102 HAROLD C. BINGHAM 



triangle is presented along with a circle. Inversion of a triangle 

 produces a marked difference in the distributions of the light 

 which reaches the retina, yet the form of the stimulus is 

 unchanged. 



In the following report of my own tests on form discrimina- 

 tion, it will be noticed that I obtained results as positive as 

 those of Breed when the apex of the triangle was at the top. 

 When the position of the triangle was inverted, however, the 

 perfect reactions ceased. It was so difficult to get a chick to 

 react positively when a square was used with a circle that I 

 found it practicable to make the control test on the distribu- 

 tion of light only in the case of the circle-triangle reaction. It 

 is regrettable that Breed failed to make this control test in 

 his experiments. 



2. Experiments 



The development of my system in the study of the chick's 

 form perception followed, in general, that which occurred in 

 my study of reactions to sizes. Work on this visual factor, 

 i.e., the discriminative ability between circles and triangles 

 which are equal in area, was done with two of the second group 

 of chicks, Nos. 9 and 11. The latter became afflicted with 

 "weak legs" after the 24th series, up to which time it had given 

 no positive results. The results from No. 9 might be regarded 

 as slightly positive. 



On the whole the results in table 6 show a preference for 

 the circle. Series 10 was perfect. One contains 90% of right 

 choices and several reached 70% or 80%. It is not surprising 

 that the chick became discouraged, since I had not yet adopted 

 the plan of beginning with complex stimuli and working toward 

 the simple. A system of control similar to that described under 

 size perception (p. 98) was" used throughout the work. The 

 surprising feature is the high percentage of right choices on 

 January 4 and 5 when the chick was becoming discouraged 

 and frightened. This condition resulted in a rush for one stim- 

 ulus or the other as though "to get the choice over." It appears 

 that there was some sort of a difference between the two illu- 

 minations which tended to catch the eye of the rushing chick, 

 but this was not clearly enough perceived for a dependable 

 basis of discrimination. Finally, this experiment did not def- 

 initely prove, even though we admit a preference for the circle, 



