DELAYED REACTION 35 



B. Maximal Intervals of Delay Attained, (a) Group differ- 

 ences as to maximal delay. — The only conditions of experimen- 

 tation that varied from animal group to animal group were 

 these: (i) Number of trials daily. Rats 2, 4, 5, 6, 7 and 9 

 (Set A) and rats 10, 11 ,14 and 17 (of Set B) were given 5 trials 

 daily. Rats 12, 13, 15 and 16 (of Set B) received 10 trials. 

 The two dogs were given 10 trials daily. Of the raccoons, Jack 

 and Jill were each given 15 trials and Bob and Betty 10 trials 

 daily. (2) The rats of Set B were tested with reward alone. 

 As was mentioned above, the dogs and raccoons were very 

 much discomfited by having to back out of the light boxes 

 when a wrong choice had been made. This was even more 

 true in our tests than in most discrimination work owing to 

 the small size of the light boxes. 



TABLE IV 



Per cent of 

 Rat Maximal delay correct response 



Set A tested with reward. 

 Set B tested with reward and punishment. 



Those rats that are marked with a * received 10 trials daily. All the others re- 

 ceived 5. 



Table IV gives the maximal delay attained by the rats. The 

 percentages are computed on a basis of 25 trials. It will be 

 seen from this that only four rats of the fourteen tested reached 

 intervals greater than one second. The percentage of correct 

 behavior for one of these (No. 7) was only 56. Rats Nos. 4, 

 II, 15, 16 and 17 were tested with a choice of two boxes as 

 opposed to three. This was done only after the animals had 



