The Sense of Sight: Color Vision 137 



the latter they were promptly pushed to one side by the ex- 

 perimenter and the box, as well as the food, was removed to 

 a new position. 



The results of the tests appear in Table 15. No record 

 of the choices in the first two of the 17 series was kept. The 

 totals therefore include 15 series, or 300 tests, with each 

 individual. Neither the daily records nor the totals of this 

 table demonstrate choice on the basis of color discrimination. 

 Either the dancers were not able to tell one box from the 

 other, or they did not learn to go directly to the orange box. 

 It might be urged with reason that there is no sufficiently 

 strong motive for the avoidance of an incorrect choice. A 

 mistake simply means a moment's delay in finding food, and 

 this is not so serious a matter as stopping to discriminate. 

 I am inclined, in the light of result of other experiments, to 

 believe that there is a great deal in this objection to the method. 

 Reward for a correct choice should be supplemented by some 

 form of punishment for a mistake. This conclusion was 

 forced upon me by the results of these preliminary experiments 

 on color vision and by my observation of the behavior of the 

 animals in the apparatus. At the time the above tests were 

 made I believed that I had demonstrated the inability of 

 the dancer to distinguish orange from blue, but now, after 

 two years' additional work on the subject, I believe instead 

 that the method was defective. 



The next step in the evolution of a method of testing the 

 dancer's color vision was the construction of the apparatus 

 (Figures 14 and 15) which was described in Chapter VII, 

 p. 92. In connection with this experiment box the basis 

 for a new motive was introduced, namely, the punishment, 

 of mistakes by an electric shock. Colored cardboards, in- 

 stead of the white, black, or grays of the brightness tests, 

 were placed in the electric-boxes. 



