98 



JOSEPH U. YARBROUGH 



trials showed much improvement, 29 of them being correct 

 reactions. Although Bobby had 30 more trials on this delay 

 than Jim, she made only 26 out of her last 30 trials. This is 

 readily explained in the light of the fact that the middle com- 

 partment was dropped out during this period with Jim, while 

 Bobby continued on three compartments. Jim had made 70% 

 on the last 40 trials preceding the 30 trials mentioned above, of 

 which he got 29 correct. At the end of these 40 trials, the middle 

 compartment was dropped out. Of the first 10 trials with only 

 two compartments, Jim made 100% correct. The records show 

 that Jim would have made a higher percentage than 70 much 

 sooner had it not been for a tendency to drop out the middle 

 box. This is not only seen in table IV, but by the fact that 

 when he received the stimulus only from boxes "a" and "c" 

 (the experimenter having dropped out the middle box), he made 

 100% on the first 10 trials. 



TABLE IV 

 Daily Record on 4 Seconds Delay with Light 



