take the phœbe that originally built its nest under ledges, and does so still to some extent. It, too, would find a more abundant food-supply in the vicinity of farm-buildings and bridges. The protected nesting-sites afforded by sheds and porches would likewise stimulate its nesting instincts, and it would react in the manner we see it every spring.
Nearly everything an animal does is the result of an inborn instinct acted upon by an outward stimulus. The margin wherein intelligent choice plays a part is very small. But it does at times play a part—perceptive intelligence, but not rational intelligence. The insects do many things that look like intelligence, yet how these things differ from human intelligence may be seen in the case of one of our solitary wasps—the mud- dauber,—which sometimes builds its cell with great labor, then seals it up without laying its egg and storing it with the accustomed spiders. Intelligence never makes that kind of a mistake, but instinct does. Instinct acts more in the invariable way of a machine. Certain of the solitary wasps bring their game—spider, or bug, or grasshopper— and place it just at the entrance of their hole, and then go in their den apparently to see that all is right before they carry it in.
Fabre, the French naturalist, experimented with one of these wasps, as follows: While the wasp was in its den he moved its grasshopper a few inches away. The wasp came out, brought it to the opening as before, and went within a second time; again the game was removed, again the wasp came out and brought it back and entered her nest as before. This little comedy was repeated over and over; each time the wasp must enter her hole before dragging in the grasshopper. She was like a machine that would work that way and no other. Step must follow step in just such order. Any interruption of the regular method and she must begin over again. This is instinct, and the incident shows how widely it differs from conscious intelligence. Or if you have a tame chipmunk, turn him loose in an empty room and give him some nuts. Finding no place to hide them, the chances are that he will carry them into one corner and pretend to cover them up. You will see his paws move quickly about them for an instant as if in the act of pulling leaves or mould over them. His machine, too, must work in that way. After the nuts have been laid down, the next thing in order is to cover them, and he makes the motions all in due form. Intelligence would have omitted this useless act.
Animals have keen perceptions—keener in many respects than our own,—but they form no conceptions, have no powers of comparing one thing with another. They live entirely in and through their senses. To all that inner world of reflection, imagination, comparison, reason, they are strangers. They never return upon themselves in thought. They have sense memory, sense intelligence, and they profit in many ways by experience, but they have not soul memory, or rational intelligence. All the fundamental emotions and appetites men and the lower animals share in common, such as fear, anger, love, hunger, jealousy, cunning, pride, curiosity, play, but the world of thought and thought experience, and the emotions that go with it, belongs to man alone.
It is as if the psychic world were divided into two planes, one above the other—the plane of sense and the plane of spirit. In the plane of sense live the lower animals, only now and then just breaking for a moment into the higher plane. In the world of sense man is immersed also; this is his start and foundation; but he rises into the plane of spirit, and here lives his proper life. He is emancipated from sense in a way that beasts are not.
Thus, I think, the line between animal and human psychology may be pretty clearly drawn. It is not a dead-level line. Instinct is undoubtedly often modified by intelligence, and intelligence is as often guided or prompted by instinct, but one need not hesitate long as to which side of the line any given act of man or beast belongs. When the fox resorts to various tricks to outwit and delay the hound (if he ever consciously does so), he exercises a kind of intelligence—the lower form which we call cunning,—and he is prompted to this by an instinct of self-preservation. When the birds set up a hue and
