146 The Dancing Mouse 



how one set of results made possible the interpretation of 

 others. 



As the results of my color vision experiments seemed to 

 indicate that the red end of the spectrum appears much 

 darker to the dancer than to us, tests were now arranged 

 with colors from adjacent regions of the spectrum, green and 

 blue. The papers used were the Bradley green and tint 

 No. i of the blue. They were not noticeably different in 

 brightness for the human eye. Green marked the box to 

 be chosen. Three of the individuals which had previously 

 been "used in the light blue-orange series, and which therefore 

 had perfect habits of going to the light blue, were used for 

 the green-light blue tests. Of these individuals, No. 1000 

 became inactive on the fifth day of the experiment, and the 

 tests with him were discontinued. Twenty series were given 

 to each of the other mice, with the results which appear in 

 Table 20. To begin with, both No. 4 and No. 5 exhibited a 

 preference for the light blue, as a result of the previous light 

 blue-orange training. As this preference was gradually 

 destroyed by the electric shock which was received each time 

 the light blue box was entered, they seemed utterly at a loss 

 to know which box to enter. Occasionally a record of six, 

 seven, or even eight right choices would be made in a series, 

 but in no case was this unquestionably due to color discrim- 

 ination ; usually it could be explained in the light of the order 

 of the changes in the positions of the cardboards. For ex- 

 ample, series 9, in which No. 5 made a record of 8 right and 

 2 wrong, had green on the right for the first three tests. The 

 animal happened to choose correctly in the first test, and 

 continued to do so three times in succession simply because 

 there was no change in the position of the cardboards. I 

 have occasionally observed a record of seven right choices re- 

 sult when it was perfectly evident to the observer that the mouse 



