VISUAL PERCEPTION OF THE CHICK 



55 



was varied according to the plan of the second and third col- 

 umns. The illumination of the electric compartments was con- 

 trolled as indicated by the last two columns. In tests 1 and 2, 

 the + or correct stimulus area was considerably brighter and 

 the corresponding compartment lighter than the other. In 



TABLE 5 



Control series for Q 2S-\ ©7+ Discrimination 



Nos. 15, 16, 17, 18, 20, and 21 



March 4, 1912 



Record Sheet 1. Series 14 



tests 3 and 4 the general illumination was reversed without 

 changing the brightness or luminous intensity of the stimulus 

 areas. After test 5,^ the source controls remain unchanged 

 although the relative position of the + or correct stimulus 

 varies from right to left. 



This represents the first specific control for o 28+ — Q 7 + 

 discrimination after a varying amount of preliminary training 

 had been completed. If a chick could not react correctly under 

 these conditions, it was assumed that the preliminary training 



^In test 5, the source distances were equal and no controls were introduced. 



