468 'Journal of Comparative Neurology and Psychology, 



edly disagreeable to the experimenters and the mice reacted to 

 it vigorously. Its value was subsequently ascertained to be 500 

 ±50 units. For the medium stimulus we tried to select a value 

 which should be about midway between these extremes. In this 

 we succeeded better than we could have expected to, for comparison 

 indicated that the value was 300 ± 25 units. Fortunately for the 

 interpretation of this set of results, the exact value of the stimuli 

 is not important. 



By the use of our calibrated inductorium and the measurement 

 of our primary current, we w^ere able to determine satisfactorily the 

 stimulating values of the several currents which were used in the 

 experiments of sets II and III. The primary current of 1.2 

 amperes, which was employed, served to actuate the interrupter 

 of the inductorium as well as to provide the stimulating current. 

 The interruptions occurred at the rate of 65 ±5 per second. We 

 discovered at the outset of the work that it was not worth while 

 to attempt to train the dancers with a stimulus whose value was 

 much less than 135 units. We therefore selected this as our weak- 

 est stimulus. At the other extreme a stimulus of 420 units was 

 as strong as we deemed it safe to employ. Between these two, 

 three intermediate strengths were used in the case of set II, and 

 two in the case of set III. Originally it had been our intention 

 to make use of stimuli which varied from one another in value 

 by 60 units of stimulation, beginning with 135 and increasing by 

 steps of 60 through 195, 255, 315, 375 to as nearly 425 as possible. 

 It proved to be needless to make tests with all of these. 



We may now turn to the results of the experiments and the inter- 

 pretation thereof. Before the beginning of its training each mouse 

 was given two series of tests in which the electric shock was not 

 used and return to the nest-box through either the white or the 

 black box was permitted. These twenty tests (ten in series A and 

 ten in series Bj have been termed preference tests, for they served 

 to reveal whatever initial tendency a dancer possessed to choose 

 the white or the black box. On the day following preference 

 series B, the regular daily training series were begun and they were 

 continued without interruption until the dancer had succeeded 

 in choosing correctly in every test on three consecutive days. 



Results of the experiments of set I. The tests with the weak 

 stimulus of set I were continued for twenty days, and up to that 

 time only one of the four individuals in training (no. 128) had 



