32 HAROLD C. BINGHAM 



showed signs of this weakness were the largest and apparently 

 the strongest of the flock. There was no evidence of it among 

 the chicks of the third and fourth groups, which were fed 

 sparingly and for which the temperature of the brooder was 

 carefully regulated. 



The matter of health among the chicks turned out to be a 

 problem which had not been anticipated. However, it did not 

 prevent work toward the solution of the primary problem. The 

 task originally planned was a study of the chick's discriminative 

 ability between sizes, forms, and brightnesses, but, owing chiefly 

 to these unfavorable conditions, little consideration has been 

 given to the third factor. Later tasks added to the original 

 plan involve the perception of flicker and a study of the learning 

 process and ideational content. 



The aim has been to make the study intensive and quantitative. 

 The question whether the chick can discriminate between stim- 

 uli diff^ering with respect to a single visual detail is only a 

 preliminary aspect of the problem. The primary task has been 

 that of determining the least perceivable difference in detail 

 vision. Breed's work indicates that chicks can discriminate 

 on the bases of size and form. The work of Katz and Revesz 

 suggests the same possibility. My original plan, then, was to 

 determine the threshold of difference for each of these factors. 



With respect to size, my original plan was carried out with no 

 essential changes, but with form, it was found necessary to 

 abandon the original plan. In a short time it appeared that 

 proper responses to stimuli differing only in form were not so 

 readily acquired as reactions to size differences. After trying 

 in vain for several weeks to train different subjects to discrimi- 

 nate between a circle and a triangle equal in area, the nature of 

 the problem was considerably modified. It was clearly neces- 

 sary to determine whether the chick, under the conditions of 

 this experiment, could perceive form differences. 



The task involving flicker perception, like that with forms, 

 demanded first a preliminary answer. Other than the generally 

 observed fact that birds are highly sensitive to moving stimuli, 

 there were no experimental data at hand to indicate that a three 

 or two to one flicker difference could be perceived. Beyond the 

 study of a two to one discrimination, time and conditions have 

 not permitted me to go. 



