Accuracy of perceptual processes subserving different perception-action systems

The accuracy of perceptual processes subserving different perception-action systems was evaluated by presenting subjects (N = 17) with similar optic flow patterns, while requiring different actions from them. Squash balls were dropped along a fixed trajectory, and subjects were asked to (a) hit the ball using their own arm, (b) release an artificial arm to hit the ball, and (c) indicate when the ball was at the point of contact of conditions (a) and (b). The variability of the temporal initiation point of the actions, which served as an operationalization of perceptual accuracy, was compared under all three conditions. The results indicated that the variability of the temporal initiation point was smallest under the natural arm condition, even though movement time was more variable here than under the artificial arm condition. It is argued that, because perception and action are intimately interwoven components of a perceiving/acting system, it is not an extrinsically (experimenter-) determined simplicity of perceptual and/or motor aspects of the task, but the intrinsic make-up of this overarching system that determines which couplings lead to a more accurate performance.