PLEASURE, PAIN AND THE BEGINNINGS OF

INTELLIGENCE

S. J. HOLMES

University of Wisconsin

The tendency of animals to repeat acts which result in pleasure and to discontinue or inhibit acts which bring them pain is a fundamental feature of behavior on the utility of which it would be superfluous to comment. But why do animals behave in this fortunate manner, and how did they come to acquire the faculty of so behaving? To our ordinary plain way of thinking it appears sufficient to say that a dog eats meat because he likes it, and that he runs away from the whip to avoid its painful incidence upon his integument. These acts are such natural and obvious things to do under the circumstances that to inquire why the animal does what it likes and avoids what is disagreeable may seem a sort of philosophic quibble which only a mind "debauched by learning" would think of indulging in. But a little consideration will show that we have here a real and very knotty problem, or rather set of problems, of the greatest importance to the student of genetic psychology.

There are few better illustrations of the modification of behavior through experiences of pleasure and pain than that afforded by the behavior of young chicks, which has been so well studied by Lloyd Morgan. A young chick when first hatched has the instinct to peck at all sorts of objects of about a certain size. If an object is a little too large the chick may hesitate. Should it venture to peck at the object and derive a pleasant taste from it the hesitation in the presence of similar objects becomes reduced and will finally disappear. If the chick in the course of its pecking seizes a caterpillar having a nauseous taste it is much less apt to seize a similar caterpillar a second time. The painful or un

pleasant experience it derives in some way inhibits further action towards that class of objects.

We have in this modification of instincts through the pleasurable or painful effects they produce the beginning of intelligence. The pecking, swallowing, and avoidance of certain objects are purely instinctive acts based on the chick's inherited organization. After its first experiences with pleasant or nasty caterpillars the chick is a different creature; it has learned by experience; and henceforth its acts, which at first were in a general way adaptive, become more perfectly adapted to its needs as the result of its learning. Instinct supplied the impetus to action and in a measure determined the direction of action, but intelligence refines upon the instinctive behavior and effects a closer adjustment to the environment.

In lower forms associations are formed as a rule with great slowness. Behavior is almost entirely instinctive, and the organism can be made to deviate from its stereotyped methods of action only with difficulty. It is probable that in low forms where associations of only the simplest kind can be established there is no association of ideas involved; and in fact there is no conclusive evidence of the existence of ideas even in animals quite high in the scale. Most animal learning consists in forming associations between certain sense experiences and certain actions which bring pleasure or pain. A common way of teaching an animal a trick is to try in various ways to induce it to perform the desired action and then to reward it by food or some other means of giving it pleasure. In this way the connection between the situation and the act is reinforced and the act follows more readily when the animal is placed a second time under the same conditions.

Consider the case of a cat placed in a box which can be opened by pressing down a lever or pulling a string, as in the experiments of Thorndike. If the cat is hungry and food is placed outside, the animal will probably make a vigorous effort to escape by clawing and biting in various parts of the enclosure, which are the usual instinctive methods employed in similar situations. If the right movement is hit upon and the cat gets out and secures food, it will probably make its escape more readily than before

when placed in the box a second time.

After a number of trials

the cat will come to make the right movements for escaping very soon after being placed in the box and its various useless random movements will be discontinued. The connection between the perception of the mechanism of escape in the box and the act necessary to gain its liberty comes to be more and more firmly established in the cat's brain with repeated experiences. The cat perceives a number of things in the box and performs a number of different acts but out of all these, associations are formed only between certain stimuli and those responses to them which bring pleasure to the animal.

Pleasure and pain therefore have apparently a fundamental connection with the development of intelligent responses out of instinctive activity. Were there not something to clinch or strengthen the connection between certain stimuli and the appropriate responses to them the organism might perform random movements till doomsday without being a whit better off. It is a problem therefore of fundamental importance to ascertain in what the mechanism of this ability to profit by experience essentially consists. It is not mere habit, not the mere making more permeable certain preformed connections in the brain. One act would then be just as apt to be followed up as another. Whether an act tends to be followed or not depends on what it brings to the organism. Apparently we have to do with a selective agency which preserves or repeats certain activities and rejects others on the basis of their results.

The importance of random movements lies in the fact that they offer opportunities for making favorable adjustments. For the development of intelligence they play a similar rôle to that of variations in the process of evolution. The animal that does the most exploration is the one most likely to hit upon new advantageous adjustments. In the same way intelligent adjustments as James has contended are favored by a multiplicity of instincts, especially if these instincts are of a contrary or conflicting nature, for now one and now another instinctive tendency may be reinforced in different conditions to which each may be adapted. Instinctive fear may be modified through experience so that it is

no longer attached to objects that are found to be harmless, while it may be intensified in relation to other objects that are found to be sources of injury. Where there is hesitation between the exercise of two instincts such as the tendency to pursue an animal as prey, and the instinctive fear which that animal may awaken, experience may quickly point out which proclivity is the more advantageous to follow. The pleasure-pain reaction enables an animal to select, so to speak, out of its stock of instinctive endowments those responses which are best adapted to the particular situations that confront it. It is a means of adapting instincts to new or inconstant conditions and thus of effecting a closer adaptation to the environment than that which would be possible by following purely congenital modes of response. The development of the pleasure-pain reaction marks one of the most important steps in the evolution of behavior, for the entire superstructure of intelligence in all its stages is based upon it, and it is not surprising that many writers regard it as an index of the beginning of consciousness, a point where a new entity is somehow mysteriously injected into the universe.

It is a general rule that what is pleasant is beneficial and what is painful is injurious; and, therefore, by following its desires and aversions an animal is guided in a tolerably safe course. Eating when hungry, drinking when thirsty, seeking warmth when cold, exercise when in a state of vigor, and rest when fatigued, all bring a state of satisfaction or pleasure. On the other hand, eating and drinking after a certain stage of repletion has been reached, or attaining too great a degree of warmth may be positively painful, the pain being correlated with carrying on these activities until they become injurious to the organism.

But it is well known that this correlation of the pleasant with the beneficial is not an absolute one. With complex creatures like ourselves with a multitude of different propensities and interests it is not infrequent that the pursuit of what is agreeable leads to all sorts of unfortunate consequences even of a purely physiological nature. In the lower animals where pleasure is a safer guide than among ourselves, what is pleasant is not always what is organically good. Poisonous articles may be eaten with appar

ent relish and alcoholic liquors are readily imbibed even by such primitive creatures as bees and wasps upon their very first acquaintance with these intoxicants. But aside from exceptional cases pleasure in the animal world is a sufficiently good index of what is beneficial that under conditions which ordinarily present themselves it seldom leads to injurious courses of action.

The relation between the pleasant and the beneficial is, however, probably not a primary one, and it is not improbable that it represents a connection established by natural selection, as was first maintained by Herbert Spencer.

If the states of consciousness which a creature endeavors to maintain are the correlatives of injurious actions, and if the states of consciousness which it endeavors to expel are the correlatives of beneficial actions, it must quickly disappear through persistence in the injurious and avoidance of the beneficial. In other words, those races of beings only can have survived in which, on the average, agreeable or desired feelings went along with activities conducive to the maintenance of life, while disagreeable and habitually-avoided feelings went along with activities directly or indirectly destructive of life; and there must ever have been, other things equal, the most useful and long-continued survivals among races in which these adjustments of feelings to actions were the best, tending ever to bring about perfect adjustment.

This explanation which has become widely accepted leaves a fundamental question unanswered. It does not explain why certain acts are stamped in and certain others stamped out. Of the mechanism of this process, which is the real problem involved in the pleasure-pain reaction, we are as ignorant as before. The explanation means that animals which took pleasure in following acts that brought them benefit were preserved and those that did not behave in this manner were eliminated. But why does an animal tend to repeat an act that brings it pleasure and avoid one that produces pain? It seems so natural for creatures to behave in this way that the existence of any problem here is usually unsuspected, but this is the problem that confronts us when we endeavor to obtain a clear understanding of the way in which intelligence develops out of instinct.

In the pleasure-pain response we have two problems of a quite