PARTIAL VISUAL FEEDBACK AND SPATIAL END-POINT ACCURACY OF DISCRETE AIMING MOVEMENTS

Five experiments are reported in which the effect of partial visual fe edback on the accuracy of discrete target aiming was investigated. Vis ual feedback was manipulated through a spectacle-mounted liquid-crysta l tachistoscope. The length of the visual feedback interval was varied as a percentage of the instructed movement time. In Experiment 1, the length of the vision interval was manipulated symmetrically at the be ginning- and end-phase of the movement, whereas in the remaining exper iments, the vision time was varied with respect to the end-phase only. The variations at the end were examined for different distances (Expe riment 2), different movement speeds at the same distance (Experiment 3), and in small interstep intervals (Experiment 4). A vision time of more than 150 ms at the end-phase of the movement enhanced aiming perf ormance in all experiments. Longer vision times monotonously improved aiming accuracy; the fifth experiment showed that a vision time of abo ut 275 ms was sufficient for near-perfect aiming. Furthermore, the sig nificance of vision during the first phase of a movement was demonstra ted again. The results of the five experiments pointed to shorter visu omotor processing times. To explain the beneficial effects of short vi sion times for aiming accuracy, we propose a model of visuomotor proce ssing that is based on the stochastic optimized submovement model of M eyer, Abrams, Komblum, Wright, and Smith (1988).