EXPERIMENTS ON THE RABBIT 175 



turning the head from side to side, the rabbit is really looking 

 at the object from which its face is turned. 



IV. CONCLUSIONS 



i. The rabbit can discriminate Bradley saturated red paper 

 from Hering grey number 7 (Series, 2, 5, 8, 11, 16, 17, 20, 27, 

 30, 32, t,^); from Hering grey number 15 (Series 1, 6, 7, 12, 

 13, 2i, 22, 31, 34, 36, 37, 38), and from Hering grey number 24, 

 though few tests were made with this grey (Series 3 and 9). 



2. That this discrimination is a true visual discrimination 

 and not one based on smell or some other clue; further, that 

 it is based on brightness rather than on color difference, the red 

 being seen as darker than the grey, is indicated by the fact that 

 the rabbits gave no evidence of ability to discriminate red from 

 "Stoelting black " paper or from the very dark Hering grey 

 number 46 (Series 4, 10, 19, 22, 39), while the ability to dis- 

 criminate was again shown as soon as a lighter grey was used 

 (Series 5, 7, 22). 



3. One short series (Series 13) suggested that Hering velvet 

 black looks darker to the rabbit than Bradley saturated red. 

 Series 22 and t>3 failed to confirm this, and gave no evidence 

 that red was discriminated from Hering velvet black paper. 



4. Red has a very low stimulating effect on the rabbit's 

 retina ; a result which corresponds to what Yerkes has* found 

 for the dancing mouse and Watson for the monkey. Our 

 experiments furnish no evidence that red is seen as a color: on 

 the other hand they do not prove that it is not so seen. The 

 rabbits may simply have found it impossible during the period 

 of the training to base discriminations on color rather than on 

 brightness differences. Whether color difference exists or not, 

 the rabbit evidently attends more readily to a brightness than 

 to a color difference. 



5. The results regarding the brightness value of saturated 

 blue are not conclusive. It seems to be readily distinguished 

 from " Stoelting black " paper (Series 23 and 28), a discrimina- 

 tion which may be based either on brightness or on color differ- 

 ence. That the difference involved is mainly one of bright- 

 ness, the blue looking lighter than the black, is indicated by the 

 fact that blue and grey 7 were not discriminated in the course 

 of 51 experiments by Dark Nose (Series 14), nor in the course 



