RATE OF LEARNING IN THE WHITE RAT 17 



between a closed door and an electric shock, and farther on in 

 this report it will often be referred to as learning the negative 

 response to pain. 



From the above conditions it will be noted that no stimuli 

 are given in 30 per cent of each series of trials. This, together 

 with the fact that chance and position habits are of so little 

 significance in the solution of the problem, led us to hold a rather 

 rigid standard as to the number of trials and the percentage of 

 correct reactions to be required of all animals. No animal was, 

 therefore, considered to have mastered the problem until be had 

 made 90 per cent correct responses on the last 100 trials. All 

 animals used in the experiments reported below were first re- 

 quired to learn this negative response to pain. When this was 

 accomplished an electric buzzer was introduced, by means of the 

 timing apparatus, in a certain definite temporal relation to the 

 electric shock, pain. The animals were divided into groups and 

 each group was set to work upon the problem of transferring 

 this negative response from pain over to buzzer, but each group 

 worked with a different time interval. To some groups the 

 stimuli (buzzer and pain) were presented in a forward direction; 

 to others, in a backward i.e., some groups received the buzzer 

 followed by pain, others, pain followed by buzzer. In the test 

 series the order was always buzzer followed by pain. The prob- 

 lem in each group is to learn to respond to the sound stimulus 

 as they have been responding to pain. It is a transfer of re- 

 sponse from pain to sound over certain given time intervals. 

 Continuous presentations and one, two, four, and six second 

 intervals were studied. In the work with the first of the above 

 groups special test series of 10 trials each were given after each 

 20 trials to determine to what extent the transfer had been made. 

 In the remaining groups the time interval was sufficiently large 

 to determine this without these special tests. The standard for 

 mastery in each of these groups is the same as before, 90 per 

 cent on the last 100 trials. 



As the animals completed this problem they were regrouped 

 and set to work on a third problem, but in the regrouping no 



