Eye Movements and the Selection of Optical Information for Catching

The direction of gaze during a single-ball throwing and catching task was analyzed to generate hypotheses regarding the optical information that participants used. Five intermediate and 5 expert jugglers threw and caught a single ball continuously with 1 hand while wearing a head-mounted eye tracker to monitor their direction of gaze. Participants were instructed to throw the ball at 3 self-paced frequencies: preferred, one half of preferred, and twice preferred. Analysis of the digital eye tracker data along with the video recording of the ball and hand revealed that all participants viewed the ball at or around the ball's zenith. Intermediates varied only the mean phase of viewing across frequencies. Experts, however, varied the initiation of viewing, the point of minimum gaze to ball distance, the mean viewing phase, and the mean time between viewing and catching across frequencies. Both groups initiated the final downward movement of the hand toward the catch 89 msec after the ball's zenith. The implications of these results for the optical information for catching and expertise in a perceptual-motor task are discussed.