274 MENTAL LIFE OF APES AND MONKEYS 



ments gave negative results and many others leave us in 

 doubt as to the interpretation of the behavior described, 

 there are some in which the evidence points strongly to- 

 ward imitation. The monkeys were put in cages in which 

 there were mechanical devices by operating which they 

 could procure food. Each monkey was given five trials of 

 fifteen minutes each on successive days. If he did not 

 secure food by his unaided efforts he was allowed to see 

 another monkey operate the device and was then allowed 

 to try again. The lessons were kept up until 100 tests were 

 made before the monkey was dismissed as a hopeless failure. 

 In many cases monkeys which failed to operate the devices 

 alone did so after watching other monkeys work them one or 

 more times. The attention of the monkeys was usually 

 stimulated when they saw other monkeys obtain food by 

 working the devices. Very frequently the imitation was 

 not perfect at first, but the various features of the trick 

 were learned one after the other. 



There is a possible doubt relative to the interpretation of 

 Mr. Haggerty's experiments. Since the monkey which 

 served as a model learned the trick to be copied it is possible 

 that the monkey which performed the trick after \vatching 

 him may have learned it at first hand also. The case for 

 imitation can be made out only by the accumulation of a 

 sufficient number of instances to rule out coincidences and 

 accidents. How far Mr. Haggerty has made out his case 

 can be judged only by a careful study of the details given 

 in his paper. 



Whether apes and monkeys reason is a question whose 

 answer depends on the sense in which the term reason is 

 employed. If we define reason as the derivation of conclu- 

 sions through the comparison of concepts it is not improbable 

 that no animal below man employs this faculty. But this 



