286 Animal Intelligence 
Indeed it may be that this very reason,self-consciousuess 
and self-control which seem to sever human intellect so 
sharply from that of all other animals are really but second- 
ary results of the tremendous increase in the number, deli- 
cacy and complexity of associations which the human ani- 
mal can form.' It may be that the evolution of intellect 
has no breaks, that its progress is continuous from its 
first appearance to its present condition in adult civilized 
human beings.| | If we could prove that what we call idea- 
tional life and reasoning were not new and unexplainable 
species of intellectual life but only the natural consequences 
of an increase in the number, delicacy, and complexity of. 
associations of the general animal sort, we should have 
made out an evolution of mind comparable to the evolu- 
tion of living forms. | | 
In 1890 William James wrote, ‘‘The more sincerely one 
seeks to trace the actual course of psychogenesis, the 
steps by which as a race we may have come by the peculiar 
mental attributes which we possess, the more clearly one 
perceives ‘the slowly gathering twilight close-in utter 
dark.’”? Can we perhaps prove him a false prophet? Let 
us first see if there be any evidence that makes it probable 
that in some way or another the mere extension of the 
animal type of intellect has produced the human sort. If 
we do, let us proceed to seek a possible account of how this 
might have happened, and finally to examine any evidence 
that shows this possible ‘how’ to have been the real way 
in which human reason has evolved. 
It has already been shown that in the animal kingdom 
there is, as we pass from the early vertebrates down to man, 
a progress in the evolution of the general associative process 
which practically equals animal intellect, that this progress 
continues as we pass from the monkeys to man. Such a 
