A Psychometric Hue Discrimination Function and Unitary Set of Wavelengths Which Have Equal Psychological Spacing for the Pigeon

Abstract

Pigeons were trained to discriminate between two wavelengths (420-470, 470-520, 520-570, 570-650 and 470-650 nm) with a yes/no procedure.The post-discrimination gradients were analysed with the signal detection methods, and a psychometric hue discrimination function ranging from 420 to 650 nm was obtained.A set of discrimination indices (d') was linearly related to wave-number differences, and lines were fitted to the data points. The slope values showed that the visible spectrum was grouped into four sets of wavelengths where there is a slow change in hue and three sets of wavelengths where there is a rapid change in hue.