Behavioral measures and theoretical analysis of spectral sensitivity and spectral saturation in the goldfish, Carassius auratus

Abstract

Isolated information is found in the literature about photo-chemical receptor absorptions and physiological responses from several different levels of the goldfish visual system. To integrate this information into a synthesized account of visual response in the intact organism, precise discrimination measures are required. An operant conditioning technique was used to obtain discrimination measures in a two-lever choice situation. To measure photopic spectral sensitivity, the energies of spectral lights required for 75 per cent correct choice responding were determined at 12 points in the spectrum. To measure spectral saturation, the reciprocal of the least colorimetric purity required for 75 per cent correct choice responding to a mixture of spectral light and broad-band tungsten light was determined for the same spectral stimuli. The data indicate that goldfish are sensitive to light over the spectral range of at least 401–755 nm. Furthermore, goldfish, on the basis of the measured saturation discrimination function, probably have trichromatic vision. The form of the saturation function is accounted for by a model of the visual system that postulates a summation of responses from different types of cones of known absorptions to yield a brightness response, and that postulates interactions between activities initiated in the different types of cones to yield opponent chromatic responses at the neural level.