Colour and Brightness Preferences in the Lizard Anolis Carolinensis

Abstract

Lizards of the species Anolis carolinensis were tested for colour and brightness preferences by using the phototaxic response. A choice was given between two alleys leading to frosted Perspex panels back-projected with light varying in hue and brightness, the variation being controlled by Munsell colour and neutral-density filters. Five colours were combined with several levels of brightness in a series of tests from which estimates could be made of relative preferences. The assumptions that the effects of hue and brightness combine additively to determine preference, and that relative preferences are independent of pairing, were tested by attempting to fit an appropriate linear model to the data. Choice proportions for any comparison were plotted on a normal probability scale against filter density, and it was found, to a reasonably close fit, that the preference for any particular colour increased linearly with filter density on the comparison colour. The rate of increase was approximately the same for all comparisons, and it was possible to use the y intercepts of the regression lines of preference against filter density as a measure of the scale values of the preferences for each colour. Scale values remained invariant over comparisons, with one exception: the preference for red over yellow was greater than predicted from the comparisons of these two colours with others. This may be a contrast effect.