perience may suffice as well as a repeated experience to produce long retention. But the fact is that a single vivid experience amounts to a repeated experience, because it is usually recalled so often in idea. If we could imagine a person's having a very forcible impression, which he did not once recall for a long period of years, it is doubtful whether he could recall it at the end of that time with anything like the success which attends his recollection of the familiar surroundings of his childhood.

CHAPTER XII

THE MEMORY IDEA

$92. Evidence for and against Ideas in Animals

In the last chapter we have seen that the behavior of the lower forms of animal life, at least, can be fully explained without supposing that the animals concerned ever consciously recall the effects of a previously experienced stimulus in the entire absence of the stimulus itself. We must admit that it is not easy to prove the possession by any animal of memory in the sense of having ideas of absent objects, rather than in the sense of behaving differently to present objects because of past experience with them. The dog shows clearly that he remembers his master in the latter sense by displaying joy at the sight of him. Can we be sure that he has remembered him in the former sense during his absence; that is, that he has had a memory image of him? Certain pieces of negative evidence have been noted. Where an animal learns to work a mechanism by gradually dropping off unnecessary movements, it looks as if its conduct were not guided by an idea of the right movements, for the association of ideas as we know it is so rapid a process that a single experience of two stimuli together is enough to enable one to revive the other in the form of a memory idea, provided that the experience was recent. When an animal has learned to run through a complicated labyrinth almost without error, but still persists in taking the wrong turning at the outset, we are surely justified in saying that if it has ideas, it does not use them as a human being would, for some kind of idea of the right way to start the laby

rinth course would certainly be formed in a human mind after a very few experiences. Thorndike's attempts to make cats and dogs learn by inferential imitation, and by putting them through the movements required, while they do not show absence of ideas in the animals' minds, indicate that ideas were not suggested to his subjects under circumstances which would have suggested them to human beings. Cole's opposite results, however, weaken Thorndike's conclusions. Further, the way in which instinctive actions are often performed by animals indicates that ideas are not present as they would be to a human being's consciousness. Human beings do some things from instinct, but the doing of them may be accompanied by ideas; a mother's care for her child involves ideas of the child's happiness or suffering, and of its future. Enteman's account of the worker wasp which, lacking other food to present to a larva, bit off a portion of one end of the larva's body and offered it to the other end to be eaten, suggests a peculiar limitation of ideas in the wasp's mind, at least while this particular function was being performed (112). The cow, which had lamented at being deprived of her calf, and on having the stuffed skin of her offspring given to her, licked it with maternal devotion until the hay stuffing protruded, when she calmly devoured the hay (279, p. 334), had perhaps experienced some dim ideas connected with her loss, but certainly her consciousness was more absorbed by the effects of present stimulation and less occupied with ideas than a human mother's would have been.

On the other hand, certain features of animal behavior are held by most people to be indications that the creatures thus acting have ideas of absent objects. Dogs and cats are supposed to dream because they snarl and twitch their muscles in sleep; but, as Thorndike has pointed out, such movements may be purely reflex and unaccompanied by any conscious

ness whatever. A dog shows depression during his master's absence, but his state of mind may be merely vague discomfort at the lack of an accustomed set of stimuli, not an idea of what he wants. A cat, indeed, once observed by the writer, did behave as a human being would do to whom an idea had occurred, when, on coming into the house for the first time after she had moved her kittens from an upper story to the ground floor, she started upstairs to the old nest, stopped half way up, turned and ran down to the new one. But errors of interpretation are possible at every turn of such observations. An attempt was made by Thorndike to test experimentally the presence of ideas in the minds of the cats he was studying by the puzzle-box method. He sat near the cage where the cats were kept, and having made sure that the cats were looking at him, he would clap his hands and say, "I must feed those cats." Aften ten seconds he would take a piece of fish, go to the cage and hold it through the wire netting; the cat, of course, would climb up and get the food. After from thirty to sixty trials the cat learned to climb up when it heard him clap his hands and speak, without waiting for him to get the fish. But it is not certain that the handclapping came thus to suggest to the cat an idea of the experimenter's taking the food and coming to the cage; rather, in the course of so many repetitions, the clapping of the hands may have become a direct stimulus to the act of climbing up, although Thorndike thinks that the ten seconds' interval rendered this improbable (393). Cole, as we have seen, has observed behavior in the raccoon that might well be regarded as involving ideas (82).

Despite the difficulty of proving that animals have memory ideas, it is not likely that any such gulf separates the human mind from that of the higher animals as would be involved in the absence from the latter of all images of past experiences.

That ideas occur in far less profusion and with far less freedom of play in the animal mind that possesses them at all than in the human mind; that even the highest animal below man lives far more completely absorbed in present stimulations than does the average man, seems also practically certain. In the lack of more definite knowledge on the subject, we may discuss a few related questions that suggest themselves with regard to, first, the primitive function of ideas; secondly, the relation of ideas to qualitative differences in sensation; and thirdly, the nature and possible origin of "movement ideas."

$93. The Primitive Function of Ideas

(1) What would be the most obvious and fundamental use of ideas to an animal? In our own experience, ideas of absent objects have, among the various functions they subserve, two that are rather definitely contrasted, which may be termed the backward and the forward reference of ideas. On the one hand, we recall past experiences purely as such; we indulge in "the pleasures of memory," letting the attention wander over trains of ideas recognized as belonging to the past. On the other hand, we form ideas of experiences we expect to have in the future, ideas which are derived, it is true, from what has happened in the past, but which involve a very different attitude on our part from that required by mere retrospection, - the attitude, namely, of anticipation, of preparing to act appropriately to the situation present in idea. Now if we ask which of these two functions of the idea is practically the more important, we cannot hesitate to say that the second is. To recall the past, except for the purpose of anticipating the future, is an intellectual luxury. As Bentley remarks, "The primary use of the image, we surmise, was to carry the organism beyond the limits of the immediate

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