An interval scale of brightness for the pigeon

Abstract

Pigeons were required to discriminate between identical and different pairs of lights in a same/different signal-detection task. If the two lights projected onto the stimulus field, which was mounted behind the center response key in a three-key chamber, were identical in intensity, a single peck on the left key was reinforced with food. If the two lights differed in intensity, right-key pecks were reinforced. Each pigeon experienced all possible pairs (45) of 10 levels of light intensity. The percentage of correct responses was taken as an ordinal measure of the brightness difference between the lights constituting a pair, and was used to determine interval scales of brightness in the pigeon. The brightness scale for pigeons was similar to that obtained from human subjects in judging brightness differences. © 1987 Psychonomic Society, Inc.