

66 



HAROLD C. BINGHAM 



To Professor Yerkes, under whom this study was made and 

 i,, whom I am indebted for assistance and suggestions, credit 

 is due for many of the points of method here described. A 

 report has been published by him and Professor Watson 1 in 

 which the details of parts of the apparatus have been presented. 

 For the detail of divisions 2 and 3 the reader is referred to the 

 Yerkes and Watson report. In order to give a comprehensive 

 idea of the mechanism, I shall describe the complete apparatus 

 as it appeared during my work, abbreviating, as much as possible, 

 descriptions .of the parts which have been previously described. 

 Figure 1 is an isometric view of the apparatus as a whole 

 showing only the skeleton of the different parts when assembled 

 for experimental work. I shall speak of that part of the mechan- 

 ism labelled I as the experiment box. The opposite end, III, is 

 the light or source box. Between the experiment box and the 

 source box is a stimulus shifter, II. The whole apparatus was 

 set up in a dark room. The only sources of illumination were 

 the lamps in the source box and a lamp, L, hanging directly 

 above the experiment box. With these sources cut off, a dark 

 adapted human eye could see slightly, for a few small cracks 

 in the room allowed faint rays of light to enter; but the sub- 

 sequent description will show that these factors were of no 



consequence. 



As a means of testing the chicks' ability to discriminate 

 between sizes and forms, two illuminated areas differing from 

 each other with respect to one or both of these factors are simul- 

 taneously exposed before the experiment box, I. The problem 

 for the animal is to learn regularly to choose one of these stimuli 

 and to reject the other. It is punished by means of an electric 

 shock for a wrong choice and is rewarded for a right choice 

 by escape to a warm, dry nest box where food, light, water, 

 and companionship are to be found. The illumination of the 

 visual stimuli comes from the source box, III, which is con- 

 structed so that the brightness of either stimulus area may be 

 independently controlled. The light is admitted to two of 

 three regulated apertures in the shifter, II, the function of 

 which is to facilitate changes in the size, form, or relative posi- 

 tion of the stimulus areas. 



• Yerki rl M. and Watson, John B. Methods of studying vision in ani- 



mals. !■ Monographs, 1911, vol. 1, no. 2, S. N. 2. 



