196 



BRAINS OF RATS AND MEN 



B 



Fig. 49. — Simplified schemata of the situation at three successive 

 stages of the latch-box experiment. 



I. Before training. The "natural" reflex, upon presentation of the 

 food stimulus (S), involves transmission of a nervous impulse to the corre- 

 lation center (C), as a result of which the rat makes the reaction (F) which 

 takes It directly to the food in the open box (B). 



II. During early training. The "natural" response to the food (F) 

 Is blocked by closure of the door of the food-box (B). Summation and 

 overflow of excitations in the correlation center (C) result in various 

 exploratory and random movements. 



III. Completed training. The initial response Is transferred from 

 the food (F) to the latch (L), as indicated by the line C'-L. When con- 

 tact with the latch is reported back to the center, as indicated by the 

 line L-C"y this second stimulus evokes the original response, as indi- 

 cated by the line C"-F, and the reaction is consummated. 



