The Mental Life of the Monkeys 175 
rarely or never learns in this fashion.. The present study 
of the primates has been a comparative study with two 
main questions in view: (1) How do the monkeys vary 
from the other mammals in the general mental functions 
revealed by their methods of learning? (2) How do they, 
on the other hand, vary from adult civilized human beings? 
The experiments to be described seem, however, to be of 
value apart from the possibility of settling crucial questions 
by means of the evidence they give. To obtain exact 
accounts of what animals can learn by their own unaided 
efforts, by the example of their fellows or by the tuition 
of a trainer, and of how and how fast they learn in each 
case, seems highly desirable. I shall present the results 
in the manner which fits their consideration as arguments 
for or against some general hypotheses, but the naturalist 
or psychologist lacking the genetic interest may find an 
interest in them at their face value. I shall confine myself 
mainly to questions concerning the method of learning of 
the primates, and will discuss their sense-powers and un- 
learned reactions or instincts only in so far as is necessary 
to its comprehension. 
It has been impossible for the author to make helpful 
use of the anecdotes and observations of naturalists and 
miscellaneous writers concerning monkey intelligence. 
The objections to such data pointed out in Chapter II, 
pp. 22-26, hold here. Moreover it is not practicable 
to sift out the true from the false or to interpret these 
random instances of animal behavior even if assuredly true. 
In the study of animal life the part is only clear in the 
light of ‘the whole, and it is wiser to limit conclusions to 
such as are drawn from the constant and systematic study 
of a number of animals during a fairly long time. After 
_a large enough body of such evidence has been accumulated 
we may be able to interpret random observations. 
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