receives a sense

It has

consciousness. As he lies on the lawn, he stimulus, auditory or olfactory. already acquired meaning, from many a tussle with the butcher's cur. It has organic effects, and it generates a conscious situation which has acquired complexity through coalescence. As the result of this situation the head is raised, the ears pricked, and

so on,

The dog is on the alert. His attention is aroused. The muscles of neck, eyes, ears, are brought into play in such a way as to bring the senses to bear on the exciting object. He probably sees the cur through the gap in the hedge. The muscles of the frame are innervated so as to be in a state of preparation to act rapidly and forcibly. At the same time the vaso-motor system is disturbed, the heart-beat is quickened, respiration is altered; there is probably hardly an organ in the body which remains unaffected. Then the dog rushes through the hedge, and stands with bared teeth before his antagonist. A whole set of appropriate muscles are now strongly innervated. There is, perhaps, a double innervation, stimulating to activity and yet restraining from action. He bares his teeth and growls deeply. Attention is so concentrated that he heeds not, perhaps does not hear, his master's whistle. He is keenly on the alert. The blood-system, respiratory organs, and all his inner machinery are still pulsating with nervous thrills; his back is up. Then he sees his chance, and flies at his opponent. Much that he has learnt in play, and all that he has learnt in earnest, comes to his aid in the short angry scuffle. And what we call his emotion of anger spurs him on to the fight; the cowardly dog in which this is lacking or is replaced by fear is spurred to flight. Each may contribute to self-preservation, but in different ways.

.

Now, we shall not attempt to determine how the distinctively emotional elements arise. Some think they arise by a sort of irradiating nervous diffusion in the nerve-centres as a direct result of the originating stimulus. Mr. Rutgers Marshall regards them as due to the motor activities in fight or flight; Professor William James contends that they have their source in the visceral affections of heart, lungs, glands,

66

and so forth; Professor Lange attributes them to vaso-motor effects. The problem is a difficult one, and hard to determine by experiment; for we have to deal with a matter of primary genesis, of how they are at the outset introduced into the conscious situation. Experiments on animals which have already gained emotional experience cannot decide the question of genesis. Professor Sherrington, for example, has shown that, after severance of the spinal cord in the lower region of the neck, and of the vagus nerves, by which "a huge field of vascular, visceral, cutaneous, and motor reaction" were 'deprived of all connection with the nervous centre necessary to conscious response, "the emotional states of anger, delight at being caressed, fear and disgust were developed with, as far as could be seen, unlessened strength." But the avenues of connection were closed after the motor and visceral effects had played their parts in the genesis of the emotion on the hypothesis that the emotion is thus generated. Although new presentative data of this type were thus excluded, their re-presentative after-effects in the situation were not excluded. It is, moreover, an essential part of Professor James's doctrine, as I provisionally accept it, that the "expression" and the visceral and vascular efforts are independent results of stimulation in certain ways, and that these independent results are conjoined through natural selection. Suppose we sever the connection through which the one takes effect, there is no reason to expect that the manifestation of the other would cease. Professor Sherrington cut off the channels of communication with the visceral and vascular apparatus: if the channels of expression remained open there is no reason why such expression should cease.

We need not, however, for our present purpose, attempt to ascertain how the distinctively emotional characteristics arise. It is sufficient that they are presumably present in the situation. Now, as Dr. Stout well points out, the emotions

* "Experiments on the Value of Vascular and Visceral Factors for the Genesis of Emotion," Proc. Roy. Soc., vol. lxvi., pp. 390-403 (1900). "Manual of Psychology," p. 288.

generally presuppose the existence of certain specific tendencies. "The anger produced in a dog by taking away its bone presupposes the specific appetite for food. The anger produced in it by interfering with its young presupposes the specific tendency to guard and tend its offspring. So the presence of a rival who interferes with its wooing causes anger because of the pre-existence of the sexual impulse." In general, we may say that emotional states are, under natural conditions, closely associated with behaviour of biological value with tendencies which are beneficial in self-preservation or race-preservation-with actions that promote survival, and especially with the behaviour which clusters round the pairing and parental instincts. The value of the emotions in animals is that they are an indirect means of furthering survival. But how has the close association between emotional condition and the biological end it furthers been established? Again, we must say that under natural conditions it is not the sort of thing which could be acquired. And again we must urge that natural selection through survival is, apart from some theory of pre-established harmony, the only hypothesis in the field on which the close association can be explained.

There is one more point to which attention may be drawn. If there be one thing, and there certainly are not many, on which all writers on the emotions are agreed, it is as to their vagueness. They do not readily submit to definition, and cannot be described in a sentence. This is not due to any indefiniteness of biological end, nor to much indefiniteness in the mode of "expression; " it is due, rather, to an inherent dimness and haziness of psychological outline. We seem

unable to focus them and get a clear-cut result. This is, no doubt, in part due to the complexity of emotional states. But, may it not be largely due to the fact that there is no necessity for definiteness? They fulfil their purpose just as well if they are vague. It is quite necessary for the dog to have a clearcut impression of his antagonist; and, on the cognitive side. of consciousness, meaning must be in some degree definite to be of real value. But, so long as the emotion raises the

temperature, so to speak, to the boiling-point of vigorous action, it matters little what the psychological source of heat may be. If this be so, we should expect an emotional vagueness, since natural selection puts no premium upon emotional definiteness. And from this it follows, as a corollary, that, whereas we may infer that an animal's perceptual products are probably closely similar to our own, since sight, touch, hearing, smell, and taste are of value in so far as they convey definite meaning, in interpreting their feelings and emotions we have less secure grounds of inference, since all that is requisite is that there should be a sufficiently high emotional temperature to afford the conditions for definite and vigorous action.

In conclusion, then, we may say that the primary purpose of the evolution of feeling and emotion is to promote beneficial behaviour, and that the observed consonance of the psychological end of attaining satisfaction, and the biological end of securing survival, seems to be due to natural selection-is, indeed, scarcely explicable on any other naturalistic hypothesis.

A word of warning may be added. We have repeatedly spoken of biological and psychological ends. By this we mean what seems to the observer, as an interpreter of natural processes, the purpose and object of their existence. But the word "end" is often used in such a way as to imply foresight and contrivance on the part of a rational being. We have not used it in this sense. Whether the whole of nature, including animal behaviour, is driven onwards to definite ends by an underlying Cause, is a metaphysical question. It is not one on which science has any right to express an opinion one way or the other. Science deals with the phenomena; the causes of their being lie outside her province.

CHAPTER VII

THE EVOLUTION OF ANIMAL BEHAVIOUR

I. THE PHYSIOLOGICAL ASPECT

AT the outset of our inquiry, we used the word "behaviour " in a wide and comprehensive sense. Thus broadly used, I said, the term in all cases indicates and draws attention to the reaction of that which we speak of as behaving in response to certain surrounding forces or circumstances which evoke the behaviour. The behaviour of living cells is dependent on changes in their environment; that of deciduous trees, as they put forth their leaves in the spring or shed them in the autumn, is related to the change of the season; instinctive, intelligent, and emotional behaviour are called forth in response to those circumstances which exercise a constraining influence at the moment of action. Used in this comprehensive sense, the term "behaviour" neither implies nor excludes the presence of consciousness. We know from our own experience, however, that consciousness does in some cases accompany behaviour, and we infer that in many other cases it may be present. But we need a criterion of its presence to guide our inferences, and this criterion we found in the ability of living beings to profit by experience. In Dr. Stout's phraseology, if a thing seems to acquire meaning for such a being, and the behaviour is guided in accordance with such acquired meaning, we infer the presence of consciousness as supplying conditions effective in determining its course. Still this does not exclude, nay, rather it presupposes, the presence of sentience at a lower stage of evolution,