Contents xiii 



PAGE 



vision, the visual discrimination apparatus Motives for 

 discrimination and choice Punishment versus reward as an 

 incentive in animal experiments Hunger as an incentive 

 An electric stimulus as an incentive Conditions for bright- 

 ness vision tests White-black vision Evidence of prefer- 

 ence Check experiments Conclusion. 



CHAPTER VIII 



THE SENSE OF SIGHT: BRIGHTNESS VISION (Continued) . 113 



The delicacy of brightness discrimination Methods of 

 testing the dancer's ability to detect slight differences in 

 brightness Results of tests with gray papers Relation 

 of intensity of visual stimuli to the threshold of discrimina- 

 tion Weber's law apparatus and method of experimentation 



Results of Weber's law tests Practice effects, the train- 

 ing of vision Description of the behavior of the dancer in 

 the discrimination box experiments Modes of choice : by 

 affirmation ; by negation ; by comparison Evidence of 

 indiscriminable visual conditions. 



CHAPTER IX 



THE SENSE OF SIGHT : COLOR VISION 133 



Does the dancer see colors? The food-box method of 

 testing color vision Waugh's food-box method Results 

 of tests Tests by the use of colored papers in the visual 

 discrimination box Yellow-red vision Blue-orange vision 

 Brightness vision versus color vision Brightness check 

 tests Green-blue vision Violet-red vision Conclusions. 



CHAPTER X 



THE SENSE OF SIGHT: COLOR VISION (Continued) . .151 



The use of color filters Testing color vision by the use 

 of transmitted light Green-blue vision Green-red vision 



Blue-red vision Stimulating value of different portions 

 of the spectrum Does red appear darker to the dancer than 

 to us ? Conclusions concerning color vision Structure of 

 the retina of the dancer and its significance. 



