ABSTRACT
Catching a sideward-passing ball requires that one be attuned to an informational variable that will guide the hand to the interception point. Jacobs and Michaels (2004) showed that when participants caught balls swinging down from the ceiling on a thin line, the course of the hand’s movement could be predicted by the ratio of lateral angular optical velocity to rate of expansion. However, support for this variable has been complicated by empirical inconsistencies concerning hand movement reversals (i.e., moving the hand left then right, or vice-versa, over the course of intercepting the ball). Jacobs and Michaels, on the other hand, while it predicts unilateral reversals in the swinging balls case, predicts no reversals with planar ball trajectories. Using the reversal criterion of Montagne et al. (1999), it is observed that no movement reversals on any of the 225 trials in the critical condition. From these results the authors conclude that planar ball approaches are not generally characterized by movement reversals.
