258 Journal of Comparative Neurology and Psychology. 



experiments. Had the tests been made with a condition of greater 

 difference in the illumination of the two boxes the results probably 

 would have indicated a slight increase in plasticity with age, instead 

 of a decrease. If then under one condition of training plasticity 

 diminishes as the dancer grows older, and under another condition 

 in connection with the same habit it increases, it is clear that the 



TABLE 10. 



Relation of Age to Rapidity of Habit-formation Under Conditions of Easy 



AND OF Difficult Discrimination. White-black Discrimination. 



Discrimination at first easy and later difficult. 



*At this point condition of discrimination was changed from "easy" to "diflBcult." 



relation of age to rapidity of habit-fonnation is more complex than 

 certain statements made by students of animal behavior would lead 

 one ±0 suppose. 



M}^ experiments reveal the presence and importance of a number 

 of variable factors in the white-black discrimination habit; and 

 until we know accurately the values and relations of these several 



