Animal Behaviour

by C. Lloyd Morgan

Professor Whitman rightly regards the act of rolling into a ball as instinctive, and due to natural selection. But he does not undertake to discuss the question as to how much intelligence, if any, Clepsine may have. Nor, indeed, is it an easy matter to determine. The differential reaction according as the animal has eggs or not suggests intelligence; but it may be instinct varying according to the conditions of stimulation external and internal. The different behaviour which may be seen in different cases when a stone is turned to the light again suggests intelligence, but again may be determined directly by the conditions of stimulation. Prompted by Dr. Whitman’s observations, I endeavoured to determine whether a leech would grow accustomed to frequent gentle stimulation with a camel’s-hair brush, and cease to react under circumstances which were followed by no ill effects. But though I incline to think that this is the case, the observations were not such as to be satisfying and convincing. If intelligence be present we seem to find it in an early and rudimentary state.

Observation, we must confess, seems to afford little indication of the conditions under which intelligence first makes its appearance in the animal kingdom. And if we turn to general considerations, which at the best afford uncertain guidance, little light is thrown on the subject. If we accept the view already indicated,[71] that the nerve-centres which are concerned in the conscious control begotten of experience are independent of those primarily concerned in normal reflex action, we may perhaps believe that the simplest nervous system, worthy of the name, contains both these elements, and that in the course of the evolution of nervous systems in higher and higher grades, there go on pari passu the further differentiation of these elements, and the progressive integration of reflex and control centres into a closely connected and effective whole. Not that any expression of the facts, if such they be, in terms of an evolution formula, adds anything to our knowledge of the organic modus operandi. We know but little of the intimate nerve physiology of even the highest invertebrates. We see ample evidence of the control of behaviour in the light of individual experience. Of any detailed knowledge concerning the manner in which this control is effected we do not seem to possess more than the rude initial phases.

When we compare, however, the several grades of intelligence which observation suggests, and when we watch the conscious development of the more intelligent animals, we seem to find evidence of the growth of a system of experience, at first in very close touch with inherited modes of procedure, but gradually acquiring more of independence and freedom. Increase of the range and complexity of behaviour brings with it, not only increase in the range and complexity of experience, but also—what is, perhaps, even more essential to effective progress—greater unity and closer connection into a well-knit whole. And with this greater unity and closer connection there goes what one may term a condensation of experience by an elimination of detail and the survival of essential features repeatedly emphasized. This is analogous in the development of intelligence to the generalization and abstraction which play so important a part in the development of reason. It affords, in fact, the data which reflection utilizes in the purposive and intentional condensation and concentration of knowledge at a higher stage of mental development.

The omission of detail and the survival of the salient features is well known to us in the familiar facts of memory. We have seen thousands of sheep and oxen, no two of which are probably alike in all their external details as presented to vision. But we remember what a sheep or an ox looks like, and many of us can form a visualized image of either of these animals. This, however, is not the re-presentative image of any particular sheep or ox. It is what psychologists term a generic image. It is like a composite photograph made by superimposing on the same plate a number of individual images so that the salient features which all possess in common stand out clearly by their coincidence on the plate, while the distinctive details are but dimly presented. Thus does memory preserve the essentials common to many impressions while the distinguishing details are lost and fade, eliminated by forgetfulness. And thus in the experience which intelligence practically utilizes are the net results of a thousand particular impressions condensed in one effective image.

Condensation of experience is also effected by the elimination, under the guidance of consciousness, of those modes of behaviour which are not efficacious—a process to which Professor Mark Baldwin applies the phrase Functional Selection. There is a tendency at first to the overproduction of relatively useless actions. The multifarious random movements of the human infant, though their inexactness renders the child terribly helpless, afford a wide store of plastic material which intelligence can guide to its appropriate use. And the prolonged period of pupilage in the child is correlated with an unsurpassed range of combination and recombination of the abundant plastic material. The hereditary legacy, though it contains fewer drafts for definite and specific purposes than are placed to the credit of an animal rich in instinctive endowment, affords a far larger general fund on which intelligence may draw for the varied purposes of the freer financial existence of a rational being.

The relatively helpless young of many of the higher mammalia exhibit also much overproduction of seemingly aimless movements. But from these intelligence selects those which are of value for the purposes of life—those which experience proves to be effective. These—the relatively few—afford the motor impressions which by repetition stand out in experience, while the rest lapse from memory and are eliminated from experience as they are eliminated from practical performance. This is a great gain. Motor experience is rendered generic; the composite image that is retained is the net result of effective behaviour; and all that is valuable in the acquisitions of early life is condensed within manageable limits.

This process of rendering generic the particular items of a widening experience has a marked effect in the development of the conscious situations in the light of which behaviour is intelligently guided. It is not the master holding this whip or that ball which suggests to the dog a hiding or a scamper; it is a generic situation with interchangeable details. It is not this, that, or the other previously unseen cat that at once determines the situation for the fox terrier; the particular animal has never entered into his past experience: it is the fulfilment of the essential conditions of the generic image that is operative in behaviour. The experience of animals must inevitably become in large degree generic by the elimination of the unessential and survival in re-presentative consciousness of the salient elements in many slightly diverse situations.

Stated in terms of this conception, the familiar phenomena of mimicry are due to the fact that the mimicking form accords sufficiently well with the generic image to carry the same suggested meaning. As is well known, the model has been proved in many cases to be unpalatable or hurtful, while the mimic is in itself neither the one nor the other. The drone-fly, Eristalis, mimics the drone. And it has been urged that this cannot be a true case of mimicry, since the drone is harmless, though the female and “neuter” bees are possessed of stings. But I have satisfied myself by experiments with young birds, that (1) after experience with bees drones are avoided, and (2) that after similar experience drone-flies are also left untouched. Hence it seems that all three fall within the same generic image, the points of resemblance outweighing the differences in detail—as they do, indeed, with many men and women.

Such examples of mimicry belong to what is known as the “Batesian type”—so called after H. W. Bates, who, in 1861, discussed its occurrence among Amazonian insects in the light of the theory of natural selection. There are, however, certain groups of insects which, although themselves “protected,” possess common warning colours, causing them to resemble each other. These are sometimes classed under the head of “Müllerian mimicry”—so called after Fritz Müller, who, in 1879, first offered an explanation of the facts based on the theory of natural selection. He suggested that such mutual resemblance is advantageous to both protected forms, since it lessens the number of those which are killed by young birds and other animals while they are learning by experience what to eat and what to leave. For, as the result of careful observation, Mr. Frank Finn concludes “that each bird has to separately acquire its experience, and well remembers what it has learnt,”—a conclusion with which, as already stated, my own observations are entirely in accord. There is therefore a certain amount of destruction of even well-protected forms by young and inexperienced birds. If, then, two such forms resemble each other, the acquisition of experience is thereby facilitated and the amount of destruction reduced, on the assumption that the two fall within the same generic image. Upholders of natural selection are not, indeed, at one in accepting this explanation, and further observation is unquestionably needed. It is not improbable, however, that common protective coloration, such as the banding of yellow and black, seen in such different forms as the caterpillar of the cinnabar moth and the imago of the wasp, is of mutual utility. The following experiment was made with young chicks. Strips of orange and black paper were pasted beneath glass slips, and on them meal moistened with quinine was placed. On other plain slips meal moistened with water was provided. The young birds soon learnt to avoid the bitter meal, and then would not touch plain meal if it were offered on the banded slip. And these birds, save in two instances, refused to touch cinnabar caterpillars, which were new to their experience. They did not, like other birds, have to learn by particular trials that these caterpillars are unpleasant. Their experience had already been gained through the banded glass slips; or so it seemed. I have also found that young birds who had learnt to avoid cinnabar caterpillars left wasps untouched. Such observations must be repeated and extended. But they seem to show that one aspect of the Müllerian theory is not without some facts in support of it; and, so far as they go, they afford evidence that black and orange banding, irrespective of particular form, may constitute a guiding generic feature in the conscious situation.