The Mental Life of the Monkeys 223 



the movement. An adult human being whose hand was 

 taken and made to push in a bar or pull back a bolt would 

 thereby learn to do it for himself. Cats and dogs would 

 not, and the monkeys are not proved to do so. On the 

 other hand, it is impossible for me to say, as of the dogs and 

 cats, that the monkeys are proved not to do so. In a few 

 cases the animals did perform acts after having been put 

 through them which they had failed to perform when left 

 to their own trial and success method. In the majority of 

 cases they did not. And in some of these latter cases fail- 

 ure seemed so improbable in case the animal really had the 

 power of getting an idea of the act and proceeding from idea 

 to execution, that one is inevitably led to some explanation 

 for the few successes other than the presence of ' ideas.' 



The general manner of making these experiments was like 

 that in the case of the cats and dogs, save that the monkey's 

 paw was used to open the box from the outside instead of 

 from the inside, and that the monkeys were also put through 

 the acts necessary to operate some of the chute mechanisms. 

 Tests parallel to that of comparing the behavior of kittens 

 who had themselves gone into boxes with those who were 

 dropped in by me were made in the following manner. I 

 would carry a monkey from his cage and put him in some 

 conspicuous place (e.g. on the top of a chair) and then give 

 him a bit of food. This I would repeat a number of times. 

 Then I would turn him loose in the room to see whether he 

 had acquired an idea of being on the chair which would lead 

 him to himself go to the chair. I would, in order to tell 

 whether his act, in case he did so, was the result of random 

 activities or was really due to his tuition, leave him alone for 

 5 or 10 minutes before the tuition. If he got on the chair 

 afterwards when he had not before, or got on it much 

 sooner, it would tend to show that the idea of getting food 



