THE INTELLIGENCE OF MONKEYS. 273 



THE INTELLIGENCE OF MONKEYS. 



By professor EDWARD L. THORNDIKE, 



TEACHERS COLLEGE, COLUMBIA UNIVERSITY. 



AGOOD 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 habitu- 

 ally, learn from this sort of tuition. They learned only in the following 

 manner: If in any situation their own impulses led them to do some- 

 thing 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 free- 

 dom 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 



VOL. LIX. — 18 



