them is strong till the "recency value" dies away; and if my observation of the connection of the two facts was a vivid experience, or intense reaction, then, also, the linkage between them is strong. If these three factors of advantage work together in favor of the same response, then that response is sure to occur; but if the three factors pull different ways, we should have to figure out the balance of advantage before we could predict which of the possible responses would actually be made. Naturally enough, even the skilful psychologist is often unable to strike the balance between the three factors. He does know, however, and all of us know in a practical way, that strong recency value offsets a lot of frequency; so that a mere vague allusion to a very recent topic of conversation can be depended on to recall the right facts to the hearer's mind, even though they lie outside of his habitual line of interest. "James", by virtue of frequency, means your brother or friend; but after the lecturer has been talking about the psychologist James, repetition of this name infallibly recalls the psychologist to mind.

Besides frequency, recency and intensity, there is, indeed, another factor to be taken into account; and that is the {380} present state of the subject's mind. If he is unhappy, unpleasant associations have the advantage; if happy, pleasant. If he is absorbed in a given matter, facts related to that matter have the advantage. Frequency, recency and intensity summarize the history of associations, and measure their strength as dependent on their history; but the present state of mind is an additional directive factor, and when it has much to do with recall, we speak of directed or controlled association.

Before we pass to the topic of controlled association, however, there is another form of free association, quite different from revery, to be examined. There is an experiment, called the free association test, in which the subject is given a series of words as stimuli, and is asked to respond to each word by speaking some other word, the first that is recalled by the stimulus. No special kind of word need be given in response, but simply the first word recalled. Though this is called free association, it is controlled to the extent that the response must be a word, and the result is very different from revery. Instead of the recall of concrete facts from past experience, there is recall of words. If you give the subject the stimulus word, "table", his response is "chair" or "dinner", etc., and often he does not think of any particular table, but simply of the word. Words are so often linked one with another that it is no wonder that one recalls another automatically. What particular word shall be recalled depends on the frequency, recency and intensity of past linkage.

Though this form of test seems so simple as almost to be silly, it is of use in several ways. When a large number of stimulus words are used, and the responses classified, some persons are found to favor linkages that have a personal significance—"egocentric responses", these are called—while other persons run to connections that are {381} impersonal and objective. Thus the test throws some light on the individual's habits of attention. The test has also a "detective" use, based upon the great efficacy of the factor of recency; you may be able by it to tell whether an individual has recently had a certain matter in mind. If he happens to be an individual who has recently committed some crime, properly selected stimulus words will lead him to recall the scene of the crime, and thus to make responses that betray him, unless he checks them and so arouses suspicion by his hesitation. Another use of the test is for unearthing a person's emotional "complexes", which of course possess a high intensity value. If the subject shows hesitation and embarrassment in responding to words referring to money, the indication is that he is emotionally disturbed over the state of his finances. One person who consulted a doctor for nervousness made peculiar responses to stimulus words relating to the family, and was discovered to be much disturbed over his family's opposition to his projected marriage. The free association test is useful rather as giving the experienced psychologist hints to be followed up than as furnishing sure proof of the contents of the subject's mind.

Controlled Association

There is a controlled association test conducted like this one in free association, except that the subject is required to respond to each stimulus word by a word standing in a specified relation to it. To one series of words he must respond by saying their opposites; to another, by mentioning a part of each object named; to another series, consisting of names of countries, he must respond by naming as quickly as possible the capital of each country named; and there are many tests of this sort, each dealing with some class of relationships which, being often observed, are easily handled {382} by a person of normal intelligence. The intelligent subject makes few errors in such a test, and responds in very quick time. Indeed, the remarkable fact is that he takes less time to respond in an easy controlled association test than in the free association test; which shows that the "control" acts not simply to limit the response, but also to facilitate it.

The "control" here is often called by the name of "mental set". It is a good example of a "reaction tendency". On being told you are to give opposites, you somehow set or adjust your mental machinery for making this type of response. The mental set thus thrown into action facilitates responses of the required type, while inhibiting other responses that would readily occur in the absence of any directive tendency. If the word "good" came as a stimulus word in a free association test, it might easily arouse the responses, "good day", "good night", "good boy", "good better", and many besides, since all of these combinations have been frequently used in the past; and the balance of frequency, recency and intensity might favor any one of these responses. But when the subject is set for opposites, the balance of these factors has little force as against the mental set. The mental set for opposites favors the revival of such combinations as "new—old", "good—bad", and such others of this class as have been noted and used in the subject's past experience.

Mental set is a selective factor, a factor of advantage. It does not supersede the previously formed associations, or work independently of them, but selects from among them the one which fits the present task. Does it get in its work after recall has done its part, or before? Does it wait till recall has brought up a number of responses, and then pick out the one that fills the bill? No, it often works much too quickly for that, giving the right response instantly; and introspection is often perfectly clear that none but the right {383} response is recalled at all. The selective influence of the mental set is exerted before recall; it facilitates the right recall and inhibits recall of any but the right response.

In controlled association, as in free association, only one of the facts previously linked with the stimulus is recalled at a time; but while in free association the factors of frequency, recency and intensity of past linkage determine which of the many possible facts shall be recalled, in controlled association the additional factor of mental set is present and has a controlling influence in determining which fact shall be recalled. Thus, in an opposites test, the stimulus word "good" promptly calls up the pair "good—bad", because the mental set for opposites gives this response a great advantage over "good night" and other responses which may have a very strong linkage with the stimulus word.

The mental set is itself a response to a stimulus. It is an inner response thrown into activity by some stimulus, such as the stimulus of being asked to give the opposites of a series of words that are presently to be shown or spoken. This inner response of getting ready for the task can be introspectively observed by a person who is new to this type of test. It may take the form of mentally running over examples of opposites—or whatever kind of responses are to be called for—or it may take the form of calling up some image or diagram or gesture that symbolizes the task. A visual image of the nose on the face may serve as a symbol of the part-whole relationship, a small circle inside a larger one may symbolize the relation of an object to a class of objects, and gesturing first to the right and then to the left may symbolize the relationship of opposites. But as the subject grows accustomed to a given task, these conscious symbols fade away, and nothing remains except a general "feeling of readiness" or of "knowing what you are {384} about". The mental set remains in force, however, and is no less efficient for becoming almost unconscious.

Examples of Controlled Association

Dwelling so long on the test for controlled association may have created the impression that this is a rather artificial and unusual type of mental performance; but in reality controlled association is a very representative mental process, and enters very largely into all forms of mental work. This is true in arithmetical work, for example. A pair of numbers, such as 8 and 3, has been linked in past experience with several responses; it means 83, it means 11, it means 5, and it means 24. But if you are adding, it means 11, and no other response occurs; if you are multiplying, it means 24, and only that response occurs. The mental set for multiplying facilitates the responses of the multiplication table and inhibits those of the addition table, while the mental set for adding does the reverse. Rapid adding or multiplying would be impossible without an efficient mental set. Thus in arithmetic, as in the tests, the mental set is an inner response to the task.

In reading, there is a mental set which is an inner response to the context, and which determines which of the several well-known meanings of a word shall actually be called to mind when the word is read. Presented alone, a word may call up any of its meanings, according to frequency, etc.; but in context it usually brings to mind just the one meaning that fits the context. The same is true of conversation.

The objective situation arouses a mental set that controls both thought and action. The situation of being in church, for example, determines the meanings that are got from the words heard, and controls the motor behavior to {385} fit the occasion. The subject, observing the situation, adjusts himself to it, perhaps without any conscious effort, and his adjustment facilitates appropriate mental and motor reactions, while inhibiting others.

A problem arouses a mental set directed towards solution of the problem. A difficult problem, however, differs from a context or familiar task or situation in this important respect, that the appropriate response has not been previously linked with the present stimulus, so that, in spite of ever so good a mental set, the right response cannot immediately be recalled. One must search for the right response. Still, the mental set is useful here, in directing the search, and keeping it from degenerating into an aimless running hither and thither. Problem solution is so different a process from smooth-running controlled association that it deserves separate treatment, which will be given it a few chapters further on, under the caption of reasoning.

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EXERCISES

1. Outline the chapter.

2. The rating of images belonging under different senses. Try to call up the images prescribed below, and rate each image according to the following scale:

3. . . . The image is practically the same as a sensation, as bright, full, incisive, and, in short, possessed of genuine sensory quality.

2. . . . The image has a moderate degree of sensory quality.

1. . . . The image has only faint traces of sensory quality.

0. . . . No sensory image is called up, though there was a recall of the fact mentioned.

Call up visual images of: a friend's face, a sun flower, a white house among trees, your own signature written in ink.

Call up auditory images of: the sound of your friend's voice, a familiar song, an automobile horn, the mewing of a cat.

Call up olfactory images of: the odor of coffee, of new-mown hay, of tar, of cheese.

Call up gustatory images of: sugar, salt, bitter, acid.

Call up cutaneous images of: the feel of velvet, a lump of ice, a pencil held against the tip of your nose, a pin pricking your finger.

Call up kinesthetic imagery of: lifting a heavy weight, reaching up to a high shelf, opening your mouth wide, kicking a ball.

Call up organic imagery of: feeling hungry, feeling thirsty, feeling nausea, feeling buoyant.

In case of which sense do you get the most lifelike imagery, and in case of which sense the least. By finding the average rating given to the images of each sense, you can arrange the senses in order, from the one in which your imagery rates highest to the one in which it rates lowest. It may be best to try more cases before reaching a final decision on this matter.

3. Verbal imagery. When you think of a word, do you have a visual, auditory, or kinesthetic image of it—or how does it come?

4. In reading, notice how much imagery of objects, persons, scenes, sounds, etc., occurs spontaneously.

5. Analysis of a revery. Take any object as your starting point, and let your mind wander from that wherever it will for a minute. {387} Then review and record the series of thoughts, and try to discover the linkages between them.

6. Free association experiment. Respond to each one of a list of disconnected words by saying the first word suggested by it. Use the following list: city, war, bird, potato, day, ocean, insect, mountain, tree, roof.

7. Controlled association, (a) Use the same list of stimulus words as above, but respond to each by a word meaning the opposite or at least something contrasting, (b) Repeat, naming a part of the object designated by each of these same words, (c) Repeat again, naming an instance or variety of each of the objects named. Did you find wrong responses coming up, or did the mental set exclude them altogether?

8. Write on a sheet of paper ten pairs of one-place numbers, each pair in a little column with a line drawn below, as in addition or multiplication examples. See how long it takes you to add, and again how long it takes to multiply all ten. Which task took the longer, and why? Did you notice any interference, such as thinking of a sum when you were "set" for products?

9. Free association test for students of psychology. Respond to each of the following stimulus words by the first word suggested by it of a psychological character:

conditioned objective gregarious delayed correlation fear negative end-brush mastery rat pyramidal submission stimulus semicircular feeling-tone substitute kinesthetic primary axon advantage tension synapse field blend autonomic quotient rod retention limit fovea nonsense apraxia saturated higher thalamus red-green paired organic complementary economy tendency after exploration preparatory basilar recency native fluctuation curve endocrine dot perseveration expressive Binet synesthesia James-Lange frontal facilitation flexion overlapping

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REFERENCES

On imagery, synesthesia, etc., see Gallon's Inquiries into Human Faculty and Its Development, 1883, pp. 57-112; and for more recent studies of imagery see G. H. Betts on The Distribution and Function of Mental Imagery, 1909, and Mabel R. Fernald on The Diagnosis of Mental Imagery, 1912.

On the diagnostic use of the association test, an extensive work is that of C. G. Jung, Studies in Word-Association, translated by Eder, 1919.

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CHAPTER XVI

THE LAWS OF ASSOCIATION

AN ATTEMPT TO REDUCE THE LEARNING PROCESS TO ITS ELEMENTS

This is a very serious occasion. What we now have before us is one of the great outstanding problems of psychology, a problem that has come down through the ages, with succeeding generations of psychological thinkers contributing of their best to its solution; and our task is to attack this problem afresh in the light of modern knowledge of the facts of learning and memory. We wish to gather up the threads from the three preceding chapters, which have detailed many facts regarding learned reactions of all sorts, and see whether we cannot summarize our accumulated knowledge in the form of a few great laws. We wish also to relate our laws to what is known of the brain machinery.

The Law of Exercise

Of one law of learning, we are perfectly sure. There is no doubt that the exercise of a reaction strengthens it, makes it more precise and more smooth-running, and gives it an advantage over alternative reactions which have not been exercised. Evidence for these statements began to appear as soon as we turned the corner into this part of our subject, and has accumulated ever since. This law is sometimes called the "law of habit", but might better be called the "law of improvement of a reaction through exercise", or, more briefly, the "law of exercise".

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The law of exercise is very broad in its scope, holding good of life generally and not alone of mental life. Exercise of a muscle develops the muscle, exercise of a gland develops the gland; and, in the same way, exercise of a mental reaction strengthens the machinery used in making that reaction.

Let us restate the law in terms of stimulus and response. When a given stimulus arouses a certain response, the linkage between that stimulus and that response is improved by the exercise so obtained, and thereafter the stimulus arouses the response more surely, more promptly, more strongly than before.

Under the law of exercise belong several sub-laws already familiar to us.

1. The law of frequency refers to the cumulative effect of repeated exercise. The practice curve gives a picture of this sub-law, showing how improvement with repeated exercise of a performance is rapid at first and tapers off into the physiological limit, beyond which level more repetition cannot further improve the performance. The superiority of "spaced study" over unspaced means that exercise is more effective when rest periods intervene between the periods of exercise; as this is notoriously true of muscular exercise, it is not surprising to find it true of mental performances as well.

2. The law of recency refers to the gradual weakening of the machinery for executing a reaction when no longer exercised; it is the general biological law of "atrophy through disuse" applied to the special case of learned reactions. As exercise improves the linkage between stimulus and response, so disuse allows the linkage to deteriorate. This law is pictured more completely and quantitatively in the curve of forgetting.

Really, there are two laws of recency, the one being a {391} law of retention, the other a law of momentary warming up through exercise. The law of retention, or of forgetting, is the same as atrophy through disuse. The warming-up effect, well seen in the muscle which is sluggish after a long rest but becomes lively and responsive after a bit of exercise, [Footnote: See p. 73.] appears also in the fact that a skilled act needs to be done a few times in quick succession before it reaches its highest efficiency, and in the fact of "primary memory", the lingering of a sensation or thought for a few moments after the stimulus that aroused it has ceased. Primary memory is not strictly memory, since it does not involve the recall of facts that have dropped out of mind, but just a new emphasis on facts that have not yet completely dropped out. Warming up is not a phenomenon of learning, but it is a form of recency, and is responsible for the very strong "recency value" that is sometimes a help in learning, [Footnote: See p. 345.] and sometimes a hindrance in recall. [Footnote: See p. 356.]

3. The law of intensity simply means that vigorous exercise strengthens a reaction more than weak exercise. This is to be expected, but the question is, in the case of mental performances, how to secure vigorous exercise. Well, by active recitation as compared with passive reception, by close attention, by high level observation. In active recitation, the memorizer strongly exercises the performance that he is trying to master, while in reading the lesson over and over he is giving less intense exercise to the same performance.

The Law of Effect

We come now to a law which has not so accepted a standing as the law of exercise, and which may perhaps be another sub-law under that general law. The "law of effect" may, however, be regarded simply as a generalized statement of {392} the facts of learning by trial and error. The cat, in learning the trick of escaping from a cage by turning the door-button, makes and therefore exercises a variety of reactions; and you might expect, then, in accordance with the law of exercise, that all of these reactions would be more and more firmly linked to the cage-situation, instead of the successful reaction gradually getting the advantage and the unsuccessful being eliminated. The law of effect, stated as objectively as possible, is simply that the successful or unsuccessful outcome or effect of a reaction determines whether it shall become firmly linked with the stimulus, or detached from the stimulus and thus eliminated. The linkage of a response to a stimulus is strengthened when the response is a success, and weakened when the response is a failure.

Success here means reaching the goal of an awakened desire or reaction-tendency, and failure means being stopped or hindered from reaching the goal. Since success is satisfying and failure unpleasant, the law of effect is often stated in another form: a response that brings satisfaction is more and more firmly attached to the situation and reaction-tendency, while a response that brings pain or dissatisfaction is detached.

The law of effect is a statement of fact, but the question is whether it is an ultimate fact, or whether it can be explained as a special case of the law of exercise. Some have suggested that it is but a special case of the sub-law of frequency; they call attention to the fact that the successful response must be made at every trial, since the trial continues till success is attained, whereas no one unsuccessful response need be made at every trial; therefore in the long run the successful response must gain the frequency advantage. But there is a very ready and serious objection to this argument; for it may and does happen that an unsuccessful response is repeated several times during a single {393} trial, while the successful response is never made more than once in a single trial, since success brings the trial to a close; and thus, as a matter of fact, frequency often favors the unsuccessful response—which, nevertheless, loses out in competition with the successful response.

Can the law of effect be interpreted as an instance of the sub-law of recency? The successful reaction always occurs at the end of a trial, and is the most recent reaction at the beginning of the next trial. This recency might have considerable importance if the next trial began instantly (as in unspaced learning), but can have no importance when so long as interval as a day is left between trials; for evidently the recency of twenty-four hours plus ten seconds is not effectively different from that of an even twenty-four hours. Recency, then, does not explain the law of effect.

Can it be explained as an instance of the sub-law of intensity? An animal, or man, who sees success coming as he is making the reaction that leads directly to success, throws himself unreservedly into this reaction, in contrast with his somewhat hesitant and exploratory behavior up to that time. The dammed-up energy of the reaction-tendency finds a complete outlet into the successful reaction, and therefore the successful reaction is more intensely exercised than the unsuccessful. This seems like a pretty good explanation, though perhaps not a complete explanation.

Limitations of the Law of Exercise

The law of exercise, with all its sub-laws, is certainly fundamental and universal; it is always in operation whenever anything is learned; and yet, just by itself, it goes only halfway towards accounting for learned reactions. For a reaction to be exercised, it must be made, and the law of exercise presupposes that it is made, and does not attempt to account for its being made in the first place.

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The law of exercise does not cover the formation of new linkages, but only the strengthening of linkages that are already working. It does not explain the attachment of a response to some other than its natural stimulus, nor the combination, of responses into a higher unit, nor the association of two facts so that one later recalls the other. We learn by doing, but how can we do anything new so as to start to learn? We learn by observing combinations of facts, but how in the first place do we combine the facts in our minds?

How, for example, can we learn to respond to the sight of the person by saying his name? Evidently, by exercising this linkage of stimulus and response. But how did we ever make a start in responding thus, since there is nothing about the person's looks to suggest his name? The name came to us through the ear, and the face by way of the eye; and if we repeated the name, that was a response to the auditory stimulus and not to the visual. How has it come about, then, that we later respond to the visual stimulus by saying the name?

In short, the more seriously we take the law of exercise, the more we feel the need of a supplementary law to provide for the first making of a reaction that then, by virtue of exercise, is strengthened.

This is the problem that occupied the older writers on psychology when they dealt with "association"; and their solution of the problem was formulated in the famous "laws of association". The laws of association were attempts to explain how facts got associated, so that later one could recall another.

These laws have a long history. From Aristotle, the ancient Greek who first wrote books on psychology, there came down to modern times four laws of association. Facts become associated, according to Aristotle, when they are {395} contiguous (or close together) in space, or when they are contiguous in time, or when they resemble each other, or when they contrast with each other. The psychologists of the earlier modern period, in the eighteenth and first part of the nineteenth centuries, labored with very good success to reduce these four laws to one comprehensive law of association. Contiguity in space and in time were combined into a law of association by contiguity in experience, since evidently mere physical contiguity between two objects could establish no association between them in any one's mind except as he experienced them together.

Association by Similarity

Continuing their simplification of the laws of association, these older psychologists showed that resemblance and contrast belonged together, since to be similar things must have something in common, and to be contrasted also two things must have something in common. You contrast north with south, a circle and a square, an automobile and a wheelbarrow; but no one thinks of contrasting north with a circle, south with an automobile, or a square and a wheelbarrow, though these pairs are more incongruous than the others. Things that are actually associated as contrasting with each other have something in common; and therefore association by contrast could be included under association by similarity. Thus the four laws had been reduced to two, association by contiguity and association by similarity.

The final step in this reduction was to show that association by similarity was a special case of association by contiguity. To be similar, two things must have something in common, and this common part, being contiguous with the remainder of each of the two things, establishes an indirect contiguity between the two things, a {396} sort of contiguity bridge between them. One thing has the parts or characteristics, A B X Y, and the similar thing has the parts or characteristics, C D X Y; and thus X Y, when seen in the second thing, call up A B, with which they are contiguous in the first thing.

A stranger reminds me of my friend because something in the stranger's face or manner has been met with before in my friend; it has been contiguous with my friend, and recalls him by virtue of this contiguity. The stranger, as a whole individual, has never been contiguous with my friend, but some characteristic of the stranger has been thus contiguous. In association by similarity, it is not the whole present object that arouses recall of the similar object, but some part of the present object. This kind of association is important in thinking, since it brings together facts from different past experiences, and thus assembles data that may be applied to a new problem. If every new object or situation could only be taken as a whole, it could not remind me of anything previously met; and I should be like an inexperienced child in the presence of each new problem; but, taken part by part, the novel situation has been met with before, and can be handled in the light of past experience.

Exactly what there is in common between two similar faces or other objects cannot always be clearly made out; but the common characteristic is there, even if not consciously isolated, and acts as an effective stimulus to recall.

Association by Contiguity

This reduction of all the laws of association to one great law was no mean achievement; and the law of association by contiguity in experience holds good. If one thing recalls another to your mind, you can be sure that the two {397} have been contiguous in your experience, either as wholes or piecemeal. For two things to become associated, they must be experienced together.

Yes, the law holds good, when thus stated—but notice that the statement is virtually negative. It says, in effect, that two things do not become associated unless they are contiguous in experience. If it were turned about to read that two things do become associated if they are contiguous in experience, it would no longer be a true law, for the exceptions would then be extremely numerous.

The memory and testimony experiments have brought many exceptions to light. Show a person twenty pictures in a row, and let him examine each one in turn so closely that he can later recognize every one of them; and still he will not have the adjacent pictures so associated that each one can call up the next in order. To accomplish his last task, he has to observe the order specifically; it is not enough that he simply experiences pictures together. Or, again, read to a person twenty pairs of words, asking him to notice the pairs so that later he can respond by the second word of any pair when the first word is given him; and read the list through three or four times, so that he shall be able to make almost a perfect score in the expected test; still he will have formed few associations between the contiguous pairs, and will make a very low score if you ask him to recite the pairs in order. Many similar experiments have yielded the same general result—contiguity in experience and still no association.

The law of association by contiguity is unsatisfactory from a modern standpoint because it treats only of the stimulus, and says nothing about the response. It states, quite truly, that stimuli must be contiguous in order that an association between them may be formed, but it neglects to state that the association, being something in us, must {398} be formed by our reaction to the stimuli. It is especially necessary to consider the response because, as we have just seen, the response is not always made and the association, therefore, not always formed. Only if the stimuli are contiguous, can the associating response be aroused, but they do not infallibly arouse it even if they are contiguous.

The law of contiguity is incomplete, also, because it is not applicable to the association of two motor acts into a cooerdinated higher unit, or of the combination of two primary emotions into a higher emotional unit.

In a word, the time-honored law of association is no longer satisfactory because it does not fit into a stimulus-response psychology. It comes down from a time when the motor side of mental performances was largely overlooked by psychology, and when the individual was pictured as being passively "impressed" with the combinations of facts that were presented to his senses.

The Law of Combination

What we need, then, as an improvement on the old law of association by contiguity, and as a supplement to the law of exercise, is some law governing the response to two or more contiguous stimuli. Now we already have such a law, which we put to some use in studying attention, [Footnote: See pp. 268-264.] and called the law of "combination", or of "unitary response to a plurality of stimuli". We had better fetch that law out again and put it in good repair, and see whether it is adequate for the job that we now have on hand. In a very general, abstract form, the law of combination read that "two or more stimuli may arouse a single joint response". Let us add a single word, which had not risen above the horizon when we formulated the law before, and say that {399} two or more contiguous stimuli may arouse a single joint response.

That seems very little to say; can we possibly go far with so simple a statement? Well, let us see. In saying that two or more stimuli arouse a single response, we imply that there is already some rudimentary linkage between each stimulus and their common response, and that this linkage is used in arousing the response. Now bring in our trusty law of exercise, and we see that the use, or exercise, of such a linkage may strengthen it to such an extent that, later, a single one of the stimuli may arouse the response which was originally aroused by the whole collection of stimuli.

Does that promise any better? Probably it requires further discussion and exemplification before its value can be appreciated. Let us, then, first discuss it a bit, and then apply it to the explanation of the chief varieties of learned reaction that have come to our attention.

The law of combination attempts to show how it comes about that a stimulus, originally unable to arouse a certain response, acquires the power of arousing it; and the law states that this occurs only when the originally ineffective stimulus is combined with others which can and do arouse the response. The ineffective stimulus, being one of a combination of stimuli which collectively arouse the response, participates to some slight degree in arousing that response and may thus become effectively linked with the response.

Notice an assumption underlying the law of combination. Evidently a stimulus could not take part in arousing a response unless there were some pre-existing linkage between it and the response. This linkage may however be extremely loose and feeble, and wholly incapable by itself of arousing the response. The assumption of pre-existing loose linkage between almost any stimulus and almost any response is justified by the facts of playful behavior and trial and error {400} behavior. In addition to the close reflex connections provided in the native constitution, and in addition also to the close connections formed in previous training, there are at any time, and especially in childhood and youth, a vast number of loose connections. These are too weak to operate singly, until they have cooeperated in producing a response, and thus been individually strengthened, after which they may be able singly to produce the response.

The law of combination, then, as applied to learning, includes four points:

(a) A collection of stimuli may work together and arouse a single response.

(b) This is possible because of pre-existing loose linkage between the separate stimuli and the response.

(c) When any stimulus, working together with others, helps to arouse a response, its linkage with that response is strengthened by exercise.

(d) The linkage may be sufficiently strengthened so that a single stimulus can arouse the response without help from the other stimuli that were originally necessary.

Having now abundantly stated and reiterated the law of combination in the abstract, let us turn to concrete instances of learned reactions, and see how the law takes care of them. We have already classified a large share of all the concrete instances under a few main heads, as substitute stimulus, substitute response, combination (or association) of stimuli, and combination of responses. We shall presently find it possible to reduce these four classes to two, since the association of two objects, by virtue of which one of them later recalls the other, is a rather complicated case of substitute stimulus, while the combination of movements into a higher unit is a complicated case of substitute response.

[Footnote: To distinguish between "substitute stimulus" and "substitute response" is, in strict logic, like distinguishing between "inside out" and "outside in." Whenever there is a substitute stimulus there is also a substitute response, of course, since this stimulus, in being substituted for another, gets that other's response in place of its own original response; and in the same way, you can always find substitute stimulus in any instance of substitute response; for, in being substituted for another, a response gets that other's stimulus in place of its own original stimulus. For all that, the distinction between the two main cases of learning is of some importance, since sometimes the changed stimulus, and sometimes the changed response, is the interesting fact.]

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I. SUBSTITUTE STIMULUS EXPLAINED BY THE LAW OF COMBINATION

Here the response, without being itself essentially changed, becomes attached to a new stimulus. We distinguish two cases under the general head of substitute stimulus. In the one case, the substitute stimulus was originally extraneous, and unnecessary for arousing the response, while in the other case it was originally necessary as part of a team of stimuli that aroused the response.

A. Substitute Stimulus Originally Unnecessary for Arousing the Response

1. Conditioned reflex.

This is the very simplest case belonging under the law of combination. The dog that responded to the bell by a flow of saliva, after the bell plus a tasting substance had acted together on him time after time, is the typical instance; and another good instance is that of the little child who was "taught" to shrink from a rabbit by the sounding of a harsh noise along with the showing of the rabbit. [Footnote: See p. 303.] The explanation of all instances of conditioned reflex is the same. We have an effective stimulus acting, i.e., a stimulus strongly linked with the response; and we also have acting an ineffective stimulus, which gets drawn into the same reaction. The effective stimulus determines what response shall be made, and the other stimulus finds an outlet {402} into that response, being, as it seems, attracted towards the activated response, sucked into it. The weak linkage from the ineffective stimulus to the response, being thus used and strengthened, later enables this stimulus to arouse the response single-handed.

This sort of thing is best presented in a diagram. A full line in the diagram denotes a linkage strong enough to work alone, while a dotted line denotes a weak linkage. Letters stand for stimuli and responses. In the diagram for conditioned reflex, A is the original effective stimulus (the rasping noise in the instance of the child and the rabbit), and B is the ineffective stimulus (the sight of the rabbit). R is the shrinking response, linked strongly to the stimulus A and only weakly to the stimulus B, which has several other linkages fully as good as the linkage B-R. But A arouses the response R; and R, being thus activated, draws on B and brings the linkage B-R into use. After this has occurred a number of times, the linkage B-R has been so strengthened by repeated exercise that it can operate alone, so that the rabbit brings the shrinking response even in the absence of A, the noise.



At first, the child shrinks from the noise, but, the rabbit being before his eyes, he incidentally shrinks from the rabbit as well. He really shrinks in response to all the stimuli acting on him at that moment. He shrinks from the whole situation. He makes a unitary response to the whole collection of contiguous stimuli, and thus exercises the linkage between each stimulus and their joint response. The {403} linkage between rabbit and shrinking is later strong enough to work alone. It is a clear case of the law of combination.

2. Learning the names of things.

A child who can imitate simple words that he hears is shown a penny and the word "penny" is spoken to him. To this combination of stimuli he responds by saying the word. This is primarily a response to the auditory stimulus, since the sight of the penny, though it might probably have aroused some response, and even some vocal response from the child, had no strong linkage with this particular vocal response. But the auditory stimulus determined the response, and attracted the visual stimulus into this particular channel of saying "penny". The linkage from the sight of the penny to the saying of this word being thus strengthened by exercise, the seen penny later gives the right vocal response, without any auditory stimulus to assist.



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B. Substitute Stimulus Originally an Essential Member Of A Team of Stimuli That Aroused the Response

1. Observed grouping or relationship.

"Learning by observation" is a very important human accomplishment, and we found many evidences of its importance in our study of the process of memorizing. The facts observed, which assist memory so greatly, are usually relations or groups.



Evidently the observation of a group of things is a response to a collection of stimuli, and could not originally be aroused by any one of the stimuli alone. The same is true of observing a relationship; the observation is a response to two things taken together, and not, originally, to either of the two things taken alone. In spite of this, a single one of the things may later call to mind the relationship, or the group; that is, it arouses the response originally made to the pair or group of stimuli. The single stimulus has been substituted for the team that originally aroused the response. Its linkage with the response has been so strengthened by exercise as to operate effectively without assistance.

For example, in learning pairs of words in a "paired {405} associates experiment", [Footnote: See p. 336.] the subject is apt to find some relation between the words forming a pair, even though they are supposed to be "unrelated words". When he has thus learned the pair, either of the words in it will recall the observed relation and the other word of the pair. Sometimes, after a long interval especially, the relation is recalled without the other word. One subject fixed the pair, "windy—occupy", by thinking of a sailor occupying a windy perch up in the ropes. Some weeks later, on being given the word "windy", he recalled the sailor on the perch, but could not get the word "occupy". That is, he made the same response to "windy" that he had originally made to "windy—occupy", but did not get the response completely enough to give the second word.

In the typical cases of association by contiguity when one object reminds us of another that was formerly experienced together with it, the law of combination comes in as just described. The two objects were observed to be grouped or related in some way, or some such unitary response was made to the two objects taken together, and this response became so linked to each of the objects that later a single one of them arouses this unitary response and recalls the other object. In the free association test, [Footnote: See p. 380.] the stimulus word "dimple" calls up the previously made response of seeing a dimple in a cheek, and so leads to the word "cheek". In a controlled association test, where opposites are required, the stimulus word "mythical" arouses the previously made observation of the antithesis of mythical and historical, and so leads to the motor response of saying the latter word.

[Footnote: When, however, this indirect linkage between stimulus and motor response is frequently exercised, short-circuiting takes place (see p. 338), and the stimulus word arouses the motor response directly. Short-circuiting follows the law of combination very nicely. Let a stimulus S arouse an idea I and this in turn a motor act M. S—I—M represents the linkages used. But undoubtedly there is a weak pre-existing linkage directly across from S to M, and this gets used to a slight degree, strictly according to the conditioned reflex diagram, with I playing the part of the effective stimulus in arousing M, and S the part of the originally ineffective stimulus. By dint of being exercised in this way, the linkage S—M becomes strong enough to arouse the motor response directly, and I is then very likely to be left out altogether.]

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2. Response by analogy and association by similarity.

When an object reminds me of a similar object, that is association by similarity. But suppose I actually take the object to be the similar object, and behave towards it accordingly; then my reaction is called "response by analogy". Once, when far from home, I saw a man whom I took to be an acquaintance from my home town, and stepped up to him, extending my hand. He did not appear very enthusiastic, and informed me that, in his opinion, I had made a mistake. This was response by analogy, but if I had simply said to myself that that man looked like my acquaintance, that would have been association by similarity. Really, association by similarity is the more complex response, for it involves response to the points of newness in the present object, as well as to the points of resemblance to the familiar object, whereas response by analogy consists simply in responding to the points of resemblance.

Response by analogy often appears in little children, as when they call all men "papa"' or as when they call the squirrel a "kitty" when first seen. If they call it a "funny kitty", that is practically association by similarity, since the word "funny" is a response to the points in which a squirrel is different from a cat, while the word "kitty" is a response to the points of resemblance.

But response by analogy is not always so childish or comic as the above examples might seem to imply. When we respond to a picture by recognizing the objects depicted, that is response by analogy, since the pictured object is only {407} partially like the real object; a bare outline drawing may be enough to arouse the response of "seeing" the object. Other instances of response by analogy will come to light when, in the next chapter, we come to the study of perception.



The machinery of response by analogy is easily understood by aid of the law of combination. A complex object, presenting a number of parts and characteristics, arouses the response of seeing and perhaps naming the object. This is a unitary response to a collection of stimuli, and each of the parts or characteristics of the object participates in arousing the response, and the linkage of each part with the response is thus strengthened. Later, therefore, the whole identical object is not required to arouse this same {408} response, but some of its parts or characteristics will give the response, and they may do this even when they are present in an object that has other and unfamiliar parts and characteristics.

The machinery of association by similarity is the same, with the addition of a second response, called out by the new characteristics of the present object.

II. SUBSTITUTE RESPONSE EXPLAINED BY THE LAW OF COMBINATION

The substitute response machinery is more complicated than that of the substitute stimulus, as it includes the latter and something more. What that something more is will be clear if we ask ourselves why a substitute response should ever be made. Evidently because there is something wrong with the original response; if that were entirely satisfactory, it would continue to be made, and there would be no room for a substitute. The original response being unsatisfactory to the individual, how is he to find a substitute? Only by finding some stimulus that will arouse it. This is where trial and error come in, consisting in a search for some extra stimulus that shall give a satisfactory response.

Suppose now that the extra stimulus has been found which arouses a satisfactory substitute response. The original stimulus, or the reaction-tendency aroused by it, still continuing, participates in arousing the substitute response, playing the part of the originally ineffective stimulus in the conditioned reflex. Thus the original stimulus becomes strongly linked with the substitute response.

The process of reaching a substitute response thus includes three stages: (a) original response found unsatisfactory, (b) new stimulus found which gives a satisfactory substitute response, (c) attachment of the substitute response to the original stimulus.

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There are two main cases under the general head of substitute response. In one case, the substitute response is essentially an old response, not acquired during the process of substitution, but simply substituted, as indicated just above, for the original response to the situation. This represents the common trial and error learning of animals. The second case is that where the substitute response has to be built up by combination of old responses into a higher unit.

C. Substitute Response, but not in Itself a New Response

I. Trial and error.

Our much-discussed instance of the cat in the cage need not be described again, but may simply be illustrated by a diagram.



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2. Learning to balance on a bicycle.

When the beginner feels the bicycle tipping to the left, he naturally responds by leaning to the right, and even by turning the wheel to the right. Result unsatisfactory—strained position and further tipping to the left. As the bicyclist is about to fall, he saves himself by a response which he has previously learned in balancing on his feet; he extends his foot to the left, which amounts to a response to the ground on the left as a good base of support. Now let him sometime respond to the ground on his left by turning his wheel that way, and, to his surprise and gratification, he finds the tipping overcome, and his balance well maintained. The response of turning to the left, originally made to the ground on the left (but in part to the tipping), becomes so linked with the tipping as to be the prompt reaction whenever tipping is felt. The diagram of this process would be the same as for the preceding instance.

D. Substitute Response, the Response Being a Higher Motor Unit

1. The brake and clutch combination in driving an automobile.

This may serve as an instance of simultaneous cooerdination, since the two movements which are combined into a higher unit are executed simultaneously. The beginner in driving an automobile often has considerable trouble in learning to release the "clutch", which, operated by the left foot, ungears the car from the engine, and so permits the car to be stopped without stopping the engine. The foot brake, operated by the right foot, is comparatively easy to master, because the necessity for stopping the car is a perfectly clear and definite stimulus. Now, when the beginner gets a brake-stimulus, he responds promptly with his right foot, but neglects to employ his left foot on the clutch, because he has no effective clutch-stimulus; there is nothing {411} in the situation that reminds him of the clutch. Result, engine stalled, ridicule for the driver. Next time, perhaps, he thinks "clutch" when he gets the brake-stimulus, and this thought, being itself a clutch-stimulus, arouses the clutch-response simultaneously with the brake-response. After doing this a number of times, the driver no longer needs the thought of the clutch as a stimulus, for the left foot movement on the clutch has become effectively linked with the brake-stimulus, so that any occasion that arouses the brake-response simultaneously arouses the clutch response.



The combination of two responses is effected by linking both to the same stimulus; thus the two become united into a cooerdinated higher motor unit.

2. The word-habit in typewriting furnishes an example of successive cooerdination, the uniting of a sequence of movements into a higher unit. [Footnote: See p. 324.] The beginner has to spell out {412} the word he is writing, and make a separate response to each letter; but when he has well mastered the letter-habits, and, still unsatisfied, is trying for more speed, it happens that he thinks ahead while writing the first letter of a word, and prepares for the second letter. In effect, he commences reacting to the second letter while still writing the first. This goes further, till he anticipates the series of letters forming a short word while still at the beginning of the word. The letter movements are thus linked to the thought of the word as a whole, and the word becomes an effective stimulus for arousing the series of letter movements.



Many other instances of learning can be worked out in the same way, and there seems to be no difficulty in {413} interpreting any of them by the law of combination. Even "negative adaptation" can possibly be interpreted as an instance of substitute response; some slight and easy response may be substituted for the avoiding reaction or the attentive reaction that an unimportant stimulus at first arouses, these reactions being rather a nuisance when they are unnecessary. On the whole, the law of combination seems to fill the bill very well. It explains what the law of exercise left unexplained. It always brings in the law of exercise as an ally, and, in explaining substitute response, it brings in the law of effect, which however, as we saw before, may be a sub-law under the law of exercise. These two, or three laws, taken together, give an adequate analysis of the whole process of learning.

The Law of Combination in Recall

Unitary response to multiple stimuli is important in recall as well as in learning. The clearest case of this is afforded by "controlled association". [Footnote: See p. 381.]

In an opposites test, the response to the stimulus word "long" is aroused partly by this stimulus word, and partly by the "mental set" for opposites. There are two lines of influence, converging upon the response, "long—short" (of which only the word "short" may be spoken): one line from the stimulus word "long", and the other from the mental set for pairs of opposite words. The mental set for opposites tends to arouse any pair of opposites; the word "long" tends to arouse any previously observed group of words of which "long" is a part. The mental set, an internal stimulus, and the stimulus word coming from outside, converge or combine to arouse one particular response.

The mental set for adding has previously exercised {414} linkages with the responses composing the addition table, while the mental set for multiplication has linkages with the responses composing the multiplication table. When the set for adding is active, a pair of numbers, seen or heard, together with this internal stimulus of the mental set, arouses the response that gives the sum; but when the multiplying set is active, the same pair of numbers gives the product as the response. All thinking towards any goal is a similar instance of the law of combination.

The Laws of Learning in Terms of the Neurone

We have good evidence that the brain is concerned in learning and retention. Loss of some of the cortex through injury often brings loss of learned reactions, and the kind of reactions lost differs with the part of the cortex affected. Injury in the occipital lobe brings loss of visual knowledge, and injury in the neighborhood of the auditory sense-center brings loss of auditory knowledge.

Injury to the retina or optic nerve, occurring early in life, results in an under-development of the cortex in the occipital lobe. The nerve cells remain small and their dendrites few and meager, because they have not received their normal amount of exercise through stimulation from the eye.

Exercise, then, has the same general effect on neurones that it has on muscles; it causes them to grow and it probably also improves their internal condition so that they act more readily and more strongly. The growth, in the cortex, of dendrites and of the end-brushes of axons that interlace with the dendrites, must improve the synapses between one neurone and another, and thus make better conduction paths between one part of the cortex and another, and also between the cortex and the lower sensory and motor centers.

The law of exercise has thus a very definite meaning when {415} translated into neural terms. It means that the synapses between stimulus and response are so improved, when traversed by nerve currents in the making of a reaction, that nerve currents can get across them more easily the next time.



The more a synapse is used, the better synapse it becomes, and the better linkage it provides between some stimulus and some response. The cortex is the place where linkages are made in the process of learning, and it is there also that forgetting, or atrophy, takes place through disuse. Exercise makes a synapse closer, disuse lets it relapse into a loose and poorly conducting state.

The law of combination, also, is readily translated into {416} neural terms. The "pre-existing loose linkages" which it assumed to exist undoubtedly do exist in the form of "association fibers" extending in vast numbers from any one part of the cortex to many other parts. These fibers are provided by native constitution, but probably terminate rather loosely in the cortex until exercise has developed them. They may be compared to telephone wires laid down in the cables through the streets and extending into the houses, but still requiring a little fine work to attach them properly to the telephone instruments.

[Illustration: Fig. 64.—Diagram for the learning of the name of an object, transformed into a neural diagram. The vocal movement of saying the name is made in response to the auditory stimulus of hearing the name, but when the neurone in the "speech center" is thus made active, it takes up current also from the axon that reaches it from the visual center, even though the synapse between this axon and the speech neurone is far from close. This particular synapse between the visual and the speech centers, being thus exercised, is left in an improved condition. Each neurone in the diagram represents hundreds in the brain, for brain activities are carried on by companies and regiments of neurones. (Figure text: object seen, visual center name heard, auditory center, speech center, name spoken)]

The diagrams illustrating different cases under the law of combination can easily be perfected into neural diagrams, though, to be sure, any diagram is ultra-simple as compared with the great number of neurones that take part in even a simple reaction.

The reader will be curious to know now much of this neural interpretation of our psychological laws is observed fact, and how much speculation. Well, we cannot as yet {417} observe the brain mechanism in actual operation—not in any detail. We have good evidence, as already outlined, for growth of the neurones and their branches through exercise.



We have perfectly good evidence of the law of "unitary response to multiple stimuli" from the physiological study of reflex action; and we have perfectly good anatomical evidence of the convergence and divergence of neural paths of connection, as required by the law of combination. The association fibers extending from one part to another of the cortex are an anatomical fact. [Footnote: See p. 56.] Facilitation is a fact, and that means that a stimulus which could not of itself arouse a response can cooeperate with another stimulus that has a direct connection with that response, and reinforce its effect. In short, all the elements required for a neural law of combination are known facts, and the only matter of doubt is whether we have built these elements together aright in our interpretation. It is not pure speculation, by any means.

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EXERCISES

1. Outline the chapter, in the form of a list of laws and sub-laws.

2. Review the instances of learning cited in Chapters XIII-XV, and examine whether they are covered and sufficiently accounted for by the general laws given in the present chapter.

3. Draw diagrams, like those given in this chapter, for the simpler cases, at least, that you have considered in question 2.

4. Show that response by analogy is important in the development of language. Consider metaphor, for example, and slang, and the using of an old word in a new sense (as in the case of 'rail-road').

REFERENCES

William James devoted much thought to the problem of the mechanism of learning, habit, association, etc., and his conclusions are set forth in several passages in his Principles of Psychology, 1890, Vol. I, pp. 104-112, 554-594, and Vol. II, pp. 578-592.

Another serious consideration of the matter is given by William McDougall in his Physiological Psychology, 1905, Chapters VII and VIII.

See also Thorndike's Educational Psychology, Briefer Course, 1914, Chapter VI.

On the whole subject of association, see Howard C. Warren, A History of the Association Psychology, 1921.

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CHAPTER XVII

PERCEPTION

MENTAL LIFE CONSISTS LARGELY IN THE DISCOVERY OF FACTS NEW TO THE INDIVIDUAL, AND IN THE RE-DISCOVERY OF FACTS PREVIOUSLY OBSERVED

You will remember the case of John Doe, who was brought before us for judgment on his behavior, as to how far it was native and how far acquired. We have since that time been occupied in hearing evidence on the case, and after mature consideration have reached a decision which we may formulate as follows: that this man's behavior is primarily instinctive or native, but that new attachments of stimulus and response, and new combinations of responses, acquired in the process of learning, have furnished him with such an assortment of habits and skilled acts of all sorts that we can scarcely identify any longer the native reactions out of which his whole behavior is built. That decision being reached, we are still not ready to turn the prisoner loose, but wish to keep him under observation for a while longer, in order to see what use he makes of this vast stock of native and acquired reactions. We wish to know how an individual, so equipped, behaves from day to day, and meets the exigencies of life. Such, in brief, is the task we have still before us.

Accordingly, one fine morning we enter our prisoner's sleeping quarters, and find him, for once, making no use of his acquired reactions, as far as we can see, and utilizing but a small fraction of his native reactions. He is, in short, asleep. We ring a bell, and he stirs uneasily. We {420} ring again, and he opens his eyes sleepily upon the bell, then spies us and sits bolt upright in bed. "Well, what . . ." He throws into action a part of his rather colorful vocabulary. He evidently sees our intrusion in an unfavorable light at first, but soon relaxes a little and "supposes he must be late for breakfast". Seeing our stenographer taking down his remarks, he is puzzled for a moment, then breaks into a loud laugh, and cries out, "Oh! This is some more psychology. Well, go as far as you like. It must have been your bell I heard in my dream just now, when I thought I saw a lot of cannibals beating the tom-tom". Having now obtained sufficient data for quite a lengthy discussion, we retire to our staff room and deliberate upon these manifestations.

"The man perceives", we agree. "By the use of his eyes and ears he discovered facts, and interpreted them in the light of his previous experience. In knowing the facts, he also got adjusted to them and governed his actions by them. But notice—a curious thing—how his perception of the facts progressed by stages from the vague and erroneous to the correct and precise. Before he was fully awake, he mistook the bell for a tom-tom; then, more fully aroused, he knew the bell. Ourselves he first saw as mere wanton intruders, then as cheerful friends who wished him no ill; finally he saw us in our true character as investigators of his behavior."

Following our man through the day's work and recreation, we find a large share of his mental activity to consist in the perception of facts. We find that he makes use of the facts, adjusting himself to them and also shaping them to suit himself. His actions are governed by the facts perceived, at the same time that they are governed by his own desires. Ascertaining how the facts stand, he takes a hand and manipulates them. He is constantly coming to know {421} fresh facts, and constantly doing something new with them. His life is a voyage of discovery, and at the same time a career of invention.

Discovery and invention!—high-sounding words, still they are applicable to everyday life. The facts observed may not be absolutely new, but at least they have always to be verified afresh, since action needs always to take account of present reality. The invention may be very limited in scope, but seldom does an hour pass that does not call for doing something a little out of the ordinary, so as to escape from a fresh trap or pluck fruit from a newly discovered bough. All of our remaining chapters might, with a little forcing, be pigeonholed under these two great heads. Discovery takes its start with the child's instinctive exploratory activity, and invention with his manipulation, and these two tendencies, perhaps at bottom one, remain closely interlinked throughout.

Some Definitions

Perception is the culmination of the process of discovery. Discovery usually requires exploration, a search for facts; and it requires attention, which amounts to finding the facts or getting them effectively presented; and perception then consists in knowing the presented facts.

When the facts are presented to the senses, we speak of "sense perception". If they are presented to the eye, we speak of visual perception; if to the ear, of auditory perception, etc. But when we speak of a fact as being "presented" to the eye or ear, we do not necessarily mean that it is directly and completely presented; it may only be indicated. We may have before the eyes simply a sign of some fact, but perceive the fact which is the meaning of the sign. We look out of the window and "see it is wet to-day", though wetness is something to be felt rather than seen; {422} having previously observed how wet ground looks, we now respond promptly to the visual appearance by knowing the indicated state of affairs. In the same way, we say that we "hear the street car", though a street car, we must admit, is not essentially a noise. What we hear, in strictness, is a noise, but we respond to the noise by perceiving the presence of the car. Responding to a stimulus presented to one sense by perceiving a fact which could only be directly presented to another sense is exemplified also by such common expressions as that the stone "looks heavy", or that the bell "sounds cracked". or that the jar of fruit "smells sour". Sense perception, then, is responding to a stimulus by knowing some fact indicated by it either directly or indirectly. Perception that is not sense perception occurs when the fact perceived is not even indirectly presented to the senses at the moment. The fact is then presented by recall; yet the fact in question is not recalled. Recall not only gives you facts previously perceived, but may provide the data, the stimulus, for fresh perception. Putting together two recalled facts, you may perceive a further fact not previously known. Remembering that you took your umbrella to the office this morning in the rain, that it was fine when you left the office, and that you certainly did not have the umbrella when you reached home, you perceive that you must have left it at the office. Reading in the paper of preparations for another polar expedition, and remembering that both poles have already been discovered, you perceive that there is something more in polar exploration than the mere race for the pole. Perception of this sort amounts to "reasoning", and will be fully considered in another chapter, while here we shall focus our attention on sense perception.

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The Difference Between Perception and Sensation

If sense perception is a response to a sensory stimulus, so is sensation, and the question arises whether there is any genuine difference between these two. In the instance of "hearing the street car", the difference is fairly obvious; hearing the noise is sensation, while knowing the street car to be there is perception.

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