MENTAL LIFE OF MONKEYS AND APES 127 



terest centered in behavior, he did not discuss ideation, but 

 this does not prevent the comparison of his data with those of 

 the present report, and the agreement of his findings with my 

 own is obvious. 



My work contrasts sharply with that briefly mentioned above 

 in that I apphed systematically and over a period of several 

 months an experimental method suited to reveal problem solv- 

 ing ability. Previously, the so-called problem or puzzle-box 

 method had been used as a means of testing for the presence 

 of ideas. For this I substituted the multiple-choice method. 

 One of the chief advantages of this new method is the possi- 

 bility of obtaining curves of learning for the solution or attempted 

 solution of relational problems of varying difficultness. I am 

 confident that these curves of learning will prove far more 

 valuable than such data as are yielded by the puzzle-box method. 



The Pithecus monkeys, which I studied intensively, yielded 

 relatively abundant evidences of ideation, but with Thorndike 

 I must agree that of "free ideas" there is scanty evidence; or 

 rather, I should prefer to say, that although ideas seem to be 

 in play frequently, the}^ are rather concrete and definitely at- 

 tached than " free." Neither in my sustained multiple-choice 

 experiments nor from my supplementary tests did I obtain 

 convincing indications of reasoning. What Hobhouse has called 

 articulate ideas, I believe to appear infrequently in these ani- 

 mals. But on the whole, I believe that the general conclusions 

 of previous experimental observers have done no injustice to 

 the ideational ability of monkeys. It is clearly important, how- 

 ever, that we always should take into account the species of 

 animal observed, for unquestionably there are extreme differ- 

 ences in mental development among the monkeys. 



As I view my results in the light of their relations to earlier 

 work, I am strongly impressed with the importance of the use 

 of improved methods for the study of complex behavior. The 

 delayed reaction method of Hunter, the quadruple-choice method 

 of Hamilton, and my multiple-choice method offer new and 

 promising approaches to forms of activity which thus far have 

 been only superficially observed. 



The ability exhibited by Skirrl to try a method out and then 

 to abandon it suddenly is characteristic of animals high in 

 intelHgence. Most of the problems which I presented to my 



