COLOR BLINDNESS OF CATS 139 



and as good evidence of failing to do so when the buttons were 

 concealed by shields. 



Our experiments show that the cat has very defective day- 

 light vision as compared with that of human beings. Is it 

 possible that this defective vision accounts for the behavior of 

 Thorndike's cats which clawed at the place where the loop had 

 been when the loop was no longer there ? For such vision as 

 the cat possesses, a mad scramble would conceivably be a much 

 quicker way to lay hold of a loop than an attempt to see it. An 

 accident of similarity of brightness between the loop and the 

 background might render it well nigh invisible to the animal. Is 

 it possible that the poorer the vision an animal possesses the 

 more he becomes dependent on kinaesthetic sensations, which 

 Watson has shown to play a fundamental role in the life of some 

 animals. 



Our records show that an animal may make more than fifty 

 per cent of right choices throughout a large number of trials 

 and yet not learn to discriminate between the two objects. 



Our experience shows that the possibility of the texture error 

 should be guarded against, as well as the error due to improvement 

 by training. In some cases discrimination occurred only after 

 eight hundred trials. 



So many criticisms have been made of the use of colored papers 

 that one advantage in using them, no matter how trifling it be, 

 should be welcome. All the confusions made by these cats can 

 be exhibited to the eye by pasting the papers on gray cardboard. 

 The result of viewing the papers will be a better conception of 

 the nature of the cats' vision than can be got from reading pages 

 of description of their behavior in the experiments. 



Finally we asked two persons of dichromatic vision to sort 

 these colored papers as Holmgren worsteds are sorted. Each of 

 the dichromates made five confusions which had been made by 

 the cats. Both of the dichromates and the cats agreed in the 

 matches (confusions) of two pairs of colors, and for each of 

 these pairs the flicker-equivalents were identical. 



Our account of our exploratory tests of the cats' vision is 

 finished. We hope that feline vision may now be studied quanti- 

 tatively, by means of apparatus which permits of accurate 

 measurement of the wave-lengths and intensities of the lights, 

 as they reach the eye of the animal. 



