Animal Life and Intelligence

by C. Lloyd Morgan

1.	{	a. Caterpillars spinning cocoons.
		b. Instincts of social hymenoptera.
2.	{	a. Drumming of snipe.
		b. Procedure of Queensland bower-bird.
3.	{	a. Ants forming nests in trees in flooded parts of Siam.
		b. Instinctive fear of man.

In speaking of the instinct of caterpillars spinning cocoons as unintelligent, I am regarding the final purpose of the activity. Intelligence may very possibly have come into play in modifying the details of procedure. In giving the drumming of snipe as an example of unintelligent activities furthered by selection, I am assuming that it has a sexual import, and that the activity correlated with a narrowing of the tail-feathers was not, in its inception, intelligently performed with the object of exciting sexual appetence in the hen. The case of the ants of Siam is given by Mr. Romanes,[JO] on the authority of Lonbière, who says "that in one part of that kingdom, which lies open to great inundations, all the ants made their settlements upon trees; no ants' nests are to be seen anywhere else." Now, this modification of habits may have been the result of intelligence; or it may have been forced upon the ants by circumstances. The floods drove them on to the trees; the instinctive impulse to build a settlement was imperative; hence the settlement had to be formed on the trees, because the ground was flooded. The difficulty of ascertaining whether intelligence has or has not been a factor is simply part of the inherent difficulty of comparative psychology—a difficulty on which sufficient stress has already been laid in an earlier chapter.

The great majority of the instinctive activities of animals have arisen through a co-operation of the factors, and it is exceedingly difficult in any individual case to assign to the factors their several values.

And here we must once more notice that the separation off of the instinctive activities from the other activities of animals is merely a matter of convenience in classification. In the living organism the activities—automatic actions, reflex actions, incompletely and perfectly established instincts, habits, and intelligent activities—are unclassified and commingled. They are going on at the same time, shading the one into the other, untrammelled by the limits imposed by a scientific method of treatment.

Once more, too, we must notice that the activities of animals are essentially the outcome and fulfilment of emotional states. When the emotional sensibility is high, the resulting activities are varied and vigorous. As we have before seen, this high state of emotional sensibility is correlated with a highly charged and sensitive condition of the organic explosives elaborated by the plasmogen of the cells. After repose, and at certain periodic times, this state of exalted sensibility is apt to occur. It is exemplified in the so-called instinct of play, which manifests itself in varied activities in the early morning, in early life, and in the returning warmth of spring—at such times, in fact, as the life-tide is in full flood.

But perhaps the activities which result from a highly wrought state of sensibility are best seen at the periodic return of sexual appetence or impulse in animals of various grades of life and intelligence. Many organisms, at certain periods of the year, and in presence of their mates, are thrown into a perfect frenzy of sexual appetence. The love-antics of birds have been so frequently described that I will merely quote from Darwin[JP] Mr. Strange's account of the satin bower-bird: "At times the male will chase the female all over the aviary, then go to the bower, pick up a gay feather or a large leaf, utter a curious kind of note, set all his feathers erect, run round the bower, and become so excited that his eyes appear ready to start from his head; he continues opening first one wing, and then the other, uttering a low, whistling note, and, like the domestic cock, seems to be picking up something from the ground, until at last the female goes gently towards him." Instances might be quoted from almost all classes of the animal kingdom. Many fish display "love-antics," for example, the gay-suited, three-spine stickleback, whose excitement is apparently intense. Newts display similar activities. Even the lowly snail makes play with its love-darts (spiculæ amoris), practical tangible darts of glistening carbonate of lime. Mr. George W. Peckham has recently described[JQ] the extraordinary "love-dance" of a spider (Saitis pulex). "On May 24 we found a mature female, and placed her in one of the larger boxes; and the next day we put a male in with her. He saw her as she stood perfectly still, twelve inches away; the glance seemed to excite him, and he at once moved towards her; when some four inches from her he stood still, and then began the most remarkable performances that an amorous male could offer to an admiring female. She eyed him eagerly, changing her position from time to time, so that he might be always in view. He, raising his whole body on one side by straightening out the legs, and lowering it on the other by folding the first two pairs of legs up and under, leaned so far over as to be in danger of losing his balance, which he only maintained by sidling rapidly towards the lowered side. The palpus, too, on this side was turned back to correspond to the direction of the legs nearest it. He moved in a semicircle for about two inches, and then instantly reversed the position of the legs, and circled in the opposite direction, gradually approaching nearer and nearer to the female. Now she dashes towards him, while he, raising his first pair of legs, extends them upward and forward as if to hold her off, but withal slowly retreats. Again and again he circles from side to side, she gazing towards him in a softer mood, evidently admiring the grace of his antics. This is repeated until we have counted a hundred and eleven circles made by the ardent little male. Now he approaches nearer and nearer, and when almost within reach whirls madly around and around her, she joining and whirling with him in a giddy maze. Again he falls back and resumes his semicircular motions, with his body tilted over; she, all excitement, lowers her head and raises her body, so that it is almost vertical; both draw nearer; she moves slowly under him, he crawling over her head, and the mating is accomplished."

It can scarcely be doubted that such antics, performed in presence of the female and suggested at sight of her, serve to excite in the mate sexual appetence. If so, it can, further, scarcely be doubted that there are degrees of such excitement, that certain antics excite sexual appetence in the female less fully or less rapidly than others; yet others, perhaps, not at all. If so, again, it can hardly be questioned that those antics which excite most fully or most rapidly sexual appetence in the female will be perpetuated through the selection of the male which performs them. This is sexual selection through preferential mating. And, I think, the importance of these activities, their wide range, and their perfectly, or at any rate incompletely instinctive nature, justifies me in emphasizing this factor in the origin of instinctive activities. It has hitherto, I think, not received the attention it deserves in discussions of instinct.

A few more words may here be added to what has already been said on the influence of intelligence on instinct. The influence may be twofold—it may aid in making or in unmaking instincts. We have seen that instincts may be modified through intelligent adaptation. A little dose of judgment, as Huber phrased it, often comes into play. The cell-building instinct of bees is one which is remarkably stereotyped; and yet it may be modified in intelligent ways to meet special circumstances. When, for example, honey-bees were forced to build their comb on the curve, the cells on the convex side were made of a larger size than usual, while those on the concave side were smaller than usual. Huber constrained his bees to construct their combs from below upwards, and also horizontally, and thus to deviate from their normal mode of building. The nest-construction of birds, again, may be modified in accordance with special circumstances. And, perhaps, it is scarcely too much to say that, whenever intelligence comes on the scene, it may be employed in modifying instinctive activities and giving them special direction.

Now, suppose the modifications are of various kinds and in various directions, and that, associated with the instinctive activity, a tendency to modify it indefinitely be inherited. Under such circumstances intelligence would have a tendency to break up and render plastic a previously stereotyped instinct. For the instinctive character of the activities is maintained through the constancy and uniformity of their performance. But if the normal activities were thus caused to vary in different directions in different individuals, the offspring arising from the union of these differing individuals would not inherit the instinct in the same purity. The instincts would be imperfect, and there would be an inherited tendency to vary. And this, if continued, would tend to convert what had been a stereotyped instinct into innate capacity; that is, a general tendency to certain activities (mental or bodily), the exact form and direction of which is not fixed, until by training, from imitation or through the guidance of individual intelligence, it became habitual. Thus it may be that it has come about that man, with his enormous store of innate capacity, has so small a number of stereotyped instincts.

But while intelligence, displayed under its higher form of originality, may, in certain cases, lead to all-round variation, tending to undermine instinct and render it less stereotyped, intelligence, under its lower form of imitation, has the opposite tendency. For young animals are more likely to imitate the habits of their own species than the foreign habits of other species, and such imitation would therefore tend towards uniformity.