1 62 The Dancing Mouse 



instead of the higher illumination, this result may be inter- 

 preted as indicative of dependence upon brightness in the 

 previous color tests. It looks very much indeed as if the 

 green had been chosen, not because of its greenness, but on 

 account of its relatively greater brightness. 



This test of brightness preference was followed by two 

 series, 16 and 17, under conditions similar to those of the 

 first four series of the table. For series 16 the value of the 

 light in the left box was i candle meter, that of the light in 

 the right box 1800 candle meters. Discrimination was per- 

 fect. For series 17 the value for the left remained at i candle 

 meter, but that of the right box was decreased to o. In this 

 series No. 152 was entirely at a loss to know which box to 

 choose. Of course this was an entirely new set of conditions 

 for choice, namely, a colored box, the green or the red as the 

 case might be, beside a dark box, the one which was not 

 illuminated. If the mice really had been choosing correctly 

 because of a habit of avoiding the red or of seeking the green, 

 this method should bring out the fact, for the red box, since 

 with it the disagreeable electric shock had always been asso- 

 ciated, should be a box to be avoided. For No. 151 this 

 seemed to be the case. 



Series 23 to 27 of Table 24 were given as final and crucial 

 tests of the relation of brightness discrimination to color dis- 

 crimination. As it is not possible to express in a simple 

 formula the conditions of the tests, a sample series which 

 indicates the brightness of the colors in each of the twenty 

 tests of a series, and in addition the results given by No. 151 

 in the first of these final series, is reproduced in Table 25. 

 For an animal which had presumably learned perfectly to 

 choose green in preference to red, the record of 8 mistakes 

 in 20 choices as a result of changes in relative brightness is 

 rather bad, and it renders doubtful the existence of color 

 discrimination in any of these experiments. No. 152 showed 



