46 HARRY H. WYLIE 



relapses nor plateaus, the process of learning the negative 

 response to the electric shock in these experiments repre- 

 sents practically an ideal case. 



There is no striking difference in the lengths of the non- 

 learning periods for the pain and for the light. Neither is 

 there any important difference in the number of series 

 necessary to complete the learning process with the pain 

 and with the light. The only really significant difference 

 is in the smoothness of the rise of the curve in each case, 

 yet this difference is not so great as to be very striking. It 

 is likely due, as suggested above, to the greater power of 

 compelling attention which the electric shock seems to 

 possess. Its unlikeness, measured from the human stand- 

 point, to anything else falling within the normal experi- 

 ence of the white rat might be the secret of its power. 



But we still have the question of why the light was prac- 

 tically just as effective as the electric shock while the sound 

 was decidedly less effective, having both a much longer 

 non-learning period, a much greater irregularity of effec- 

 tiveness, and a much longer learning period. Why this 

 advantage of light over sound if the animals are really 

 negative to neither? As suggested above, the animals 

 seemed more inclined to be negative to the sound than to 

 the light, if we are to judge from the general disturbance 

 in their behavior produced by the two. If this were true, 

 one would expect the response to the sound to be learned 

 more quickly than to the light. Just the opposite was the 

 case. Moreover, the animals were evidently negative to 

 the electric shock but not to the light. Yet they learned 

 the response to the light in practically the same way and 

 practically as quickly as to the electric shock. But it might 

 be that the greater emotional disturbance caused by the 

 electric shock offset its greater effectiveness due to the 

 animal's being negative to it. Perhaps the explanation of 

 the comparative effectiveness of the light and sound can 

 be found partly in the general conditions under which the 

 experiments were conducted. It was much easier to control 

 the light from external sources than the sound. So the 

 light when presented represented a more uniform contrast 

 with the general environment than the sound when it was 



