134 



J. C. DeVOSS and rose ganson 



very slight for yellow, as if there the animals approximated the 

 brightness-difference-threshold of the human eye. 



The deviations probably show much more the defects of colored 

 papers. They are complex colors and while one factor, say the 

 tint, may presumably brighten the paper, another, say the red 

 or violet, darkens by at least an equal amount. Thus RT1 is 

 very much brighter than R for the human eye, yet the influence 

 of the tint is slight in comparison with the influence of the red 



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%**£* 



jo 



sr 



Figure 4 



for the animal. Hence it is still confused with red. RT2, how- 

 ever, is discriminated from R after many trials, but darkened 

 orange-red is confused. The relations are shown in the following 

 tabulation. 



* Based on our standard of twenty-four correct choices out of thirty-trials, as 

 the test for discrimination. 



