The Mental Life of the Monkeys r73 
INTRODUCTION 
The work to be described in this paper is a direct contin- 
uation of the work done by the author in 1897-1898 and 
described in{ Monograph Supplement No. 8 of the Psycho- 
logical Review under the heading, ‘Animal Intelligence; 
an Experimental Study of the Associative Processes in 
Animals.’! This (monograph affords by far the best in- 
troduction to the present discussion,/and I shall therefore 
assume an acquaintance with it on the part of my readers. 
It will be remembered that evidence was there given that 
ordinary mammals, barring the primates, did not infer or 
compare, did not imitate in the sense of ‘learning to do an 
act from seeing it done,’ did not learn various simple acts 
from being put through them, showed no signs of having in 
connection with the bulk of their performances any mental 
images. | Their method of learning seemed to be the grad- 
ual selection of certain acts in certain situations by reason 
of the satisfaction they brought. Quantitative estimates 
of this gradualness were given for a number of dogs and 
cats. Nothing has appeared since the ‘Experimental Study’ 
to negate any of these conclusions in the author’s mind. 
The work of Kline and Small? on rodents shows the same 
general aspect of mammalian mentality. 
dult human beings who are not notably deficient in 
mental functions, at least all such as psychologists have 
observed, possess a large stock of images and memories. 
The sight of a chair, for example, may call up in their minds 
a picture of the person who usually sits in it, or the sound 
of his name. The sound of a bell may call up the idea of 
1 Pp. 20 to 155 of this volume. 
2 American Journal of Psychology, Vol. X, pp. 256-279; Vol. XI, pp. 80- 
100, 131-165; Vol. XII, pp. 206-239. 
