Hemispheric asymmetries in categorical judgments of direction versus coordinate judgments of velocity of motion.

Three experiments on visual field differences in motion perception are reported. Experiment 1 employed circular stimuli that grew or shrank either quickly or slowly. Experiments 2 and 3 employed circles that moved upward or downward either quickly or slowly. Judgments based on categorical equivalence classes (i.e., grow/shrink, upward/downward) generally yielded small and nonsignificant right visual field advantages. Judgments based on the precise coordinates of motion (i.e., quickly/slowly) yielded significant left visual field advantages across all three experiments. Results are interpreted in light of Kosslyn's (1987) model of hemispheric differences in the processing of categorical versus coordinate spatial relations.