INSTINCTS AND HABITS IN CHICKS 67 



E. Some Effects of Modifications 



In table 12 were pointed out the natural color preferences 

 of chick no. 8: white in preference to black, blue to orange, 

 blue to yellow, and yellow to black. The peculiarity of the reac- 

 tions to blue was mentioned. If blue be supposed to have a 

 higher brightness value for chicks than for hiunans, the chick's 

 behavior might be satisfactorily explained on the ground only 

 of brightness of stimulus. Further experimentation was under- 

 taken with a view to an explanation of the above apparent 

 irregularity. No. 11, a chick which had been trained on black- 

 white and had progressed so far that in its last series of twenty 

 successive trials it made but one error, was tested for its pref- 

 erence on the combination of colors listed in table 23. Eight 

 days had elapsed between the date of the 19-1 series and these 

 color preference tests. 



TABLE 23 



Preference Tests After Black- White Training 

 Chick no. 11. Hatched 12/10, '07. Sex, F. 

 Series Date Right Wrong 



Black White 

 Jan. 21 19 1 



Orange White 

 A Jan. 29 8 2 



Black Blue 



B Jan. 29 10 



Blue White 



C Jan. 29 6 4 



Yellow White 

 D Jan. 29 8 2 



This record reports the tests in the order in which they were 

 given, as do other records. Again the reactions to blue seemed 

 somewhat surprising. That blue should be rejected as freely 

 as white, when appearing with black, and that blue and white 

 should be accepted almost indifferently, are not results that one 

 should expect. These facts seem to confirm the hypothesis that 

 blue has a special brightness value for the chick. 



Further investigation followed with six other chicks, inci- 

 dental to the direct line of investigation. Table 24 shows the 

 first preference reactions of chicks nos. 17, 18, 20, 32, 33, and 



