STIMULI DURING DELAYED REACTION IN DOGS 263 



delay period. Release box turned 90 degrees during delay 

 period. Food given after correct reaction. 



In the early experiments the order of trials was prearranged, 

 and followed strictly during the trials. However, in the later 

 trials a given experiment was repeated as many times as necessary 

 to secure a successful reaction. Otherwise the prearranged order 

 was followed out. Care was taken that the order of trials 

 should not be such that a possible rhythm could be followed. 

 Record of attention to the stimulus was noted by means of 

 watching the dog through the glass top of the release box. 



Any particular orientation during the delay period was watched 

 for and noted. The path to the food compartment was re- 

 corded and hesitations or wide turns were especially noted. 



The designation " Two Light," " Three Light "and " Four 

 Light " experiments refer to those experiments in which the 

 stimulus was given in one of the possible two, three or four 

 compartments and the dogs were forced to discriminate the 

 correct one of these several possibilities. 



In the early experiments the trials were given in series of 

 five and ten, and no advance was allowed until 50% of a series 

 were correct reactions. Beginning with the ' Two Light " 

 experiments, and continuing through the rest of the work, no 

 advance was made until at least five successive correct reactions 

 were obtained. 



At first the dog was called back to the release box after a 

 trial, if he did not return at once of his own accord. It was 

 noticed, however, that after a number of unsuccessful trials, 

 the dog would refuse to leave the release box on the opening 

 of the door. The dog at the beginning of the ( ' Two Light ' 

 experiments returned so regularly that it was decided not to 

 call him back anymore. After this change the dog would lie 

 down for a minute or two, if discouraged by several unsuccessful 

 trials, and then would return to the box with renewed energy 

 and with his attention to the problem as keen as ever. He did 

 not refuse to leave the release box any more after this change in 

 the method was made. 



The time of the day when the trials were made varied from 

 8 to 11:30 A. M. As an interesting sidelight it may be noted 

 that the time from 10 to 11:30 A. M. was the period in which 

 the dog was the most attentive and eager, hence giving the 



