INSTINCTS AND HABITS IN CHICKS 63 



included in the curves. In a comparison of results for the two 

 groups two things especially must be taken into consideration, 

 (i) the natural preferences before training began and (2) pre- 

 vious training. In regard to the first, Group II had to overcome 

 a stronger preference for the larger of the two openings. The 

 chicks of Group I took the smaller opening more often than 

 those of Group II, perhaps because in general the black-blue 



training inclined chicks to accept the stimulus of lower bright- 

 ness value, which in this case has been shown to be on the side 

 of the smaller opening. The previous brightness training here 

 came into conflict, however, with the natural (?) tendency to 

 pass out by the larger opening, which may be something more 

 than a brightness preference, and thus may be explained the 

 small difference between the two groups in the results of the 

 preference trials. As to the second point above. Group I, besides 

 acquiring the black-blue habit, had become habituated to the 

 general conditions of the apparatus in such a way that adjust- 

 ment to the new conditions of the size experiment must have 



