Philosophy

In the present chapter I wish to consider the processes by which, and the laws according to which, an animal’s original repertoire of reflexes is changed into a quite different set of habits as a result of events that happen to it. A dog learns to follow his master in preference to anyone else; a horse learns to know his own stall in the stable; a cow learns to come to the cow-shed at milking time. All these are acquired habits, not reflexes; they depend upon the circumstances of the animals concerned, not merely upon the congenital characteristics of the species. When I speak of an animal “learning” something, I shall include all cases of acquired habits, whether or not they are useful to the animal. I have known horses in Italy “learn” to drink wine, which I cannot believe to have been a desirable habit. A dog may “learn” to fly at a man who has ill-treated it, and may do so with such regularity and ferocity as to lead to its being killed. I do not use learning in any sense involving praise, but merely to denote modification of behaviour as the result of experience. The manner in which animals learn has been much studied in recent years, with a great deal of patient observation and experiment. Certain results have been obtained as regards the kinds of problems that have been investigated, but on general principles there is still much controversy. One may say broadly that all the animals that have been carefully observed have behaved so as to confirm the philosophy in which the observer believed before his observations began. Nay, more, they have all displayed the national characteristics of the observer. Animals studied by Americans rush about frantically, with an incredible display of hustle and pep, and at last achieve the desired result by chance. Animals observed by Germans sit still and think, and at last evolve the solution out of their inner consciousness. To the plain man, such as the present writer, this situation is discouraging. I observe, however, that the type of problem which a man naturally sets to an animal depends upon his own philosophy, and that this probably accounts for the differences in the results. The animal responds to one type of problem in one way and to another in another; therefore the results obtained by different investigators, though different, are not incompatible. But it remains necessary to remember that no one investigator is to be trusted to give a survey of the whole field. The matters with which we shall be concerned in this chapter belong to behaviourist psychology, and in part to pure physiology. Nevertheless, they seem to me vital to a proper understanding of philosophy, since they are necessary for an objective study of knowledge and inference. I mean by an “objective” study one in which the observer and the observed need not be the same person; when they must be identical, I call the study “subjective.” For the present we are concerned with what is required for understanding “knowledge” as an objective phenomenon. We shall take up the question of the subjective study of knowledge at a later stage. The scientific study of learning in animals is a very recent growth; it may almost be regarded as beginning with Thorndike’s Animal Intelligence, which was published in 1911. Thorndike invented the method which has been adopted by practically all subsequent American investigators. In this method an animal is separated from food, which he can see or smell, by an obstacle which he may overcome by chance. A cat, say, is put in a cage having a door with a handle which he may by chance push open with his nose. At first the cat makes entirely random movements, until he gets his result by a mere fluke. On the second occasion, in the same cage, he still makes some random movements, but not so many as on the first occasion. On the third occasion he does still better, and before long he makes no useless movements. Nowadays it has become customary to employ rats instead of cats, and to put them in a model of the Hampton Court maze rather than in a cage. They take all sorts of wrong turnings at first, but after a time they learn to run straight out without making any mistake. Dr. Watson gives averages for nineteen rats, each of which was put into the maze repeatedly, with food outside where the rat could smell it. In all the experiments care was taken to make sure that the animal was very hungry. Dr. Watson says: “The first trial required on the average over seventeen minutes. During this time the rat was running around the maze, into blind alleys, running back to the starting point, starting for the food again, biting at the wires around him, scratching himself, smelling this spot and that on the floor. Finally he got to the food. He was allowed only a bite. Again he was put back into the maze. The taste of the food made him almost frantic in his activity. He dashed about more rapidly. The average time for the group on the second trial is only a little over seven minutes; on the fourth trial not quite three minutes; from this point to the twenty-third trial the improvement is very gradual.” On the thirtieth trial the time required, on the average, was about thirty seconds.3 This set of experiments may be taken as typical of the whole group of studies to which it belongs. 3 Watson, Behaviorism, pp. 169–70. Thorndike, as a result of experiments with cages and mazes, formulated two “provisional laws,” which are as follows: “The Law of Effect is that: of several responses made to the same situation, those which are accompanied or closely followed by satisfaction to the animal will, other things being equal, be more firmly connected with the situation, so that, when it recurs, they will be more likely to recur; those which are accompanied or closely followed by dissatisfaction to the animal will, other things being equal, have their connections with that situation weakened, so that, when it recurs, they will be less likely to recur. The greater the satisfaction or discomfort, the greater the strengthening or weakening of the bond. “The Law of Exercise is that: Any response to a situation will, other things being equal, be more strongly connected with the situation in proportion to the number of times it has been connected with that situation and to the average vigour and duration of the connections.” We may sum up these two laws, roughly, in the two statements: First, an animal tends to repeat what has brought it pleasure; second, an animal tends to repeat what it has often done before. Neither of these laws is at all surprising, but, as we shall see, there are difficulties in the theory that they are adequate to account for the process of learning in animals. Before going further there is a theoretical point to be cleared up. Thorndike, in his first law, speaks of satisfaction and discomfort, which are terms belonging to subjective psychology. We cannot observe whether an animal feels satisfaction or feels discomfort; we can only observe that it behaves in ways that we have become accustomed to interpret as signs of these feelings. Thorndike’s law, as it stands, does not belong to objective psychology, and is not capable of being experimentally tested. This, however, is not so serious an objection as it looks. Instead of speaking of a result that brings satisfaction, we can merely enumerate the results which, in fact, have the character which Thorndike mentions, namely, that the animal tends to behave so as to make them recur. The rat in the maze behaves so as to get the cheese, and when an act has led him to the cheese once, he tends to repeat it. We may say that this is what we mean when we say that the cheese “gives satisfaction”, or that the rat “desires” the cheese. That is to say, we may use Thorndike’s “Law of Effect” to give us an objective definition of desire, satisfaction, and discomfort. The law should then say: there are situations such that animals tend to repeat acts which have led to them; these are the situations which the animal is said to “desire” and in which it is said to “find satisfaction”. This objection to Thorndike’s first law is, therefore, not very serious, and need not further trouble us. Dr. Watson considers one principle alone sufficient to account for all animal and human learning, namely, the principle of “learned reactions.” This principle may be stated as follows: When the body of an animal or human being has been exposed sufficiently often to two roughly simultaneous stimuli, the earlier of them alone tends to call out the response previously called out by the other. Although I do not agree with Dr. Watson in thinking this principle alone sufficient, I do agree that it is a principle of very great importance. It is the modern form of the principle of “association”. The “association of ideas” has played a great part in philosophy, particularly in British philosophy. But it now appears that this is a consequence of a wider and more primitive principle, namely, the association of bodily processes. It is this wider principle that is asserted above. Let us see what is the nature of the evidence in its favour. Our principle becomes verifiable over a much larger field than the older principle owing to the fact that it is movements, not “ideas”, that are to be associated. Where animals are concerned, ideas are hypothetical, but movements can be observed; even with men, many movements are involuntary and unconscious. Yet animal movements and unconscious involuntary human movements are just as much subject to the law of association as the most conscious ideas. Take, e.g. the following example (Watson, p. 33). The pupil of the eye expands in darkness and contracts in bright light; this is an involuntary and unconscious action of which we only become aware by observing others. Now take some person and repeatedly expose him to bright light at the same moment that you ring an electric bell. After a time the electric bell alone will cause his pupils to contract. As far as can be discovered, all muscles behave in this way. So do glands where they can be tested. It is said that a brass band can be reduced to silence by sucking a lemon in front of it, owing to the effect upon the salivary glands of its members; I confess that I have never verified this statement. But you will find the exact scientific analogue for dogs in Watson, p. 26. You arrange a tube in a dog’s mouth so that saliva drops out at a measurable rate. When you give the dog food it stimulates the flow of saliva. At the same moment you touch his left thigh. After a certain length of time the touch on the left thigh will produce just as much saliva without the food as with it. The same sort of thing applies to emotions, which depend upon the ductless glands. Children at birth are afraid of loud noises, but not of animals. Watson took a child eleven months old, who was fond of a certain white rat; twice at the moment when the child touched the rat, a sudden noise was made just behind the child’s head. This was enough to cause fear of the rat on subsequent occasions, no doubt owing to the fact that the adrenal gland was now stimulated by the substitute stimulus, just like the salivary glands in the dog or the trumpet player. The above illustrations show that “ideas” are not the essential units in association. It seems that not merely is “mind” irrelevant, but even the brain is less important than was formerly supposed. At any rate, what is known