104 HAROLD C. BINGHAM 



size and brightness vision, was given more than 1500 tests. 

 The work done with it is the only experiment of value that 

 was made on form perception. 



The experiment on form discrimination with No. 21 may be 

 divided into three parts: (1) A preliminary investigation; 

 (2) reactions to the triangle -circle and (3) reaction to the circle- 

 triangle. When the work on form perception was begun, I 

 had learned how to get much more work out of my subject 

 and, at the same time, less energy was called forth than in the 

 earlier tests. No. 21 knew me quite well by this time. It was 

 perfectly contented to leave the other birds in the chick-room 

 and go alone with me to the dark-room for work. The chief 

 reason for this was the fact that it always had its morning meal 

 in the dark-room. As soon as we reached the experiment room 

 it was fed a little chick food and allowed to run freely about 

 until the apparatus was made ready for the tests. While I 

 was preparing the apparatus, the chick -would follow me about 

 the room (then lighted) twittering and contented, but if I left 

 it alone for a few minutes its dissatisfaction was made known 

 by loud and persistent peeping. 



When everything was ready the chick was placed in the 

 apparatus. At this point the note in its voice changed very 

 noticeably. I cannot describe this sound, except that it was 

 a slightly modified, I believe it might be called a modulated, 

 "hovering twitter." Very commonly this peculiar sort of sing- 

 ing changed as the bird entered the discrimination chamber, 

 to the "food twitter" which was continued all the time it was 

 inspecting and comparing the two stimulus areas and, of course, 

 after it had entered the nest box for there it was rewarded by 

 finding a few grains scattered in the litter. In this manner a 

 series could be completed in about 15 minutes after which the 

 chick was taken from the experiment box and given more food 

 and its freedom in the room. This procedure could be carried 

 out until the chick's hunger was satisfied after which the tests 

 went so slowly and with such uncertainty that it was found 

 best to postpone the work until the following morning. As 

 the bird became older this mode of experimentation could be 

 carried on as long as three hours. 



While I was preparing test sheets or taking notes at my 

 desk between experiments, No. 21 would crowd up abouf my 



