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 II 

 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. 



