RATE OF LEARNING IN THE WHITE RAT 31 



viously learned negative response from pain over to the auditory 

 stimulus (electric buzzer). The buzzer was given in each case 

 after the pain had been given : to Group XIII it was presented 

 in immediate succession; to Group XIV, with an interval of one 

 second separating it from pain. Thus, in the latter case the two 

 factors were presented in the backward order with a time inter- 

 val of one second between them, i.e., the sound stimulus was pre- 

 sented after the motor response to pain had been initiated and in 

 some cases completed. All the animals were given, in addition 

 to the regular training series, a series of test trials. The object 

 of the training series was to establish an effective association 

 between the turning response to pain and the auditory stimulus ; 

 the object of the test trials was to determine the degree to which 

 an effective association had been formed. In these tests the pro- 

 cedure was the same as in the training series except that no pain 

 was given. If the negative response had been transferred to the 

 auditory stimulus, they should turn and retrace the path when 

 the buzzer was sounded. A correct response consisted of an 

 immediate turn when the auditory stimulus was presented, or 

 of traversing the whole length of the path into the food-box 

 in the 30 per cent of trials in which no stimulus was given. 

 Progress was measured by the increasing percentage of correct 

 response during the test trials. For in each group the established 

 negative response to pain prevented the animals from responding 

 to sound during the training series. They would most often 

 have turned around or be turning around when the auditory 

 stimulus was given. It is obvious, therefore, that the new stim- 

 ulus which was to be associated with the turning response oc- 

 curred after the act of turning had been initiated. A correct 

 response in the regular training series is the same as it was before 

 the auditory stimulus was introduced, i.e., an immediate turn 

 when the pain stimulus was presented, or traversing the whole 

 length of the path into the food-box in the 30 per cent of trials 

 in which no stimulus was given. 



The number of animals used, the number of training trials 

 necessary to make the association, and the percentage of correct 



