The Journal of 



Comparative Neurology and Psychology 



Volume XVI MARCH, 1906 Number 2 



THE ESTABLISHMENT OF AN ASSOCIATION INVOLV- 

 ING COLOR-DISCRIMINATION IN THE CREEK 

 CHUB, SEMOTILUS ATROMACULATUS. 



BY 



MARGARET F. WASHBURN AND I. MADISON BENTLEY. 



The only experimental evidence hitherto existing, so far as we 

 have been able to learn, that fish possess the power to discriminate 

 colors is contained in the work by Vitus Graber, published over 

 twenty years ago and entitled Grimdlinten zur Erforschung des 

 HelUgkeits- und Farbensinnes der Tiered Graber experimented 

 on a large number of animals, including two species of fish, Cobitis 

 barbatula and Alburnus spectabilis. His method was to offer the 

 animals the choice betw^een two compartments differently illumi- 

 nated, and at the end of a given period to count the number in each 

 compartment. The results thus tested light-preferences rather 

 than light-discrimination merely. Graber himself points out 

 that the two do not coincide, inasmuch as an animal may be quite 

 capable of distinguishing between two colors and yet find them so 

 nearly equal in feeling-value that it seeks them equally often. 

 There must also be reckoned with the possibility that apparent 

 color-preferences are really brightness-preferences, due to the 

 difference in brightness between the two stimuli employed. 

 This latter difficulty Graber avoided in the following manner: 

 If an animal showed itself to be, in our modern phrase, positively 



'Rough experiments performed some years later by W. Bateson (Jour, of the Marine Biol. Assoc. 

 of the United Kingdom,!^. S., Vol. 1, 1889-90, p. 225) gave, as the author says, "chiefly negative results.'^ 

 Bateson fed young mullet with minced worms sprinkled on tiles of various colors and noticed that the 

 light-colored tiles were first cleared of food. It is to be remarked that Bateson was working for prefer- 

 ence and not for discrimination of color and also that he neglected to control the element of brightness. 



