ANIMAL BEHAVIOUR. To give a plain tale of this or that instance of animal behaviour is not easy. The language in which it is described nearly always introduces words which imply more than can be seen. And what most people want is not only a plain tale of that which one can see, but an interpretation in terms of which one may, in some wise, account for the observable behaviour.
(I) Carmine particles are suspended in the water in which the unicellular organism, stentor, is under observation. At first the behaviour is not visibly affected. After a while the animalcule turns this way and that. Then there is reversal of the ciliary action in the wreath that surrounds the mouth. Later on, the stentor withdraws into its sheath. Then it breaks away and swims off. Such is a plain tale of facts which Professor Jennings has placed on record.
(2) Under experimental conditions some chicks, a few days old, are quietly feeding. Maggots seem specially attractive. Each time a selected chick is about to seize a maggot a toy pistol is fired at some little distance, out of sight. Each time the chick starts and turns aside. After about a dozen repetitions of this procedure the pistol is no longer fired. None the less there is aversive behaviour at sight of a maggot. During the next day no maggots are eaten by this chick.
(3) Suitably placed before an orang-utan, Julius, are nine compartments. Food can be obtained by passing through one of them. The entrance doors are visibly open or shut. Matters are so arranged that, on different occasions, or "settings," three con secutive doors are open-2, 3, 4 ; 7, 8, 9 ; and so on. But only by entering the left-hand door of the three, and passing through this compartment, can food be obtained. In some ten observations on each of 24 days there is no difference of behaviour in relation to "this" rather than "that" of the three open doors. On the 25th day the left-hand door is entered on each of the ten settings. On the following day a series of ten settings, different from those of the preceding days, is responded to promptly, readily, and without a mistake. Further details are given by Prof. Yerkes.
There are many who urge that, so long as we keep within the domain of inductive science as they define it, this is all that we are justified in saying. But there are others who urge that in saying this and no more one does not really "account for" what happens in this or any other instance of animal behaviour. To account for what happens, it is said to be imperative that an answer be given to the question : through the operation of what agency, as efficient cause, is this or that manner of behaving to be explained? When this question is raised one enters a region of acute con troversy. But need we enter this region? May it not be better to shun controversy by discussing animal behaviour in a de limited domain of inquiry—a domain which is common to dis putants on this side and on that? If so we should formulate concisely what lies within this delimited domain. It is for us that domain in which the canon of interpretation runs : given such and such relations of the animal to surrounding events, and given such and such relations of events within the organism, then such and such is the observable behaviour.
In what was said above with regard to an interpretation of the behaviour of stentor we kept within this domain. It may, however, be objected that such an interpretation is wholly in terms of physical conditions external to the organism, and of physiological states within it. Is that so? Does our statement imply that physical and physiological relations only are present, and that mental relations, in some comprehensive sense of the word "mental," are absent? It does not. That would imply that we are quite arbitrarily to exclude from our survey of animal behaviour a kind of relatedness that is assuredly inferable from much of the behaviour of more highly developed organisms.
It is here that difficulty attends our starting with the behaviour of stentor rather than with that of the orang-utan. There are few who deny that mental relations have being and play some part in the behaviour of the anthropoid apes. There are some who say that there is no evidence of any relations of the mental kind in the unicellular organisms. We must, however, accept some hypoth esis on which to conduct our enquiry. As an hypothesis, frankly entertained as such, let us proceed on the supposal that relations of the mental kind are present in all instances of animal behaviour. For lack of better words, let us say that in stentor there is some "percipience" having reference to external events, and some "sentience" concomitant with the internal changes of state. Let us assume that in any living animal there are not only relations of the physical and physiological kind, but also relations of the mental kind. Nay more, let us chiefly con sider the part that mental relations play in animal behaviour. The emphasis here is on relations. Efficient causality is not within our province. Let us keep to our canon of interpretation, and say: Given such and such relations, physical and mental (a) of the organism to its surroundings, and (b) within the organism, such and such is the observable behaviour. On this hypothesis, since relations of both kinds are always present, the question does not arise : Would the behaviour be just the same were either kind of relatedness absent? Ex hypothesi neither kind is absent in any instance of animal behaviour.
It may, however, be said : Even if it be granted that in all instances of animal behaviour both kinds are in being, it does not follow that the presence of mental relations makes any dif ference in the course of events. The implication here is that the presence of physical relations does make a difference. But what is meant by the ambiguous expression "make a difference"? In one sense whether they do or do not make a difference, in the case of stentor, or the chick, or Julius the orang, is a question of evidence—or more strictly the question how best to interpret the available evidence. But in another sense it is the operation of some Force that is invoked to explain what makes the difference. Such explanation lies beyond our purview, since the concept of Force in this sense—any Force, whether mechanical or vital or other—is borrowed from the vocabulary of a philosophy which deals with efficient causality. One may hazard the assertion that this concept has no place in modern physics as a branch of science. In any case it has no place in our canon of interpreta tion. In formulating such a canon one's aim is (I) to include all kinds of relations which may be inferred from what we observe in the whole range of animal behaviour ; and (2) to exclude from our inquiry an issue that is the storm-centre of much philosophical controversy.
We now pass to the behaviour of the chick as an instance of what may be called "secondary behaviour." We have here a much more highly developed animal in which there is a "synaptic" nervous system. When we try to get down to essentials we must ask : What is the salient difference which distinguishes secondary from primary behaviour? So far as mental relations are con cerned, may we not find a clue in the further supposal that sec ondary behaviour implies reference that is no longer confined to the moment of receipt of physical influence? The hypothesis then is that there is not only percipient reference on receipt of in fluence now, on this occasion, but also what we may call "supple mentary reference" to the like of that which was the source of such influence on some previous occasion or occasions. To per cipience is added that "meaning"—in some sense of this word— which raises bare percipience to the level of naïve perception. Then we may say : Given this mode of mental relatedness, such and such modification of the course of behaviour is observed.
Apply this to the selected instance of secondary behaviour. On the first occasion, when the pistol was fired, there was, we assume, percipience and sentience with which a specific mode of primary behaviour was linked up in accordance with the hereditary nature of the bird and the build of its nervous system. On this first occasion, however, there is no call to go beyond percipience and sentience as relations of the mental kind. The behaviour described as "starting and turning aside" is, on the first occasion, primary. And in so far as on subsequent occasions like behaviour is repeated da capo, it is still of the primary order.
But on some subsequent occasion the maggot is avoided at sight. The aversive behaviour—an observable change of attitude— is in evidence in the absence of the external conditions which on the first occasion elicited this specific response. Furthermore, the behaviour we describe as "seizing and swallowing," primary in origin, which on previous occasions was elicited at sight of the maggot, is no longer elicited. There is thus an observable dif ference of behaviour on earlier and on later occasions. On earlier occasions under receipt of physical influence we have this mode of stimulation and percipience, linked with this mode of behaviour and concomitant "enjoyment" in thus behaving. But on later occasions we have this mode of stimulation (visual) linked with that mode of behaviour (aversive).
What here calls for interpretation is the switching off of respon sive action in such wise as to give this observable outcome. It is clear that the interpretation should be sought in some internal conditions within the organism that is in receipt of stimulation. For under closely similar external conditions the behaviour is different on the first and on some later critical occasion. This sets a problem for physiology. The switching off seems in large meas ure to be interpretable in terms of the opening up of functionally new routes—secondary connecting-routes—in the central nervous system. This is discussed under the heading of the "conditioned reflex." One cannot enlarge upon it here. Two things may be noted : ( I) that the connection is such as to link the afferent or receptor limb of "this" primary route with the efferent or effector limb of "that" primary route; (2) that the reorganisation effected in this way is acquired in the course of individual life.
However it be interpreted physiologically there is some specific change within the organism—almost certainly within the synaptic nervous system, probably only when there is a nervous system of this type—such as to provide for a new distribution of behaviour-output on receipt of physical influence on the sensory receptors. And this redistribution of output, distinctive of the wide range of secondary behaviour, is relatively abiding. But the more primitive distribution, initially inherited, may at times be reinstated. The old primary "this-to-this" routes seem to be re opened in certain states of the organism.
To the internal states and the part they play in animal behaviour we shall have presently to direct consideration. Here it is in place to emphasize two things: (i) that the redistribution of behaviour output entails a redistribution of naïve perceptual reference ; (2) that the latter redistribution is of the cognitive type, with sup plementary reference and the acquisition of fuller "meaning." In the naïve perception of animals this "meaning" is probably referred to the external situation as a whole. The analysis of this whole into "objects" in relation to each other and to the percipient, and its resynthesis "as a whole," comes only with reflective thought. None the less behaviour is commonly centred on something salient in the external situation which we reflectively recognize as an object in relation to its surroundings and to us. In the genesis of objective reference in the animal, as in the human infant, primary behaviour thereto leads and carries with it such "meaning" for further behaviour as the secondary step in advance entails.
In the selected instance of secondary behaviour, we have, in effect, distinguished (a) the external situation to which there is perceptual reference on receipt of physical influence therefrom, and (b) the internal situation—the existing condition and state of the organism. What seems to be essential is that the chick behaves as if a sound-shock formed part of the external situation, although there is no receipt of any such physical influence. We resort, therefore, in accordance with the method of science, to hypothesis. We ask : Is there not in the internal situation supple mentary reference to something more than is physically present in the existing external situation? If so that "something more" is what we speak of as "meaning"—practical meaning for the guidance of behaviour.
Of course it may be said that on later critical occasions the chick "remembers" the sound-shock received on prior occasions; or that a sound-shock is present in "expectation." Under suitable definitions such language is permissible. In us, however, memory implies reflective reference to incidents dated in the conceptualised past ; and expectation implies reference to incidents in the future as we conceive that it will be. Hence it is better in discussing animal behaviour to use words of less reflective import. It is well to avoid the word "purpose," since this word is specially ear marked by some controversialists to emphasize the concept of mental agency. Even the word "meaning" is likely to suggest some tinge of that reflective significance which it commonly car ries in current speech. Since, however, the animal lives forward, what has been spoken of as supplementary reference (to avoid reflective implications) has presumably "prospective meaning" in the sense that, to be of practical avail the reference is to that which, through behaving forward, will be secured or avoided.
But the question still remains : How is it that certain events which form part of the internal situation, and are interpretable as due to excitation from within via connecting neurone-routes how is it that these events, in their mental relations, carry supple mentary reference to the external situation? All that one can say is that there seems call for the supposal that they do so in animals as in us. If these events, whatever they may be, carry percipient reference when they are initially instated from without, it is not unreasonable to suppose that they retain like reference when their likes are subsequently reinstated through excitation from within.
The Behaviour of the Orang. Foreplans of Action.—In the earlier days of the life of any animal in which a synaptic nervous system has been evolved, there accompanies progressive "conditioning," progressive expansion of "prospective meaning." In later days this reaches such level of attainment as the status of organism permits. The chief turning-point in the evolution of animal behaviour is the critical passage in mental reference from primary to secondary. But when the secondary comes, the primary does not go. In all perception there is a central core of percipience.
In some animals, however, behaviour is raised to a higher level. This is illustrated by the procedure of Julius the orang. Here the presumptive evidence suggests that on some critical occasion there is what one may speak of as a "mental foreplan of action." It arises in the internal situation. But it has reference to the external situation as objectively "in mind" at the time-being.
The physiological counterpart of this higher form of reference seems, from the work of Professor Bianchi and others, to be, in mammals, a "conditioned" nexus of interconnecting neurone-routes in the frontal region of the cerebral cortex. This statement is necessarily somewhat technical. The point for emphasis is that we may infer a gradually acquired structural plan in a specialized part of the brain, which takes referential form pretty suddenly, as a foreplan of the objective situation ; and that this mental foreplan thereafter serves to guide behaviour in like situations.
There is little question that a cognitive attitude of this sort reaches a higher level in such apes as the orang and the chim panzee than it does in the monkeys. But whether this step in advance involves something new in principle or only added com plexity is open to question. A good deal lower in the mammalian scale, it is difficult to interpret such behaviour of the rat, as has recently been described with admirable care by Professor McDougall, save on the hypothesis of foreplans of action. More questionable is the presumptive evidence of such mental plans of action in birds—partly because in their later life the major episodes seem so largely to be modes of behaviour in which hereditary rather than acquired factors are dominant.
It should be remembered that all behaviour, in detail if not in its secondary integration, is so to speak built to the plan of the organism that behaves. This is so even in stentor. It is so in all primary behaviour. But when the rubicon of the secondary is overpassed there seem to be two—no doubt quite probably more than two—critical "moments" of mental advance correlated with physiological advance ; first, that at which reference becomes supplementary and prospective, and thereafter the "crystallizing out" of such reference in a mental foreplan of action. It is the task of comparative neurology and of comparative psychology (q.v.) to work out the details. The careful observations of Pro fessor Yerkes, Dr. Kohler, and others, have shown how highly developed in the anthropoid apes is supplementary reference to a complex external situation in presence of which they behave, as we infer, with a foreplan in mind; and how nicely adapted to special circumstances are many of their feats of skill. It may be that some apes have overpassed the next critical stage in onward advance—that in which action is not only carried out to a suc cessful outcome, but is interpreted in a reflective "framework of reference" under conceptual thought. This must be kept in view as an open possibility. But, as at present advised, the writer is of opinion that, on the available evidence, in man only is reflective thought developed. If so its interpretation does not fall within the scope of a discussion of animal behaviour.
On the physiological side we have seen that interpretation of the internal situation lays stress on the provision in a synaptic nervous system for conditioned response to stimulation. So too in the frontal lobes of the mammalian brain there is provision for an acquired nexus of neurone-routes. From such more or less abiding "conditioning" of the central nervous system let us dis tinguish the more labile internal state of the animal. The internal state then denotes the changing physiological poise of the organism as a whole at some given time. This is not only in a general way dependent on the reciprocal interaction (however brought about) of all the organs and tissues on each other; it is dependent in a special way on the influence of the internal secretions of certain endocrine glands transmitted by the blood stream to the fluid in which the tissues are bathed. Their influence on all that inter venes, including the passage of nerve impulses along neurone routes, between receipt of stimulation and overt behaviour con sequent thereon, is subtle and penetrating. It is not improbable that changes of state or physiological poise are subject to heredi tary transmission and thus modify the number of occasions requisite for the acquisition of a conditioned response.
One cannot follow up these intricate clues to physiological in terpretation. The mental concomitant of the internal state of the body is sentience and the affective enjoyment founded thereon. It becomes integrated as that which may be spoken of as the "self of enjoyment." We must take for granted that in animals, as in us, it is pleasurably toned or the reverse. We want to get at that which is essential in principle with respect to the role that is played by internal states. Here and now, while they are in being, they raise or depress the vigour of animal behaviour, and, by differentially raising or depressing, they modify the course of that behaviour. The stress is on here and now. It matters not whether cognitive reference be prospective, or whether a foreplan of future action be, or be not, in being. What matters is the state of the organism; and that state is here and now. Here and now is the behaviour the current course of which is felt as enjoyment in behaving. Here and now, too, is enjoyment in perceiving. It is only that to which perceiving has reference that is other than here and now. The affective state, in animals as in us, is always that of the current time-being.
We have sought to distinguish (I) the plain tale of the be haviour we observe; (2) the cognitive reference with which we credit the animal; (3) the affective state which may be inferred. But we often use one word to do duty for all three. One says, for example, that some male bird shows "hostility" when another male crosses the bounds of his territory. Under this one word is comprised (I) how he behaves; (2) his cognitive attitude, prob ably on later occasions with prospective reference to the further behaviour of the "intruder"; (3) what he "feels like" then and there. This last is the affective state as such. The point for emphasis is that this affective state—which we can only describe in terms of what we "feel like" on what we deem to be analogous occasions—is here and now, and if not here and now leaves be haviour "unaffected." instinct and Intelligence in Animals.—For popular thought the leading question with respect to any instance of animal behaviour takes the form: Is it instinctive or intelligent? The word "instinctive" is here commonly applied to an approximately invariable manner of behaving that is not "learnt" in the course of individual life, as contrasted with the more variable manner of behaving which is so learnt and which therefore betokens intel ligence on the part of the animal.
To account for intelligent behaviour it used to be deemed sufficient to say that what is learnt by the animal is the outcome of that profiting by experience with which we are familiar in our own life. To account for instinctive behaviour there was recourse either to inherited experience or to inherited structural organiza tion of the nervous system. Some said : Just as intelligent habits are acquired and become automatic in the course of individual life, so have the more typical instincts been similarly acquired and have become automatic in the course of racial life. Others said : Just as the hereditary mode of development of the plumage of a bird is interpretable biologically, so is the hereditary manner in which that plumage is displayed on some first occasion of court ship biologically interpretable.
Discussion on lines such as these is now somewhat out of date. More up to date, as things are, is the discussion of instinct and intelligence in terms of diverse expressions of that elan vital which —as some assert, and others roundly deny—must be invoked to explain all that happens in any living creature. Thus is raised the controversial issue which it has been our aim to avoid by delimiting the domain of our inquiry.
Apart, however, from this further issue, the words "instinctive" and "intelligent" will for long continue in popular use with signification best inferred from the context. The context for most people is seldom that of stentor, or even that of the sea-anemone or starfish. It is generally that of behaviour of animals in which both sensory and motor organs are well developed, and in which there is a highly organized (technically "synaptic") nervous system. It is generally also a context in which arises the question : Is the behaviour in evidence instinctive or intelligent? This im plies some doubt as to which it is. If certain salient features of the behaviour are clearly the outcome of prior experience acquired in the course of individual life, the procedure is spoken of as that of an intelligent animal—and the more nicely adaptive it is in this way, the more intelligence is attributed to the animal. If, on the other hand, the predominant feature is not the outcome of prior experience, it is called instinctive—and the more adaptive it is in an inherited and unlearnt way, the more typically instinc tive, rather than merely reflex, is such behaviour.
If this gives adequate expression to the popular attitude, how does it stand in relation to the foregoing treatment? The behav iour commonly called instinctive, in so far as it is unconditioned and carries no supplementary reference, is that which has been spoken of as "primary" in the context of such animals as birds for example. The behaviour commonly regarded as betokening intelligence is at a fairly high level of that which has been spoken of as "secondary," and more especially that which seems to imply a foreplan of action.
BIBLIOGRAPHY. See Comparative Psychology ; also H. S. Jennings, Bibliography. See Comparative Psychology ; also H. S. Jennings, Behaviour of the Lower Organisms (1906) ; C. Lloyd Morgan, Life, Mind and Spirit, Lectures II., IV. and VII. (1926) ; R. M. Yerkes, The Mental Life of Monkeys and Apes (1916) ; I. R. Pavlov, Condi tioned Reflexes (1927) ; L. Bianchi, The Mechanism of the Brain and Function of the Frontal Lobes (Eng. trans., 1922). (C. LL. M.)