A GOOD test of the intelligence of any animal is its ability to learn to do a thing by being shown it or by being put through the requisite movements. Human adults would learn readily in either of these ways, because we thus get ideas of what to do and how to do it and modify our actions in accordance with these ideas. If the reader had never seen a glass or a faucet, he would nevertheless learn how to get a drink by turning a faucet and holding the glass beneath it, if he saw some one else do it, or if some one took his hands and put them through the movements. The intelligence required in such cases is not of a very advanced sort; it is not the power of abstract reasoning or of seeing the relationships of facts, but is simply the capacity to have ideas and to progress from the idea of doing a thing to the act itself.
A study which I made four years ago of the mental powers of dogs, cats and chicks showed that these animals did not, at least not habitually, learn from this sort of tuition. They learned only in the following manner: If in any situation their own impulses led them to do something which brought desirable results, they would, when put in that situation again, do that particular thing rather than anything else. If for instance a kitten was shut up in a box from which it could escape only by turning around a button which held the door, it would claw and bite and pull and squeeze at random as its instinctive impulses led it to do. If by chance it made a pull at the button and so secured freedom and food, it would, the next time it was put in that box, be likely to make that particular movement earlier than in its first trial. After enough trials it would pull the button around as soon as put into the box. It had learned by the selection of one of its own impulses. If you showed it how to get out by putting it in the box and turning the button for it, thus letting it out, it learned no more quickly than when by itself. So also if you took its paw and with it pulled the button round. And any acts which it failed to learn by means of the selection of chance successes from its own impulsive activities, it could never be taught by example or by being put through the movements, scores of times.
During 1900 I was engaged in investigating the mental capacities of monkeys and included in my experiments a number bearing upon this question. The monkeys are quicker to learn and learn more