RATE OF LEARNING IN THE WHITE RAT 27 



See data in Table X and the learning curve in Fig. 6. The prob- 

 lem for Group X differed from that for Group IV only in the 

 matter of stimuli used, but there is a marked difference between 



TABLE X 



Animal Trials 



13 160 



16 180 



19 160 



35 180 



Average 170 



the curves for the two groups. In the Group IV curve is shown 

 a period of no learning, followed by a brief plateau and a second 

 period of gradual growth, which brings the record up to the 

 standard. In contrast, the Group X curve shows a shorter period 

 of no learning, followed by rapid progress. There are two pos- 

 sible explanations for this dissimilarity. First, it may be due 

 to the previous training the animals in Group X had had in the 

 problem of pain-sound transfer. Second, the pain-sound trans- 

 fer may be more difficult than the sound-light transfer. 



4) Four-second Interval. The animals in Group XI were 

 trained to associate light with the buzzer when presented with 

 a time interval of four seconds. Table XI records the results. 



TABLE XI 



Animal Trials 



4 160 



23 140 



38 160 



39 160 



Average 155 91.5 



From these data and the curve in Fig. 7 one may see the rate 

 of learning the association and the number of trials necessary 

 to master the problem. There are no marked differences between 

 the data of this group and those of Group X above. In each 

 case there is a complete breakdown in the early part of the period 

 followed by a period of rapid learning. With this group there 



