104 JOSEPH U. YARBROUGH 



eight seconds. Jim was given 30 trials with this period of 

 delay 27 of which were correct. As he appeared to meet no 

 difficulty in bridging this period, he was set to work on ten seconds 

 delay where he reacted 28 times correctly in 30 trials. On 

 twelve seconds delay he made 90% on 30 trials. Since he had 

 so successfully bridged over these small advances in delays, the 

 next increase was double in length, i.e., four seconds. Forty 

 trials were given with a delay of sixteen seconds. The problem 

 did not seem to increase in difficulty for 36 of these 40 presenta- 

 tions were reacted to correctly. 



The longest period of delay in which a regular series of experi- 

 ments were offered was eighteen seconds. One hundred tests 

 were given Jim on this period of delay, and of this number he 

 responded correctly to 91. During these experiments, Jim was 

 observed as closely as possible as to the orientation of head and 

 body when the door of the release box went up, and also at the 

 moment he initiated the movement of response. The matter 

 of orientation will be taken up again under the discussion of 

 " behavior during delay." 



(b) Cats tested on sound. — Bess and Phil had been dropped 

 back to the two seconds delay before the middle box was dropped 

 out. Beginning with the two seconds delay they were promoted 

 simultaneously from one interval of delay to another. 



Figured on the basis of 30 trials, Bess' percentage jumped 

 from 66 to 95, and Phil's from 80 to 96. On the four seconds 

 delay no difficulty was met. After 40 trials, — Bess with 93% 

 and Phil with 99, — they were promoted to the six seconds delay. 

 Here they received 40 trials, Bess making 95%, while Phil made 

 only 77%. This low percentage on the part of Phil was caused 

 by a pronounced position habit which appeared on the first day 

 and lasted through the second day of the series. They each 

 received 30 trials on both the eight and the ten seconds delays, 

 and each held a percentage of about 85. Since these periods 

 were bridged so easily, the period of delay was now lengthened 

 to fourteen seconds. On this interval of delay, 40 trials were 

 given, and Bess held 87%, while Phil made 98%. Ninety trials 

 were made by each cat on the sixteen seconds delay. Of these 

 90 trials, Bess was successful 84 times, and Phil 81 times. Dur- 

 ing this last period of delay of 90 trials, special observation was 

 made of orientation. These observations were recorded in detail, 



