2 'Journal of Comparative Neurology an J Psychology. 



J. and B., which served as subjects in the present work and upon 

 other monkeys. In addition to continuing the tests upon color 

 vision, steps are being taken thoroughly to test the delicacy of the 

 white-light vision of the monkeys and their sensitivity to differences 

 in the size and form of visual stimuli. 



In view of these further tests, which are concerned with the 

 nature and delicacy of the visual reactions as a whole of this animal, 

 it would seem to be premature in this preliminary report to enter 

 into any general discussion of color vision in animals or to take up 

 the related structural facts which bear upon color vision. The 

 color vision of several different species of animals is being tested in 

 the various laboratories and for this additional reason the writer 

 will confine his statements on the historical side strictly to the work 

 of Kinnaman, which, so far as the writer is aware, is the only 

 study of the color vision of this animal which can lay any claim 

 to scientific accuracy. 



Kinnaman's^ work was certainly as careful and as exact as his 

 method would permit. His stimuli were obtained by means of light 

 reflected from pigmented papers. The method was roughly as fol- 

 lows : A board, 1 inch by 7 inches, and 5 feet long contained six 

 holes pierced at regular distances. Each hole was large enough 

 to admit the bottom of a cylindrical glass. The convex surface of 

 each glass was covered with colored papers or with different grays. 

 Food was kept with one of the colored glasses, the position of which 

 could be varied at will after each test. The discriminations were 

 made rapidly. "In order to determine whether brightness or color 

 was the basis for discrimination four control tests were made. In 

 three of these, I attempted to determine whether the monkeys could 

 discriminate greys and colors varying by the same degree of bright- 

 ness equally well. If blue and red, for example, with a difference 

 in brightness of 15° (determined by the flicker method) were differ- 

 entiated perfectly, and two grays differing by 15° very imperfectly, 

 then color very probably was the basis of the discrimination in our 

 first series of tests." Both original tests and control tests were 



^American Journal of Psychology, Vol. 13, p. 98. 



