Whence came the thought that occupies you this moment, and what determines the next that is to follow? Introspection reveals no more interesting fact concerning our minds than that our thoughts move in a connected and orderly array and not in a hit-and-miss fashion. Our mental states do not throng the stream of consciousness like so many pieces of wood following each other at random down a rushing current, now this one ahead, now that. On the contrary, our thoughts come, one after the other, as they are beckoned or caused. The thought now in the focal point of your consciousness appeared because it sprouted out of the one just preceding it; and the present thought, before it departs, will determine its successor and lead it upon the scene. This is to say that our thought stream possesses not only a continuity, but also a unity; it has coherence and system. This coherence and system, which operates in accordance with definite laws, is brought about by what the psychologist calls association.

1. THE NATURE OF ASSOCIATION

We may define association, then, as the tendency among our thoughts to form such a system of bonds with each other that the objects of consciousness are vitally connected both (1) as they exist at any given moment, and (2) as they occur in succession in the mental stream.

The Neural Basis of Association.—The association of thoughts—ideas, images, memory—or of a situation with its response, rests primarily on a neural basis. Association is the result of habit working in neurone groups. Its fundamental law is stated by James as follows: "When two elementary brain-processes have been active together or in immediate succession, one of them, on recurring, tends to propagate its excitement into the other." This is but a technical statement of the simple fact that nerve currents flow most easily over the neurone connections that they have already used.

It is hard to teach an old dog new tricks, because the old tricks employ familiar, much-used neural paths, while new tricks require the connecting up of groups of neurones not in the habit of working together; and the flow of nerve energy is more easily accomplished in the neurones accustomed to working together. One who learns to speak a foreign language late in life never attains the facility and ease that might have been reached at an earlier age. This is because the neural paths for speech are already set for his mother-tongue, and, with the lessened plasticity of age, the new paths are hard to establish.

The connections between the various brain areas, or groups of neurones, are, as we have seen in an earlier chapter, accomplished by means of association fibers. This function requires millions of neurones, which unite every part of the cortex with every other part, thus making it possible for a neural activity going on in any particular center to extend to any other center whatsoever. In the relatively unripe brain of the child, the association fibers have not yet set up most of their connections. The age at which memory begins is determined chiefly by the development of a sufficient number of association fibers to bring about recall. The more complex reasoning, which requires many different associative connections, is impossible prior to the existence of adequate neural development. It is this fact that makes it futile to attempt to teach young children the more complicated processes of arithmetic, grammar, or other subjects. They are not yet equipped with the requisite brain machinery to grasp the necessary associations.

Association the Basis of Memory.—Without the machinery and processes of association we could have no memory. Let us see in a simple illustration how association works in recall. Suppose you are passing an orchard and see a tree loaded with tempting apples. You hesitate, then climb the fence, pick an apple and eat it, hearing the owner's dog bark as you leave the place. The accompanying diagram will illustrate roughly the centers of the cortex which were involved in the act, and the association fibers which connect them. (See Fig. 18.) Now let us see how you may afterward remember the circumstance through association. Let us suppose that a week later you are seated at your dining table, and that you begin to eat an apple whose flavor reminds you of the one which you plucked from the tree. From this start how may the entire circumstance be recalled? Remember that the cortical centers connected with the sight of the apple tree, with our thoughts about it, with our movements in getting the apple, and with hearing the dog bark, were all active together with the taste center, and hence tend to be thrown into activity again from its activity. It is easy to see that we may (1) get a visual image of the apple tree and its fruit from a current over the gustatory-visual association fibers; (2) the thoughts, emotions, or deliberations which we had on the former occasion may again recur to us from a current over the gustatory-thought neurones; (3) we may get an image of our movements in climbing the fence and picking the apple from a current over the gustatory-motor fibers; or (4) we may get an auditory image of the barking of the dog from a current over the gustatory-auditory fibers. Indeed, we are sure to get some one or more of these unless the paths are blocked in some way, or our attention leads off in some other direction.

Factors Determining Direction of Recall.—Which of these we get first, which of the images the taste percept calls to take its place as it drops out of consciousness, will depend, other things being equal, on which center was most keenly active in the original situation, and is at the moment most permeable. If, at the time we were eating the stolen fruit, our thoughts were keenly self-accusing for taking the apples without permission, then the current will probably discharge through the path gustatory-thought, and we shall recall these thoughts and their accompanying feelings. But if it chances that the barking of the dog frightened us badly, then more likely the discharge from the taste center will be along the path gustatory-auditory, and we shall get the auditory image of the dog's barking, which in turn may call up a visual image of his savage appearance over the auditory-visual fibers. It is clear, however, that, given any one of the elements of the entire situation back, the rest are potentially possible to us, and any one may serve as a "cue" to call up all the rest. Whether, given the starting point, we get them all, depends solely on whether the paths are sufficiently open between them for the current to discharge between them, granting that the first experience made sufficient impression to be retained.

Since this simple illustration may be made infinitely complex by means of the millions of fibers which connect every center in the cortex with every other center, and since, in passing from one experience to another in the round of our daily activities, these various areas are all involved in an endless chain of activities so intimately related that each one can finally lead to all the others, we have here the machinery both of retention and of recall—the mechanism by which our past may be made to serve the present through being reproduced in the form of memory images or ideas. Through this machinery we are unable to escape our past, whether it be good or bad; for both the good and the bad alike are brought back to us through its operations.

When the repetition of a series of acts has rendered habit secure, the association is relatively certain. If I recite to you A-B-C-D, your thought at once runs on to E, F, G. If I repeat, "Tell me not in mournful numbers," association leads you to follow with "Life is but an empty dream." Your neurone groups are accustomed to act in this way, so the sequence follows. Memorizing anything from the multiplication table to the most beautiful gems of poetic fervor consists, therefore, in the setting up of the right associative connections in the brain.

Association in Thinking.—All thinking proceeds by the discovery or recognition of relations between the terms or objects of our thought. The science of mathematics rests on the relations found to exist between numbers and quantities. The principles and laws of natural science are based on the relations established among the different forms of matter and the energy that operates in this field. So also in the realm of history, art, ethics, or any other field of human experience. Each fact or event must be linked to other facts or events before it possesses significance. Association therefore lies at the foundation of all thinking, whether that of the original thinker who is creating our sciences, planning and executing the events of history, evolving a system of ethics, or whether one is only learning these fields as they already exist by means of study. Other things being equal, he is the best thinker who has his knowledge related part to part so that the whole forms a unified and usable system.

Association and Action.—Association plays an equally important part in all our motor responses, the acts by which we carry on our daily lives, do our work and our play, or whatever else may be necessary in meeting and adapting ourselves to our environment. Some sensations are often repeated, and demand practically the same response each time. In such cases the associations soon become fixed, and the response certain and automatic. For example, we sit at the table, and the response of eating follows, with all its complex acts, as a matter of course. We lie down in bed, and the response of sleep comes. We take our place at the piano, and our fingers produce the accustomed music.

It is of course obvious that the influence of association extends to moral action as well. In general, our conduct follows the trend of established associations. We are likely to do in great moral crises about as we are in the habit of doing in small ones.

2. THE TYPES OF ASSOCIATION

Fundamental Law of Association.—Stated on the physiological side, the law of habit as set forth in the definition of association in the preceding section includes all the laws of association. In different phrasing we may say: (1) Neurone groups accustomed to acting together have the tendency to work in unison. (2) The more frequently such groups act together the stronger will be the tendency for one to throw the other into action. Also, (3) the more intense the excitement or tension under which they act together the stronger will be the tendency for activity in one to bring about activity in the other.

The corresponding facts may be expressed in psychological terms as follows: (1) Facts accustomed to being associated together in the mind have a tendency to reappear together. (2) The more frequently these facts appear together the stronger the tendency for the presence of one to insure the presence of the other. (3) The greater the tension, excitement or concentration when these facts appear in conjunction with each other, the more certain the presence of one is to cause the presence of the other.

Several different types of association have been differentiated by psychologists from Aristotle down. It is to be kept in mind, however, that all association types go back to the elementary law of habit-connections among the neurones for their explanation.

Association by Contiguity.—The recurrence in our minds of many of the elements from our past experience is due to the fact that at some time, possibly at many times, the recurring facts were contiguous in consciousness with some other element or fact which happens now to be again present. All have had the experience of meeting some person whom we had not seen for several months or years, and having a whole series of supposedly forgotten incidents or events connected with our former associations flood into the mind. Things we did, topics we discussed, trips we took, games we played, now recur at the renewal of our acquaintance. For these are the things that were contiguous in our consciousness with our sense of the personality and appearance of our friend. And who has not in similar fashion had a whiff of perfume or the strains of a song recall to him his childhood days! Contiguity is again the explanation.

At the Mercy of Our Associations.—Through the law thus operating we are in a sense at the mercy of our associations, which may be bad as well as good. We may form certain lines of interest to guide our thought, and attention may in some degree direct it, but one's mental make-up is, after all, largely dependent on the character of his associations. Evil thoughts, evil memories, evil imaginations—these all come about through the association of unworthy or impure images along with the good in our stream of thought. We may try to forget the base deed and banish it forever from our thinking, but lo! in an unguarded moment the nerve current shoots into the old path, and the impure thought flashes into the mind, unsought and unwelcomed. Every young man who thinks he must indulge in a little sowing of wild oats before he settles down to a correct life, and so deals in unworthy thoughts and deeds, is putting a mortgage on his future; for he will find the inexorable machinery of his nervous system grinding the hated images of such things back into his mind as surely as the mill returns to the sack of the miller what he feeds into the hopper. He may refuse to harbor these thoughts, but he can no more hinder their seeking admission to his mind than he can prevent the tramp from knocking at his door. He may drive such images from his mind the moment they are discovered, and indeed is guilty if he does not; but not taking offense at this rebuff, the unwelcome thought again seeks admission.

The only protection against the return of the undesirable associations is to choose lines of thought as little related to them as possible. But even then, do the best we may, an occasional "connection" will be set up, we know not how, and the unwelcome image stands staring us in the face, as the corpse of Eugene Aram's victim confronted him at every turn, though he thought it safely buried. A minister of my acquaintance tells me that in the holiest moments of his most exalted thought, images rise in his mind which he loathes, and from which he recoils in horror. Not only does he drive them away at once, but he seeks to lock and bar the door against them by firmly resolving that he will never think of them again. But alas! that is beyond his control. The tares have been sown among the wheat, and will persist along with it until the end. In his boyhood these images were given into the keeping of his brain cells, and they are only being faithful to their trust.

Association by Similarity and Contrast.—All are familiar with the fact that like tends to suggest like. One friend reminds us of another friend when he manifests similar traits of character, shows the same tricks of manner, or has the same peculiarities of speech or gesture. The telling of a ghost or burglar story in a company will at once suggest a similar story to every person of the group, and before we know it the conversation has settled down to ghosts or burglars. One boastful boy is enough to start the gang to recounting their real or imaginary exploits. Good and beautiful thoughts tend to call up other good and beautiful thoughts, while evil thoughts are likely to produce after their own kind; like produces like.

Another form of relationship is, however, quite as common as similars in our thinking. In certain directions we naturally think in opposites. Black suggests white, good suggests bad, fat suggests lean, wealth suggests poverty, happiness suggests sorrow, and so on.

The tendency of our thought thus to group in similars and opposites is clear when we go back to the fundamental law of association. The fact is that we more frequently assemble our thoughts in these ways than in haphazard relations. We habitually group similars together, or compare opposites in our thinking; hence these are the terms between which associative bonds are formed.

Partial, or Selective, Association.—The past is never wholly reinstated in present consciousness. Many elements, because they had formed fewer associations, or because they find some obstacle to recall, are permanently dropped out and forgotten. In other words, association is always selective, favoring now this item of experience, now that, above the rest.

It is well that this is so; for to be unable to escape from the great mass of minutiÆ and unimportant detail in one's past would be intolerable, and would so cumber the mind with useless rubbish as to destroy its usefulness. We have surely all had some experience with the type of persons whose associations are so complete and impartial that all their conversation teems with unessential and irrelevant details. They cannot recount the simplest incident in its essential points but, slaves to literalness, make themselves insufferable bores by entering upon every lane and by-path of circumstance that leads nowhere and matters not the least in their story. Dickens, Thackeray, George Eliot, Shakespeare, and many other writers have seized upon such characters and made use of them for their comic effect. James, in illustrating this mental type, has quoted the following from Miss Austen's "Emma":

"'But where could you hear it?' cried Miss Bates. 'Where could you possibly hear it, Mr. Knightley? For it is not five minutes since I received Mrs. Cole's note—no, it cannot be more than five—or at least ten—for I had got my bonnet and spencer on, just ready to come out—I was only gone down to speak to Patty again about the pork—Jane was standing in the passage—were not you, Jane?—for my mother was so afraid that we had not any salting-pan large enough. So I said I would go down and see, and Jane said: "Shall I go down instead? for I think you have a little cold, and Patty has been washing the kitchen." "Oh, my dear," said I—well, and just then came the note.'"

The Remedy.—The remedy for such wearisome and fruitless methods of association is, as a matter of theory, simple and easy. It is to emphasize, intensify, and dwell upon the significant and essential in our thinking. The person who listens to a story, who studies a lesson, or who is a participant in any event must apply a sense of value, recognizing and fixing the important and relegating the trivial and unimportant to their proper level. Not to train one's self to think in this discriminating way is much like learning to play a piano by striking each key with equal force!

3. TRAINING IN ASSOCIATION

Since association is at bottom nothing but habit at work in the mental processes, it follows that it, like other forms of habit, can be encouraged or suppressed by training. Certainly, no part of one's education is of greater importance than the character of his associations. For upon these will largely depend not alone the content of his mental stream, the stuff of his thinking, but also its organization, or the use made of the thought material at hand. In fact, the whole science of education rests on the laws and principles involved in setting up right systems of associative connections in the individual.

The Pleasure-Pain Motive in Association.—A general law seems to obtain throughout the animal world that associative responses accompanied by pleasure tend to persist and grow stronger, while those accompanied by pain tend to weaken and fall away. The little child of two years may not understand the gravity of the offense in tearing the leaves out of books, but if its hands are sharply spatted whenever they tear a book, the association between the sight of books and tearing them will soon cease. In fact, all punishment should have for its object the use of pain in the breaking of associative bonds between certain situations and wrong responses to them.

On the other hand, the dog that is being trained to perform his tricks is rewarded with a tidbit or a pat when the right response has been made. In this way the bond for this particular act is strengthened through the use of pleasure. All matter studied and learned under the stimulus of good feeling, enthusiasm, or a pleasurable sense of victory and achievement not only tends to set up more permanent and valuable associations than if learned under opposite conditions, but it also exerts a stronger appeal to our interest and appreciation.

The influence of mental attitude on the matter we study raises a question as to the wisdom of assigning the committing of poetry, or Bible verses, or the reading of so many pages of a literary masterpiece as a punishment for some offense. How many of us have carried away associations of dislike and bitterness toward some gem of verse or prose or Scripture because of having our learning of it linked up with the thought of an imposed task set as penance for wrong-doing! One person tells me that to this day she hates the sight of Tennyson because this was the volume from which she was assigned many pages to commit in atonement for her youthful delinquencies.

Interest as a Basis for Association.—Associations established under the stimulus of strong interest are relatively broad and permanent, while those formed with interest flagging are more narrow and of doubtful permanence. This statement is, of course, but a particular application of the law of attention. Interest brings the whole self into action. Under its urging the mind is active and alert. The new facts learned are completely registered, and are assimilated to other facts to which they are related. Many associative connections are formed, hence the new matter is more certain of recall, and possesses more significance and meaning.

Association and Methods of Learning.—The number and quality of our associations depends in no small degree on our methods of learning. We may be satisfied merely to impress what we learn on our memory, committing it uncritically as so many facts to be stored away as a part of our education. We may go a step beyond this and grasp the simplest and most obvious meanings, but not seek for the deeper and more fundamental relations. We may learn separate sections or divisions of a subject, accepting each as a more or less complete unit, without connecting these sections and divisions into a logical whole.

But all such methods are a mistake. They do not provide for the associative bonds between the various facts or groups of facts in our knowledge, without which our facts are in danger of becoming but so much lumber in the mind. Meanings, relations, definitely recognized associations, should attach to all that we learn. Better far a smaller amount of usable knowledge than any quantity of unorganized and undigested information, even if the latter sometimes allows us to pass examinations and receive honor grades. In short, real mastery demands that we think, that is relate and associate, instead of merely absorbing as we learn.

4. PROBLEMS IN OBSERVATION AND INTROSPECTION

1. Test the uncontrolled associations of a group of pupils by pronouncing to the class some word, as blue, and having the members write down 20 words in succession as rapidly as they can, taking in each instance the first word that occurs to them. The difference in the scope, or range, of associations, can easily be studied by applying this test to, say, a fourth grade and an eighth grade and then comparing results.

2. Have you ever been puzzled by the appearance in your mind of some fact or incident not thought of before for years? Were you able to trace out the associative connection that caused the fact to appear? Why are we sometimes unable to recall, when we need them, facts that we perfectly well know?

3. You have observed that it is possible to be able to spell certain words when they occur in a spelling lesson, but to miss them when employing them in composition. It is possible to learn a conjugation or a declension in tabular form, and then not be able to use the correct forms of words in speech or writing. Relate these facts to the laws of association, and recommend a method of instruction that will remove the discrepancy.

4. To test the quickness of association in a class of children, copy the following words clearly in a vertical column on a chart; have your class all ready at a given signal; then display the chart before them for sixty seconds, asking them to write down on paper the exact opposite of as many words as possible in one minute. Be sure that all know just what they are expected to do.

Bad, inside, slow, short, little, soft, black, dark, sad, true, dislike, poor, well, sorry, thick, full, peace, few, below, enemy.

Count the number of correct opposites got by each pupil.