174 M. F. WASHBURN AM) EDWINA ABBOTT 



7. Although Series 32 was the first which Polly made, and 

 involved getting acquainted with the apparatus and the situa- 

 tion in general, she had made decided progress towards learning 

 the discrimination at the end of 180 tests: her percentages for 

 the first eighteen days were 60, 55, 50, 70, 50, 61, 56, 65, 50, 95, 

 60, 60, 70, 100, 90, 80, 70, 80. 



It may therefore be concluded that like the other rabbits 

 tested, she found it impossible, in the time allowed, to learn 

 to distinguish between red and a grey of the brightness of Hering 

 grey number 46, that is, a grey dark enough to be called black. 



Supplementary tests on binocular vision 



The rabbit has a small field of binocular vision, if we judge 

 by the angle through which both eyes can be seen at the same 

 time, a test which Waugh has applied to the mouse. In order 

 to get some light on the question as to how much use the rabbit 

 makes of binocular vision as compared with monocular vision, we 

 made some simple tests on Polly. When she was sitting still, 

 two bits of lettuce of equal size were held out, one straight in 

 front of her nose at a distance of three or four inches, the other 

 in line at right angles, directly in front of her left or right eye, 

 and at an equal distance. Out of fifty trials the rabbit only 

 twice took the bit of food held in front. The other forty-eight 

 times, after sitting motionless a few seconds, she turned her 

 head to the side and took the food offered there. It would 

 appear that her actions were determined rather by monocular 

 than by binocular vision. The rabbits seemed from our general 

 observation of them to be influenced by binocular vision to a 

 certain extent in their movements: that is, they seemed to 

 avoid by vision objects directly in front of them. We often 

 noticed in the box experiments, however, that a rabbit would 

 turn its head from side to side before making a choice: 

 sometimes a record like the following would be made: "Rabbit 

 starts towards red, stops, looks at grey, turns back to 

 red and pushes it." The experiments on Polly, just described, 

 indicate that when a rabbit turned its head so as to face one 

 of the doors, it was really looking, monocularly, at the other 

 door. Thus the looking at grey described in the record was 

 probably merely a turning of the head so as to get a better, 

 that is, a monocular, view of the red before pushing it. And in 



