i6o 



The Dancing Mouse 



TABLE 23 



GREEN-BLUE TESTS 



Brightnesses Different for Human Eye 



Green 18 candle meters Blue 18 candle meters 



As it was now evident that the intensity difference was not sufficient 

 to render discrimination easy, the blue was reduced to o, and the green 

 left at 18. 



8 



Now the brightnesses were made, green 64, blue 18, just the reverse 

 of those of series of Table 22. 



10 | 17 | 8 | 2 | 8 | 2 



Each of these series consisted of 20 tests instead of 10. As 

 a result of the arrangement of the lights just mentioned, the 

 green appeared to me very much brighter than the red when 

 it was on the right and very much darker when it was on 

 the left. If this were true for the mouse also, it is difficult 

 to see how it could successfully depend upon brightness for 

 guidance in its choices. Such dependence would cause it to 

 choose now the green, now the red. 



The first four series of green-red tests so clearly demon- 

 strated discrimination, of some sort, that it was at once 



