Eye movements and the selection of optical information for catching

The direction of gaze during a single-ball throwing and catching task was a nalyzed to generate hypotheses regarding the optical information that parti cipants used. Five intermediate and 5 expert jugglers threw and caught a si ngle 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 v ideo recording of the ball and hand revealed that all participants viewed t he ball at or around the ball's zenith. Intermediates varied only the mean phase of viewing across frequencies. Experts, however, varied the initiatio n of viewing, the point of minimum gaze to bail distance, the mean viewing phase, and the mean time between viewing and catching across frequencies. B oth groups initiated the final downward movement of the hand toward the cat ch 89 msec after the bait's zenith. The implications of these results for t he optical information for catching and expertise in a perceptual-motor tas k are discussed.