Ecological relevance of stereopsis in one-handed ball-catching

The aim of this study was to compare one-handed catching performance betwee n catchers with high (n = 10) and low (n = 10) binocular depth vision or st ereopsis. In two sessions of 90 trials, tennis balls were projected at thre e different velocities towards the subject's shoulder region. Participants with good stereopsis were more successful, although the difference in numbe r of correct catches fell short of significance. More specifically, catcher s with low stereopsis made more temporal errors, but no differences in spat ial errors. As the velocity of the ball increased, the initiation of the ca tch was delayed and catching performance decreased. The finding that stereo psis affected timing of the catch challenges the 'monocular tau hypothesis' in the control of interceptive timing, while the velocity effect shows tha t the act of catching a ball is nor initiated at a constant time-to-contact .