482 'Journal of Comparative Neurology and Psychology. 



demand difficult sense discriminations or complex associations, 

 may readily be formed under strong stimulation, whereas a diffi- 

 cult habit may be acquired readily only under relatively weak 

 stimulation. That this fact is of great importance to students of 

 animal behavior and animal psychology is obvious. 



Attention should be called to the fact that since only three 

 strengths of stimulus were used for the experiments of set I, it is 

 possible that the most favorable strength of stimulation was not 

 discovered. We freely admit this possibility, and we furthermore 

 wish to emphasize the fact that our fifth conclusion is weakened 

 slightly by this uncertainty. But it is only fair to add that pre- 

 vious experience with many conditions of discrimination and of 

 stimulation, in connection with which more than two hundred 

 dancers were trained, together with the results of comparison of 

 this set of experiments with the other two sets, convinces us that 

 the dancers would not be likely to learn much more rapidly under 

 any other condition of stimulation than they did with a strength 

 of 300 ± 25 units of stimulation. 



Naturally we do not propose to rest the conclusions which have 

 just been formulated upon our study of the mouse alone. We 

 shall now repeat our experiments, in the light of the experience 

 which has been gained, with other animals. 



