COLOR BLINDNESS OF CATS 135 



This low stimulating effect of red has been shown for the 

 dancing mouse, the rabbit, and "possibly" 9 for the monkey. 

 Apparently the cat is no exception to the rule. Yet even in the 

 case of red the cat appears to need no such enormous differences 

 in brightness as does the dancing mouse, in order to discriminate 

 promptly. Nevertheless it would be quite unfair to base an 

 opinion of the cat's discriminating ability on his reactions to 

 red. 



DISCRIMINATIONS 



Our account of the confusions made by the cats is complete. 

 Only matters of minor importance are shown by the discrim- 

 inations. To our surprise no trace of individual variations ap- 

 peared in the confusions. This is more apparent because of our 

 determination to employ so many trials that the results would 

 not be vitiated by improvement due to training. 10 



Individual differences did come to light in what we have called 

 difficult discriminations, i. e., those which required at least two 

 hundred forty trials for the animal to learn to discriminate. 

 The greatest difference between any two animals appears in 

 certain colors presented with yellow as the stimulus color. It 

 is indicated by the number of trials required for discrimination 

 by each animal and is shown in the following table. 



There are four prompt discriminations by one cat, only one 

 by the other. The great difficulty of discriminating orange from 

 yellow shown by both animals indicates that it must appear 

 to them very much like the yellow. In this case stopping after 

 five hundred seventy trials would have resulted in a decision 



9 Watson, J. B. Some experiments bearing on the color vision of monkeys* 

 Jour. Comp. Neur. and Psych., vol. 19, 1909, p. 19. 



10 See Yerkes, The Dancing Mouse, pp. 127 and 128. 



