CHAPTER X 



General Conclusions and Summary 



The results of the preceding study can leave no doubt as to 

 the relative importance of size and form in the chick's visual 

 life. It has been found that the number of tests necessary 

 for the formation of a discrimination habit is much greater for 

 forms than for sizes. Moreover, "there was little difficulty 

 in finding chicks that could readily discriminate sizes, but 

 subjects that could discriminate forms, even after long training, 

 seemed to be less plentiful. This study has also revealed 

 the fact that even after perfect reactions to the circle-triangle 

 are established, the form element as such plays no part in the 

 discrimination. 



The relative discriminative value of size and form was further 

 tested by removing from the visual complex all but one of 

 these factors and comparing the effect of different eliminations 

 upon the chick's choice. The remainder of the complex, 

 exclusive of size and form, was treated as a single factor and is 

 spoken of as "brightness and general illumination." In table 

 18 the result of this special test is summarized from the records 

 of chicks 15, 16, 17, 18, 19, 20, and 21. The averages of this 

 table indicate that size was first in importance. Correct 

 choices (R) on the basis of size difference alone, series 14, are 

 S6 per cent of the total chances. The complex remainder 

 called "brightness and general illumination" stands next, series 

 15, with nearly 70 per cent of correct choices. The average 

 record is lowest when form provided the only discriminable 

 basis, series 12, with correct and wrong choices nearly equal. It 

 thus appears that the relative value of special factors in the 

 chick's vision, arranged in the order of their importance, are 

 size, the complex of brightness and general illumination, and 

 form. 



No certain comparison between the role of flicker and that 

 of size and form can be made on the basis of the present study. 

 However, on the strength of casual observation, it appears 



