§ 5. Free Adaptation to Varying Conditions. — We have just seen that perceptual process exhibits adaptive variation, according as activity is successful or unsuccessful. But, besides this, we find in it also adaptive variation in accordance with varying external conditions. We may quote first a simple and rudimentary example from Lloyd Morgan. "I took a young pheasant, which had been hatched some time in the night, from the incubator drawer at nine o'clock in the morning. He was very unsteady on his legs, so I held him in my hands, and tried to induce him to peck at a piece of egg yolk held in a pair of forceps. He did not do so; but he followed, with his head, every movement of the object in a narrow circle about two inches in front of his beak. Simple as the action seems, it shows a striking example of congenital coordinated movements accurately related to movements in the visual field, the whole performed without any possibility of learning or practice, and less than half an hour after the bird had first seen the light of day.*
All adjustment of the senseorgans, in looking, listening, exploring by touch, and the like, must vary according to the varying position, distance, and shape of the object. Similarly, the act of darting upon a moving prey and seizing with beak or claw or mouth involves precise and delicate adaptation of movement to varying space relations. Think of swallows catching flies, and similar instances.
* Op. eit., pp. 3839.
The same kind of purely perceptual adaptation is often found in human beings. In boxing, in fencing, and similar activities, rapid adaptation to constantly varying conditions is required, adaptation which involves perceptual attention, so that eye and hand may keep pace, but which would frequently be hindered, rather than helped, by mental imagery. Or take the simple act of leaping from point to point. A man with the avenger of blood behind him may have to jump from crag to crag to save his life. His eye measures the distance to be crossed, and his muscles are adjusted accordingly so as to land him in a certain spot. If he stopped to mentally picture himself moving through the air over a certain space, he would in all probability perish. He must trust to his eye.
Perhaps the most striking instances of adaptation to varying conditions determined purely by congenital endowment, independent of prior experience, are to be found in the behaviour of ants.* All the activities characteristic of ants, as well as of bees and wasps, are in their main outline instinctive. They are displayed by ants which have been taken from their nest immediately after being hatched, and set apart to form a new nest. Independently of prior experience, the processes of nestbuilding, the rearing of the young, the capture of the socalled slaves, the maintenance of domestic animals, and the like, vary in adaptation to varying circumstances. The mode of building the nest varies with the situation and accessible material. Change in the weather causes them to make corresponding changes in their nest. When the nest is too damp, they pierce holes in it so that it looks like a sponge. This facilitates evaporation and keeps their home drier. In the tending of their young they show a similar plasticity. The youngest larvae are generally kept in the deepest chambers of the nest: the halfgrown in those above, and the fullygrown, together with the pupae, in the highest. When the weather is cold and rainy, they carry the more mature larvae from the higher into the lower chambers. The evidence seems to show that these and similar adaptations to varying circumstances are not learnt by experience, but are due to original plasticity of congenital endowment.*
* These adaptations are not free in the same degree as those described in the preceding paragraph. They are relative to comparatively fixed and specific circumstances.
* See Vergleichende Studien uber das Seelenleben der Ameisen und der hohern Thiere. Von E. Wasmann S.J. Freiburg: Herdersche Verlagshandlung, 1897. Pp. 122. Price, Is. 9d.