6 E. L. THORNDIKE. 



observation and the collection of anecdotes. Thus you immedi- 

 ately get rid of several of them. You can repeat the conditions 

 at will, so as to see whether or not the animal's behavior is due 

 to mere coincidence. A number of animals can be subjected to 

 the same test, so as to attain typical results. The animal may be 

 put in situations where its conduct is especially instructive. 

 After considerable preliminary observation of animals' behavior 

 under various conditions, I chose for m)^ general method one 

 which, simple as it is, possesses several other marked advantages 

 besides those which accompany experiment of any sort. It was 

 merely to put animals when hungry in enclosures from w^hich 

 they could escape by some simple act, such as pulling at a loop 

 of cord, pressing a lever, or stepping on a platform. (A de- 

 tailed description of these boxes and pens will be given later.) 

 The animal was put in the enclosure, food was left outside in 

 sight, and his actions observed. Besides recording his general 

 behavior, special notice was taken of how he succeeded in doing 

 the necessary act (in case he did succeed), and a record was 

 kept of the time that he was in the box before performing the 

 successful pull, or clawing, or bite. This was repeated until 

 the animal had formed a perfect association between the sense- 

 impression of the interior of that box and the impulse leading to 

 the successful movement. When the association was thus per- 

 fect, the time taken to escape was, of course, practically con 

 stant and very short. 



If, on the other hand, after a certain time the animal did not 

 succeed, he was taken out, but not fed. If, after a sufficient 

 number of trials, he failed to get out, the case was recorded as 

 one of complete failure. Enough different sorts of methods of 

 escape were tried to make it fairly sure that association in gene- 

 ral, not association of a particular sort of impulse, was being 

 studied. Enough animals were taken with each box or pen to 

 make it sure that the results were not due to individual peculiar- 

 ities. None of the animals used had any previous acquaintance 

 with any of the mechanical contrivances by which the doors 

 were opened. So far as possible the animals were kept in a 

 uniform state of hunger, which was practically utter hunger. 

 That IS, no cat or dog was experimented on when the experi- 



