TRANSFER OF RESPONSE IN THE WHITE RAT 39 



much more plainly than in those for the light stimulus. 

 These curves show the complete record for the animals, 

 both while learning the sound and when transferred to the 

 light and pain. Figures XIV to XVII. 



The significant features of the learning process with the 

 negative response to the sound stand out most clearly in 

 the individual curves presented. These features have 

 already been mentioned — the rather long period of no pro- 

 gress at first, the sudden and rapid perfecting of the response 

 when once learning begins, and the few errors after once the 

 response is learned. An apparent exception is the record 

 of number 61 of group XIV. Here the early part of the 

 record is very irregular until the eighteenth series, when 

 it rises regularly and rapidly to perfection at the twenty- 

 fifth series. In contrast with this record stands that of 

 number 67 of Group XV. No sign of learning was shown 

 there until the thirteenth series and learning was prac- 

 tically complete in the twenty-first series. Or still more 

 striking is the contrast shown by the record for number 

 154 of Group XIX. While there is some slight evidence 

 from " hesitations " that the sound stimulus was being 

 noticed from the very first, not until the thirty-fifth series 

 did good evidence of learning appear, and learning was 

 practically complete by the thirty-eighth series. The 

 record for number 129 of Group XVIII shows the most 

 gradual rise of any, although for seventeen series, there is 

 scarcely any sign of learning. For this rat it took thirty-one 

 series to complete the learning after it began to exhibit pro- 

 gress whereas the usual number with the sound is much 

 less, one even falling as low as four. It is the only case 

 where the learning can be truly spoken of as a gradual 

 process. 



(3) Pain, — Seven groups of animals, XX-XXVI in- 

 clusive, were taught the negative response to pain. All of 

 these represent normal records except Group XXII. Its 

 record, therefore, has been omitted. This group was the 

 first to be trained with the pain stimulus and served in 

 part to work out the particular method for giving the pain 

 stimulus. At first the stimulus was given at one point 

 only as the animal came down the alley, the point being 



