The third stage is of two sorts, according as we are concerned with a reflex or with a “learned reaction”, as Dr. Watson calls it. In the case of a reflex, if it is complete at birth, a new-born infant or animal has a brain so constituted that, without the need of any previous experience, there is a connection between a certain process in the afferent nerves and a certain other process in the efferent nerves. A good example of a reflex is sneezing. A certain kind of tickling in the nose produces a fairly violent movement having a very definite character, and this connection exists already in the youngest infants. Learned reactions, on the other hand, are such as only occur because of the effect of previous occurrences in the brain. One might illustrate by an analogy which, however, would be misleading if pressed. Imagine a desert in which no rain has ever fallen, and suppose that at last a thunderstorm occurs in it; then the course taken by the water will correspond to a reflex. But if rain continues to fall frequently, it will form watercourses and river valleys; when this has occurred, the water runs away along pre-formed channels, which are attributable to the past “experience” of the region. This corresponds to “learned reactions”. One of the most notable examples of learned reactions is speech: we speak because we have learned a certain language, not because our brain had originally any tendency to react in just that way. Perhaps all knowledge, certainly nearly all, is dependent upon learned reactions, i.e., upon connections in the brain which are not part of man’s congenital equipment but are the result of events which have happened to him.
To distinguish between learned and unlearned responses is not always an easy task. It cannot be assumed that responses which are absent during the first weeks of life are all learned. To take the most obvious instance; sexual responses change their character to a greater or less extent at puberty, as a result of changes in the ductless glands, not as a result of experience. But this instance does not stand alone: as the body grows and develops, new modes of response come into play, modified, no doubt, by experience, but not wholly due to it. For example: a new-born baby cannot run, and therefore does not run away from what is terrifying, as an older child does. The older child has learned to run, but has not necessarily learned to run away; the stimulus in learning to run may have never been a terrifying object. It would therefore be a fallacy to suppose that we can distinguish between learned and unlearned responses by observing what a new-born infant does, since reflexes may come into play at a later stage. Conversely, some things which a child does at birth may have been learned, when they are such as it could have done in the womb—for example, a certain amount of kicking and stretching. The whole distinction between learned and unlearned responses, therefore, is not so definite as we could wish. At the two extremes we get clear cases, such as sneezing on the one hand and speaking on the other; but there are intermediate forms of behaviour which are more difficult to classify.
This is not denied even by those who attach most importance to the distinction between learned and unlearned responses. In Dr. Watson’s Behaviorism (p. 103) there is a “Summary of Unlearned Equipment”, which ends with the following paragraph:
“Other activities appear at a later stage—such as blinking, reaching, handling, handedness, crawling, standing, sitting-up, walking, running, jumping. In the great majority of these later activities it is difficult to say how much of the act as a whole is due to training or conditioning. A considerable part is unquestionably due to the growth changes in structure, and the remainder is due to training and conditioning.” (Watson’s italics.)
It is not possible to make a logically sharp distinction in this matter; in certain cases we have to be satisfied with something less exact. For example, we might say that those developments which are merely due to normal growth are to count as unlearned, while those which depend upon special circumstances in the individual biography are to count as learned. But take, say, muscular development: this will not take place normally unless the muscles are used, and if they are used they are bound to learn some of the skill which is appropriate to them. And some things which must certainly count as learned, such as focussing with the eyes, depend upon circumstances which are normal and must be present in the case of every child who is not blind. The whole distinction, therefore, is one of degree rather than of kind; nevertheless it is valuable.
The value of the distinction between learned and unlearned reactions is connected with the laws of learning, to which we shall come in the next chapter. Experience modifies behaviour according to certain laws, and we may say that a learned reaction is one in the formation of which these laws have played a part. For example: children are frightened of loud noises from birth, but are not at first frightened of dogs; after they have heard a dog barking loudly, they may become frightened of dogs, which is a learned reaction. If we knew enough about the brain, we could make the distinction precise, by saying that learned reactions are those depending upon modifications of the brain other than mere growth. But as it is, we have to judge by observations of bodily behaviour, and the accompanying modifications in the brain are assumed on a basis of theory rather than actually observed.
The essential points, for our purposes, are comparatively simple. Man or any other animal, at birth, is such as to respond to certain stimuli in certain specific ways, i.e. by certain kinds of bodily movements; as he grows, these ways of responding change, partly as the mere result of developing structure, partly in consequence of events in his biography. The latter influence proceeds according to certain laws, which we shall consider, since they have much to do with the genesis of “knowledge”.
But—the indignant reader may be exclaiming—knowing something is not a bodily movement, but a state of mind, and yet you talk to us about sneezing and such matters. I must ask the indignant reader’s patience. He “knows” that he has states of mind, and that his knowing is itself a state of mind. I do not deny that he has states of mind, but I ask two questions: First, what sort of thing are they? Secondly, what evidence can he give me that he knows about them? The first question he may find very difficult; and if he wants, in his answer, to show that states of mind are something of a sort totally different from bodily movements, he will have to tell me also what bodily movements are, which will plunge him into the most abstruse part of physics. All this I propose to consider later on, and then I hope the indignant reader will be appeased. As to the second question, namely, what evidence of his knowledge another man can give me, it is clear that he must depend upon speech or writing, i.e. in either case upon bodily movements. Therefore whatever knowledge may be to the knower, as a social phenomenon it is something displayed in bodily movements. For the present I am deliberately postponing the question of what knowledge is to the knower, and confining myself to what it is for the external observer. And for him, necessarily, it is something shown by bodily movements made in answer to stimuli—more specifically, to examination questions. What else it may be I shall consider at a later stage.
However we may subsequently add to our present account by considering how knowledge appears to the knower, that will not invalidate anything that we may arrive at by considering how knowledge appears to the external observer. And there is something which it is important to realise, namely, that we are concerned with a process in which the environment first acts upon a man, and then he reacts upon the environment. This process has to be considered as a whole if we are to discuss what knowledge is. The older view would have been that the effect of the environment upon us might constitute a certain kind of knowledge (perception), while our reaction to the environment constituted volition. These were, in each case, “mental” occurrences, and their connection with nerves and brain remained entirely mysterious. I think the mystery can be eliminated, and the subject removed from the realm of guesswork, by starting with the whole cycle from stimulus to bodily movement. In this way, knowing becomes something active, not something contemplative. Knowing and willing, in fact, are merely aspects of the one cycle, which must be considered in its entirety if it is to be rightly understood.
A few words must be said about the human body as a mechanism. It is an inconceivably complicated mechanism, and some men of science think that it is not explicable in terms of physics and chemistry, but is regulated by some “vital principle” which makes its laws different from those of dead matter. These men are called “vitalists”. I do not myself see any reason to accept their view, but at the same time our knowledge is not sufficient to enable us to reject it definitely. What we can say is that their case is not proved, and that the opposite view is, scientifically, a more fruitful working hypothesis. It is better to look for physical and chemical explanations where we can, since we know of many processes in the human body which can be accounted for in this way, and of none which certainly cannot. To invoke a “vital principle” is to give an excuse for laziness, when perhaps more diligent research would have enabled us to do without it. I shall therefore assume, as a working hypothesis, that the human body acts according to the same laws of physics and chemistry as those which govern dead matter, and that it differs from dead matter, not by its laws, but by the extraordinary complexity of its structure.