472 'Journal of Comparative Neurology and Psychology. 



In the light of these prehminary results we were able to plan a 

 more exact and thoroughgoing examination of the relation of 

 strength of stimulus to rapidity of learning. Inasmuch as the 

 training under the conditions of set I required a great deal of time, 

 we decided to shorten the necessary period of training by making 

 the two electric boxes very different in brightness, and the dis- 

 crimination correspondingly easy. This we did, as has already 

 been explained, by decreasing the amountof light which entered the 

 black box, while leaving the white box about the same. The influ- 

 ence of this change on the time of learning was very marked indeed. 



With each of the five strengths of stimuli which were used in 

 set II two pairs of mice were trained, as in the case of set I. The 

 detailed results of these five groups of experiments are presented 

 in tables 6 to lo. Casual examination of these tables reveals the 

 fact that in general the rapidity of learning in this set of experi- 

 ments increased as the strength of the stimulus increased. The 

 weakest stimulus (135 units) gave the slowest rate of learning; the 

 strongest stimulus (420 units), the most rapid. 



TABLE 6. 

 The results of the experiments of set II, stimulus 135 units. 



