33^ yournal of Comparative Neurology and Psychology. 



more, a monJiey lifting a latch is a very different stimulus for an 

 observing monkey from a person lifting the same latch. In view of 

 these considerations it is imj)ortant in an experimental study of 

 imitation in monkeys to deal separately with the two questions pro- 

 posed above. The first question, Do monkeys imitate human beings 'f 

 is only indirectly related to the natural activities of the animals ; 

 the second. Do they imitate one another ? is extremely important 

 for an understanding of the behavior and mental life of monkeys. 

 To discover in what w^ays certain sj^ecies of monkeys are influenced 

 by one another's acts has been the chief aim of the investigation 

 which I have here to report. 



2. History of Present Investigation. The investigation was be- 

 gun in the Harvard Psychological Laboratory in October, 1907. 

 From that time until June, 1908, the experimenter devoted himself 

 (a) to studying the behavior of three Cebus monkeys; (b) to making 

 experiments with these individuals for the purpose of developing 

 methods of testing imitative ability, and (c) to devising and con- 

 structing apparatus for experimental work. 



In June, 1908, the investigation was transferred to the Xew York 

 Zoological Park in order to make use of the large collection of mon- 

 keys available there. The apparatus which had been built in Cam- 

 bridge, and two of the Cebus monkeys which had been used in the 

 preliminary experiments were taken to the Park. Here, under 

 peculiarly favorable conditions the investigation was continued until 

 September. Well-prepared apparatus and methods of experimental 

 procedure, the fine collection of animals and the excellent local 

 conditions provided by those in charge of the Park, greatly facili- 

 tated the work and within the short space of ten weeks much was 

 accomplished in the way of results. 



3. The ^Vorh of Other Investigators. — I^oteworthy observations 

 concerning the imitative ability of monkeys have been made under 

 experimental conditions by Thorndike\ by Kinnaman^, by Hob- 



'Thorndike, Edward L. The Mental Life of the Monkeys. Psycholoffical 

 Review, Monograph Supplement, vol. 3, no. 5, 57 pp. 1901. 



=KiNNAMAN, A. J. Mental Life of Two Macacus Rhesus Monkeys in Cap- 

 tivity. American Journal of Psyclioloyy, vol. 13, pp. 98-148; 173-218. 3902. 



