THE EFFECTS OF VISUAL DEPTH AND ECCENTRICITY ON MANUAL BIAS, INDUCED MOTION, AND VECTION

The relationship between the effects of visual-surround roll motion on compensatory manual tracking of a central display and the perceptual phenomena of induced motion and vection were investigated. To determin e if manual-control biases generated in the direction of surround rota tion compensate primarily for the perceived counterrotation of the cen tral display ('induced motion') or the perceived counterrotation of th e entire body ('vection'), the depth and eccentricity of the visual su rround were varied. In the first experiment, twelve subjects attempted to keep an unstable central display level while viewing rotating visu al surrounds in three depth planes: near (approximately 20 cm in front of the central display), coplanar, and far (approximately 21 cm behin d the central display). In the second experiment, twelve additional su bjects viewed a rotating surround that was presented either in the ful l visual field (0 - 110 deg) or in central and peripheral regions of s imilar width. Manual-control biases and induced motion were shown to b e closely related to one another and strongly influenced both by centr al and by peripheral surround motion at or beyond the plane of fixatio n. Vection, on the other hand, was shown to be much more dependent on peripheral visual inputs.