Independent effects of pictorial displays on perception and action.

Although pictorial illusions have been used to study perception for a long time, the effects of such displays on the visual control of actions has recently been the matter of some debate. Evidence from a re-analysis of an earlier study is presented that suggests pictorial displays can exert opposite effects on perceptual size judgements and grip scaling, perhaps because the two-dimensional elements surrounding the target for a grasp are treated as potential obstacles. This interpretation was supported by the results of an experiment in which the relative position and distance of two-dimensional elements flanking a target had differential effects on perceptual judgements of size and the scaling of grip aperture.