180 M. F. WASHBURN AND EDWINA ABBOTT 



him simply to avoid grey as such, we should explain this behavior 

 by saying that blue looked like grey to him here. But in the 

 next series he was given blue and the grey (15) with which he 

 had had most preliminary training, and he chose the grey 70 

 per cent, of the time. 



On the whole, then, the consideration of the possibility sug- 

 gested by Breed's work does not require us to modify our con- 

 clusions. Doubtless the reason why positive avoidance of a 

 given impression as such plays more part in his experiments 

 than in ours is that he used a much stronger punishment for 

 wrong choices than we did ; his chicks were given electric shocks, 

 while our rabbits merely pushed against closed doors. 



9. To a certain degree, the rabbit is able to form a habit of 

 choosing the darker of two impressions, irrespective of their 

 absolute brightness. It has been noted that we have found such 

 a supposition useful in explaining, at several points, the behavior 

 of our rabbits in a new series as due to their experience in previ- 

 ous series. No other hypothesis seems conceivable to explain 

 the results of Series 37, where Polly chose grey 15 72.8 per cent of 

 the time when it was presented with white, and only 27 per cent, 

 of the time when it was presented with red. But the rabbit has 

 no grasp such as human beings would gain of the principle of 

 choosing the darker impression : the absolute brightnesses 

 involved have a disturbing influence, as suggested by the fact 

 that ordinary red-grey series, presented after the complex series, 

 (Series 38 after 37), and after a short grey-white series (Series 

 36 after 35) showed a falling off in the percentage of correct 

 choices, apparently due to the association of conflicting impulses 

 with the grey as such. 



10. There is evidence to indicate that while probably capable 

 of binocular vision, the rabbit uses monocular vision in preference. 



