48 

 relatively easy or trials are given at greater intervals, 



as is indicated by Curve II, there is little of the irreg- 

 ular and steeple-like character to the curves; the descent 

 of the curves is rapid. On the other hand, when the prob- 

 lem is difficult or several trials were given, the curves 

 are more complex and irregular. There is some difficulty 

 in forming early organized movements. 

 RETENTION. 

 Very little has been said regarding the retention 

 characteristics of the rats. No definite conclusions 

 have been reached in regard to the distribution and the 

 number of trials on retention, for the results do not in-- 

 dicate whether retention is better after one, three or 

 five trials when one problem was offered. In some cases 

 one trial showed the best retention, and again three or 

 five proved more effective. This might be accounted for 

 by individual differences in the power of retention. The 

 same doubt esists when three problems were given abreast, 



