Cole and Long, Visual Discrimination in Raccoons. 66i 



of flicker with the grays just lighter and just darker than the one we 

 were using as a standard. 



After a group of colors corresponding to a certain gray had been 

 selected the proportions of black and white in the gray were deter- 

 mined by comparing it with a composite disk of the Bradley black 

 and white. This involved a comparison of a moving with a motion- 

 less disk of a different texture and doubtless our judgments here are 

 not especially accurate. However, the figures which give the propor- 

 tion of white in each gray disk serve merely as descriptive terms in 

 Table 1 and have nothing to do Avith the experiments. 



The tests of the colors by the flicker method were made in as high 

 an illumination as the observers found at all practicable between the' 

 hours of ten a. m. and three p. m. on cloudless days. The experi- 

 ments with the raccoons were conducted in a very much lower illumi- 

 nation but during the same hours. The papers, both gray and colored, 

 had been in the laboratory about one year at the beginning of the 

 tests. They were kept covered in the drawers of the paper case which, 

 we may add, w^as not resorted to by students. It is evident from 

 the notes of fading in Table 1 that some of the colors were not as 

 dark as recently purchased papers. Tor example, violet shade 1, and 

 red orange shade 2, which, on June 28th matched Gray I^To. 25, had 

 faded by December 27th to match Gray ITo. 20 and, therefore, they 

 appear in both groups. 



After the brightness of the papers of Group 5 had been determined, 

 they were sent to Professor Titchener in order to ascertain whether 

 our use of the flicker method had been reasonably accurate. He wrote 

 us as follows: "I have no objection, then, to your quoting me (if 

 you care to do so) to the effect that by this method the first four disks 

 were practically equivalent and the fifth only a little out of the way 

 by being too bright." . . . "You may say, I think, that the 

 animals judged these four by color alone, provided, of course, that we 

 make the initial assumption that their scale of brightness values 

 coincides with our own." The "first four disks" were violet-blue tint 

 2, orange-yellow shade 1, red-violet tint 1, and red-orange tint 1. 

 Under the high illumination that we used, red-orange tint 1 gave a 

 just noticeable sensation of flicker. 



