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 watching 
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 
