240 Animal Intelligence 
that the only demonstrable intellectual advance of the mon- 
keys over the mammals in general is the change from a few, 
narrowly confined, practical associations to a multitude of 
all sorts, for that may turn out to be at the bottom the 
only demonstrable advance of man, an advance which in|con- 
nection with a brain acting with increased delicacy and 
irritability, brings -in its train the functions which mark off 
human mental faculty from that of all other animals!!_! 
The typical process of association described in Chapter IT 
has since been found to exist among reptiles (by Mr. R. 
M. Yerkes) and among fishes (by myself). It seems fairly 
likely that not much more characterizes the primates. If 
such work as that of Lubbock and the Peckhams holds its 
own against the critical studies of Bethe, this same process 
exists in the insects. Yerkes and Bosworth think they 
have demonstrated its presence in the crayfish. Even if 
we regard the learning of the invertebrates as problematic, 
still this process is the most comprehensive and important 
thing in mental life. I have already hinted that we ought 
to turn our views of human psychology upside down and 
study what is now casually referred to in a chapter on habit 
or on the development of the will, as the general psycho- 
logical law, of which the commonly named_ processes are 
derivatives. When this is done, we shall not only relieve 
human mentality from its isolation and see its real rela- 
tionships with other forms; we may also come to know more 
about it, may even elevate our psychologies to the explana- 
tory level and connect mental processes with nervous activ- 
ities without arousing a sneer from the logician or a grin 
from the neurologist. 
