354 THE INTERMEDIATE PRIMATES 



learning process, sensory discrimination, number reaction and tests of imita- 

 tion. The results indicate a considerably iiigher level of intelligence tiian 

 that ascribed by Thorndyke to the new-world monkeys which he subjected 

 to such tests. Kinnaman found evidence also of general ideas and reasoning, 

 both of which, however, are of a k)w order. Hobhouse (1915) in a further 

 contribution to our knowledge of the mental Hfe of monkeys, in tests that 

 were admirably adapted to gauge the ideational capacity of these subjects, 

 agrees in general with Kinnaman that the macacus monkey is possessed of 

 definite ideas. 



In 1908 J. B. Watson, testing the imitative ability of Macacus rhesus, 

 found relatively little evidence of other than extremely simple forms of 

 ideation. On the other hand, Haggerty (iQOt)), after much more extended 

 investigation of several species of this family, obtained convincing evidence of 

 ideation and imitative behavior, and concluded that these simian forms 

 depended upon a certain degree of ideational experience. Witmer (1910), in 

 confirmation of Haggerty's results, reports definitely imitative beliavior in 

 Pithecus irus; while the work of Shepherd ( 1910) agrees closely, so far as the 

 evidence of ideation is concerned, with Thorndyke. The species employed in 

 his tests was Macacus rhesus; all of which, he iDelieved, exhibited ideas of a low 

 order or something closely corresponding to ideas. Franz (1907-1911), in 

 consequence of his study upon these monkeys, was able to throw no special 

 light upon the problem of ideation, although his mode of approach took into 

 account rather the function of various portions of the brain than the accurate 

 description of various features of behavior. In 191 1, Hamilton, investigat- 

 ing both Macacus rhesus and Macacus irus, employed an ingenious quad- 

 ruple choice method which showed that the two monkeys exhibited a fairly 

 adequate type of ideational response. 



Yerkes, in his extensive monograph, "The Mental Life of Monkeys 

 and Apes" (1916), was able to disclose results which contrast rather sharply 



