62 BRAINS OF RATS AND MEN 



and similar conditioned responses to confirm both 

 the neurological outline and the general physiological 

 principles essentially as stated, though it must be 

 kept in mind that this statement is incomplete and 

 by no means covers all of the factors involved. 



The thalamus of lower vertebrates as a true 

 correlation center certainly can perform functions in 

 the simpler types of learning of the sort here illus- 

 trated, without cortical participation. This readjust- 

 ment of thalamic neural arcs is, however, a slow and 

 difficult process, and many repetitions are necessary. 

 Learning by trial-and-error is typical of this sort oi 

 education. 



In still more complicated learning processes the 

 co-operation of the cerebral cortex is known to be 

 necessary, and one of the major problems before us 

 is the exact part played here by the cortex. It is 

 clear that animals with large and very complex 

 cortical development (and man in particular) learn 

 more by personal experience and learn more rapidly. 

 Their learning curves may be radically different from 

 the usual trial-and-error curve. 



The lower vertebrates may, on occasion, acquire a 

 new mode of response after a single experience, but 

 more often the learning is a slow process involving 

 much random fumbling as overt behavior. The man 

 more readily reaches a correct solution of the problem 

 of conduct in an unfamiliar situation without random 

 overt trials, though the "trials" which do not come to 



