78 HAROLD C. BINGHAM 



task originally planned was a study of the chick's discrimina- 

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

 chiefly to these unfavorable conditions, little consideration has 

 been given to the third factor. The present paper is a prelim- 

 inary report of a detailed investigation which the writer hopes 

 to complete within a few years. 



As far as the study goes, the aim has been to make it inten- 

 sive and quantitative. In the matter of size and form, the 

 question has been, not merely: Can the chick discriminate 

 between stimuli which differ from each other with respect to 

 one of these factors, but What is the least difference that it 

 can discriminate? Breed's work 4 has indicated that chicks can 

 discriminate on these bases. The work of Katz and Revesz 5 

 suggests the same possibility. My original plan, therefore, was 

 to test this matter quantitatively and to determine the chick's 

 threshold of difference for each of these factors. 



With respect to size, I have carried out my original plan 

 without any essential changes, but in the case of form, I was 

 forced to abandon the plan with which I started. In a short 

 time it appeared that proper responses to stimuli differing from 

 each other only with respect to form were not so readily acquired 

 as reactions to size differences. After I had tried in vain for 

 several weeks to train different subjects to discriminate between 

 a circle and a triangle which were equal in area, the nature of 

 my problem was markedly changed. It was clearly necessary to 

 determine whether the chick, under the conditions of this ex- 

 periment, could perceive form. 



Finally, another aspect of the problem which quite naturally 

 appears in an investigation of this sort is that of the relative 

 value of visual size, form and brightness. My earlier results 

 with forms, negative beyond all doubt, emphasized the desir- 

 ability of considering the factors in combination as well as in 

 isolation. In its normal life the chick is not compelled to rely 

 upon a single visual factor, but, on the contrary, it relies upon 

 a natural combination of visual qualities. It thus seemed 

 to start with complex stimuli and from these grad- 



1 Breed, Frederick S. The development of certain instincts and habits in chicks. 

 Monographs, 191 1. vol. 1, no. 1, S. N. 1; also Reactions of chicks to opti- 

 cal Btimuli, Jour. Animal Behavior, 1912, vol. 2, pp. 280-295. 



D. and Revesz, G. Kxperimentell-psychologische Untersuchungen mit 

 Hunnern. Zeit. j. Psych, u. Physiol, d. Sinnesorgane, 1909, Bd. 50, S. 93. 



