Some account has already been given of the sounds made by young birds, which seem to be instinctive and to afford an index of the emotional state at the time of utterance. That in many cases they serve to evoke a like emotional state and correlated expressive behavior in other birds of the same brood cannot be questioned. The alarm note of a chick will place its companions on the alert; and the harsh "krek" of a young moor-hen, uttered in a peculiar crouching attitude, will often throw others into this attitude, though the maker of the warning sound may be invisible. That the cries of her brood influence the conduct of the hen is a matter of familiar observation; and that her danger signal causes them at once to crouch or run to her for protection is not less familiar. No one who has watched a cat with her kittens, or a sheep with her lambs, can doubt that such "dumb animals" are influenced in their behavior by suggestive sounds. The important questions are, how they originate, what is their value, and how far such intercommunication—if such we may call it—extends.
There can be but little question that in all cases of animals under natural conditions such behavior has an instinctive basis. Though the effect may be to establish a means of communication, such is not their conscious purpose at the outset. They are presumably congenital and hereditary modes of emotional expression which serve to evoke responsive behavior in another animal—the reciprocal action being generally in its primary origin between mate and mate, between parent and offspring, or between members of the same family group. And it is this reciprocal action which constitutes it a factor in social evolution. Its chief interest in connection with the subject of behavior lies in the fact that it shows the instinctive foundations on which intelligent and eventually rational modes of intercommunication are built up. For instinctive as the sounds are at the outset, by entering into the conscious situation and taking their part in the association-complex of experience, they become factors in the social life as modified and directed by intelligence. To their original instinctive value as the outcome of stimuli, and as themselves affording stimuli to responsive behavior, is added a value for consciousness in so far as they enter into those guiding situations by which intelligent behavior is determined. And if they also serve to evoke, in the reciprocating members of the social group, similar or allied emotional states, there is thus added a further social bond, inasmuch as there are thus laid the foundations of sympathy.
"What makes the old sow grunt and the piggies sing and whine?" said a little girl to a portly, substantial farmer. "I suppose they does it for company, my dear," was the simple and cautious reply. So far as appearances went, that farmer looked as guiltless of theories as man could be. And yet he gave terse expression to what may perhaps be regarded as the most satisfactory hypothesis as to the primary purpose of animal sounds. They are a means by which each indicates to others the fact of his comforting presence; and they still, to a large extent, retain their primary function. The chirping of grasshoppers, the song of the cicada, the piping of frogs in the pool, the bleating of lambs at the hour of dusk, the lowing of contented cattle, the call-notes of the migrating host of birds—all these, whatever else they may be, are the reassuring social links of sound, the grateful signs of kindred presence. Arising thus in close relation to the primitive feelings of social sympathy, they would naturally be called into play with special force and suggestiveness at times of strong emotional excitement, and the earliest differentiations would, we may well believe, be determined along lines of emotional expression. Thus would originate mating cries, male and female after their kind; and parental cries more or less differentiated into those of mother and offspring, the deeper note of the ewe differing little save in pitch and timbre from the bleating of her lamb, while the cluck of the hen differs widely from the peeping note of the chick in down. Thus, too, would arise the notes of anger and combat, of fear and distress, of alarm and warning. If we call these the instinctive language of emotional expression, we must remember that such "language" differs markedly from the "language" of which the sentence is the recognized unit.
It is, however, not improbable that, through association in the conscious situation, sounds, having their origin in emotional expression and evoking in others like emotional states, may acquire a new value in suggesting, for example, the presence of particular enemies. An example will best serve to indicate my meaning. The following is from H. B. Medlicott:
In the early dawn of a grey morning I was geologizing along the base of the Muhair Hills in South Behar, when all of a sudden there was a stampede of many pigs from the fringe of the jungle, with porcine shrieks of sauve qui peut significance. After a short run in the open they took to the jungle again, and in a few minutes there was another uproar, but different in sound and in action; there was a rush, presumably of the fighting members, to the spot where the row began, and after some seconds a large leopard sprang from the midst of the scuffle. In a few bounds he was in the open, and stood looking back, licking his chops. The pigs did not break cover, but continued on their way. They were returning to their lair after a night's feeding on the plain, several families having combined for mutual protection; while the beasts of prey were evidently waiting for the occasion. I was alone, and, though armed, I did not care to beat up the ground to see if in either case a kill had been effected. The numerous herd covered a considerable space, and the scrub was thick. The prompt concerted action must in each case have been started by the special cry. I imagine that the first assailant was a tiger, and the case was at once known to be hopeless, the cry prompting instant flight, while in the second case the cry was for defense. It can scarcely be doubted that in the first case each adult pig had a vision of a tiger, and in the second of a leopard or some minor foe.
If we accept Mr. Medlicott's interpretation as in the main correct, we have in this case: (1) common action in social behavior, (2) community of emotional state, and (3) the suggestion of natural enemies not unfamiliar in the experience of the herd. It is a not improbable hypothesis, therefore, that in the course of evolution the initial value of uttered sounds is emotional; but that on this may be grafted in further development the indication of particular enemies. If, for example, the cry which prompts instant flight among the pigs is called forth by a tiger, it is reasonable to suppose that this cry would give rise to a representative generic image of that animal having its influence on the conscious situation. But if the second cry, for defense, was prompted sometimes by a leopard and sometimes by some other minor foe, then this cry would not give rise to a representative image of the same definiteness. Whether animals have the power of intentionally differentiating the sounds they make to indicate different objects is extremely doubtful. Can a dog bark in different tones to indicate "cat" or "rat," as the case may be? Probably not. It may, however, be asked why, if a pig may squeak differently, and thus, perhaps, incidentally indicate on the one hand "tiger" and on the other hand "leopard," should not a dog bark differently and thus indicate appropriately "cat" or "rat"? Because it is assumed that the two different cries in the pig are the instinctive expression of two different emotional states, and Mr. Medlicott could distinguish them; whereas, in the case of the dog, we can distinguish no difference between his barking in the one case and the other, nor do the emotional states appear to be differentiated. Of course there may be differences which we have failed to detect. What may be regarded, however, as improbable is the intentional differentiation of sounds by barking in different tones with the purpose of indicating "cat" or "rat."
Such powers of intercommunication as animals possess are based on direct association and refer to the here and the now. A dog may be able to suggest to his companion the fact that he has descried a worriable cat; but can a dog tell his neighbor of the delightful worry he enjoyed the day before yesterday in the garden where the man with the biscuit tin lives? Probably not, bark he never so expressively.
From the many anecdotes of dogs calling others to their assistance or bringing others to those who feed them or treat them kindly, we may indeed infer the existence of a social tendency and of the suggestive effects of behavior, but we cannot derive conclusive evidence of anything like descriptive communication.
Such intentional communication as is to be found in animals, if indeed we may properly so call it, seems to arise by an association of the performance of some act in a conscious situation involving further behavior for its complete development. Thus the cat which touches the handle of the door when it wishes to leave the room has had experience in which the performance of this act has coalesced with a specific development of the conscious situation. The case is similar when your dog drops a ball or stick at your feet, wishing you to throw it for him to fetch. Still, it is clear that such an act would be the perceptual precursor of the deliberate conduct of the rational being by whom the sign is definitely realized as a sign, the intentional meaning of which is distinctly present to thought. This involves a judgment concerning the sign as an object of thought; and this is probably beyond the capacity of the dog. For, as Romanes himself says, "It is because the human mind is able, so to speak, to stand outside of itself and thus to constitute its own ideas the subject-matter of its own thought that it is capable of judgment, whether in the act of conception or in that of predication. We have no evidence to show that any animal is capable of objectifying its own ideas; and therefore we have no evidence that any animal is capable of judgment."