The discrimination of absolute versus relative brightness in the ring dove, Turtur risorius.

Abstract

Two ring doves, T. risorius, were given 1000 trials each in a modified Yerkes-Watson discrimination apparatus, in an attempt to develop a discrimination of absolute versus relative brightness. Hering grey papers nos. 1, 26, and 50 were used as stimuli. In each presentation no. 26 grey, the standard, was paired with either variable no. 1 or no. 50. After 500 trials one dove showed rapid improvement, making approximately 80% correct responses in the last 300 presentations. The other dove showed less improvement, results being complicated by a position habit. In both cases there was a slight "preference" for the lighter stimulus. Evidence favors the view that discrimination based on relative stimulus factors in the set-up is easier than discrimination based on absolute cues, but the latter can be established with prolonged training and a technique which favors isolation of a specific stimulus.