Visual Information: The Control of Aiming Movements

The study examined the contribution of various sources of visual information utilised in the control of discrete aiming movements. Subjects produced movements, 15.24 cm in amplitude, to a 1.27 cm target in a movement time of 330 ms. Responses were carried out at five vision-manipulation conditions which allowed the subject complete vision, no vision, vision of only the target or stylus, and a combination of stylus and target. Response accuracy scores indicated that a decrement in performance occurred when movements were completed in the absence of visual information or when only the target was visible during the response. The stylus and the target plus stylus visual conditions led to response accuracy which was comparable to movements produced with complete vision. These results suggest that the critical visual information for aiming accuracy is that of the stylus. These findings are consistent with a control model based on a visual representation of the discrepancy between the position of the hand and the location of the target.