8 JOHN LINCK ULRICH 



Plate I. Both the number of trials and the number of days 

 required are shown by squares arranged on base Hnes. Males 

 are indicated by plain squares, and females by squares with a 

 diagonal. The squares on the base lines on the lower half of 

 the plate show the number of trials given each individual . rat 

 in the one, three and five trial groups. The upper half of the 

 plate shows the number of days required, and their distribution. 

 The rats which required a norm higher than one second are 

 indicated by a circle in the squares. 



n 3a Fm 



PLATE I 



DISTRIBUTION CURVE 

 I \ M I LATCH BOK 



I-1//1 I I I . 



BY TRIALS 



D MALES 

 U FEMA1.C5 



HggR^ 



la zo u 



a a H 



X] □_ 



B H 



On a close examination of this plate, it is seen that a group 

 of rats given one trial daily learned the problem with fewer 

 trials than those given three or five trials. This is shown best 

 by noting in how many trials the first rat in each of the groups 

 completed the task. The first rat in the one trial group learned 

 the problem in 11 trials, in the three and five trial groups in 

 21 and 30 trials respectively. A like comparison can be made 

 of the three groups with rats that required the greatest number 

 of trials. These results show that learning is most economical 

 (number of trials) when one trial is demanded of a rat. But, 

 when considering the number of days demanded for the prob- 



