MENTAL LIFE OF MONKEYS AND APES 125 



Romanes (1900), Morgan (1906), Washburn (1908), and Holmes 



(1911). 



Evidences of Ideation in Monkeys 



Aside from anecdotal and traveller's notes on the behavior 

 of monkeys and apes we have only a scanty literature. In 

 fact, the really excellent articles on the behavior and mental 

 life of these animals may be counted on one's fingers; and not 

 more than half of these are experimental studies. I shall, in 

 this brief historical sketch, neglect entirely the anecdotal litera- 

 ture, since my own work is primarily experimental, and since 

 its results should naturally be compared with those of other 

 experimenters. 



Thorndike (1901), the American pioneer in the application of 

 the experimental method to the study of mind in animals, pub- 

 lished the first notable paper on the psychology of monkeys. 

 His results force the conclusion that "free ideas" seldom appear 

 in the monkey mind and have a relatively small part in beha- 

 vior. That the species of Cebus which he observed exhibits 

 various form.s of ideation he is willing to admit. But he insists 

 that it is of surprisingly little importance in comparison with 

 what the general behavior of monkeys as known in captivity 

 and as described by the anecdotal writers have led us to expect. 

 It is important to note, however, that Thorndike' s observations 

 were limited to Cebus monkeys which, as contrasted with various 

 old world types, are now considered of relatively low intelligence. 



In many respects the most thoroughgoing and workmanlike 

 experimental study of monkeys is that of Kinnaman (1902), 

 who has reported on the study of various forms of response 

 in P. rhesus. He presents valuable data concerning the learn- 

 ing processes, sensory discrimination, reaction to number, and 

 to tests of imitation. His results indicate a higher level of 

 intelligence than that discovered by Thorndike, but this is 

 almost certainty due to difference in the species observed. Kin- 

 naman goes so far as to say "We have found evidence, also, 

 of general notions and reasoning, both of low order " (p. 211). 



The contribution of Hobhouse (1915) to our knowledge of the 

 mental life of monkeys, although in a measure experimental, is 

 based upon relatively few and unsystematic observations as 

 contrasted with those of Thorndike and Kinnaman. It ap- 

 pears, however, that Hobhouse's experiments were admirably 



