Dorsoventral asymmetry of colour discrimination in bees

Colour discrimination performance of honeybees was examined by training bee s to a two-coloured disc presented on a vertical plane. Access to the food reward was through the centre of the disc. In one experiment, the upper hal f of the disc was yellow, and the lower half blue. In another experiment, t his was vice versa. In either case, the learned disc was tested against eac h of a series of ten discs whose colour differed in either the upper or the lower half. A comparison between the results obtained in the two experimen ts reveals that colour discrimination is significantly better in the lower half of the frontal eye region than it is in the upper half. The results, s imilar to earlier results obtained in pattern discrimination tasks, cannot be explained by peripheral eye-region-specific specializations. It is propo sed that the functional significance of the lower frontal visual field is b ased on more central neural mechanisms that might constitute an adaptation to the forager's natural needs.