CATCHING BALLS - HOW TO GET THE HAND TO THE RIGHT PLACE AT THE RIGHT TIME

Information specifying the future passing distance of an approaching o bject is available (in units of object size) in the ratio of optical d isplacement velocity and optical expansion velocity. Despite empirical support for the assumption that object size can serve as a metric in the perception of passing distance, the present series of experiments reveals that in catching a ball subjects do not rely on such ''point-p redictive'' information. The angle at which (real and simulated) balls approached the subject systematically affected verbal and manual esti mates of future passing distance, as well as the kinematic characteris tics of catching movements. To catch a ball, the actor uses momentary action-related information instead of spatiotemporal estimates. The ha nd velocity is geared to information specifying the currently required velocity. This secures ending up at the right place in the right time , regardless of where this may be.