VISUAL PERCEPTION OF THE CHICK 77 



preference series, such a procedure was followed while the chick's 

 learning was being studied. The two phases of the general dis- 

 crimination problem, therefore, cannot be sharply separated, but 

 throughout the present chapter they will be regarded as distinct, 

 and referred to as the primary and secondary tasks in the forma- 

 tion of the discrimination habit. 



2. Individual characteristics 



On December 21, work was started upon a problem in flicker 

 discrimination with five chicks belonging to the fourth group. 

 The chicks were at that time approximately one week old. The 

 present remarks will be confined chiefly to three individuals, 

 chicks 24 9 , 25 9 , and 27 9 . The other two chicks shortly suc- 

 cumbed to the confinement of the laboratory. No. 24 was char- 

 acterized in my notes as rugged and next in size to No. 25. No. 

 25, a White Plymouth Rock, remained from the first robust and 

 oversized.^ No. 27 was somewhat undersized. Chicks 24 and 

 27 were Barred Plymouth Rocks. 



On the first day each of the chicks was allowed to escape ten 

 times at either exit. This was the first preliminary series. The 

 positive stimulus was displayed first at the left, and thereafter 

 alternately at the right and the left. Six tests were made in the 

 morning and four in the afternoon. During the morning tests the 

 exits were wide open. In the seventh test, the doors were nearly 

 closed and thereafter were completely closed. In the eighth, 

 ninth, and tenth tests and in the series following, the door of the 

 exit was opened as soon as the chick had chosen the compartment. 



On December 22, the second preliminary series was similarly 

 started. Four tests were given in the morning, three in the 

 afternoon, and the remaining three in the morning of the follow- 

 ing day. In these two preliminary series, no preference for either 

 of the stimuli was noticeable. Table 11 summarizes the choices 

 with reference to the stimuli which, in subsequent training, 

 became plus ( + ) and minus ( — ) signs. The table Indicates 

 that there was no preference for either stimulus. 



Certain right or left preferences, on the other hand, are to 

 be found. Table 12 summarizes these tendencies. No. 27 

 shows a distinct preference for the left side but chicks 24 and 

 25 manifest no preference. 



^In comparison with the chicks of the group. 



