38 



Group XVI 



Animal Trials 



No. 62 540 



No. 66 495 



No. 72 285 



No. 74 405 



No. 75 ,450 



No. 76 450 



Average ^37.5 



29.16 



Group XIX 



Animal Trials Series 



No. 152 705 47 



No. 153 630 42 



No. 154 645 43 



No. 155 630 42 



No. 156 705 47 



Average 663 44.2 



Average for 27 animals, 525.5 trials, 35.03 series. 



The record for Group XVII is not included in the average 

 with the remaining groups since we were compelled to make 

 some changes in the method of procedure with that group. 

 It was the first group to which we attempted to teach the 

 negative response to sound and by means of it a final method 

 was worked out. We gave the seven members of this group 

 on the average fifty series of trials with the same sort of 

 series as was used in the positive response previously re- 

 ported and with the single sounder located in the food box 

 and marked S in figure II. After the complete failure of all 

 seven animals to show any evidences of learning in the fifty 

 series of twenty trials each except such as could be ascribed 

 to position habits, the three sounders along each side of the 

 experiment box were introduced and the type of series 

 adopted which was used in all the experiments with the 

 negative response. After these changes were made the 

 record for this group in learning the sound is practically 

 the same as the normal record for sound secured later 

 with the other groups reported. 



To bring out the main features of the learning process 

 when the sound was used, I have inserted a few typical 

 curves. These curves show the same general features as 

 those illustrating the learning with the light. In these 

 curves, however, some of the distinctive features show up 



