Stimulus-response compatability for moving stimuli: perception of affordances or directional coding?

Michaels reported a compatibility effect in which responses were fastest at the destination of a moving stimulus; she interpreted this "destination" compatibility effect in terms of catching actions "afforded" by the stimulus motion. The present study evaluated implications of the catching-affordance account and compared them with those of an account based on spatial coding of relative direction. The destination compatibility effect was obtained when the responses were keypresses rather that catching movements of a joystick and regardless of whether the stimulus expanded, contracted, or only changed location. This effect was a function of relative rather than absolute location of the responses. A similar compatibility effect was obtained when destinations were designated by static arrow stimuli. The results are inconsistent with the catching-affordance account and are best explained by the coding of relative direction.