BASEBALL HITTING, BINOCULAR VISION, AND THE PULFRICH PHENOMENON

Objectives: To determine if dimming the light to 1 eye affects basebal l hitting (motion-in-depth) and if binocular interaction influences th e ability to hit a baseball. Methods: The ability to hit baseballs in a batting cage was measured under conditions of(1) no filter before ei ther eye, (2) neutral density fitters before both eyes, and (3) a neut ral density filter before 1 eye, while viewing with both eyes. Batting scores were based on the number of hits, fouls, and misses. Results: A neutral density filter of 0.6 optical density before both eyes had n o significant effect on batting ability compared with no filter (87% v s 94%). While viewing binocularly, a filter before 1 eye caused a sign ificantly greater reduction in hitting scores than when the filter was placed before the opposite eye (36% vs 80%). This greater effect of I eye on hitting scores denotes an ocular preference or dominance withi n the motion stereopsis system. The eye associated with the greater re duction in hitting ability when dimmed by a filter was termed the domi nant eye for motion stereopsis. In comparison with placing 0.6-optical density filters before both eyes, the same filter before the dominant eye reduced hitting ability (36% vs 87%), but when the filter was pla ced before the nondominant eye, the hitting ability was not significan tly reduced (80% vs 87%). The batting scores decreased as filter densi ties increased from 0.3- to 0.6-optical density, and the effect was si gnificantly more for the dominant eye than for the nondominant eye. Co nclusions: Binocular vision contributes to the precise localization of a pitched baseball, and one eye influences baseball hitting more than the other eye. The motion-in-depth channel (baseball hitting) shares a sensitivity to unequal binocular illumination with the sideways-moti on channel (Pulfrich phenomenon). The timing of the impulses conducted from the eyes appears to be critical for the precise localization of objects processed by either the motion-in-depth (baseball hitting) or the sideways-motion (Pulfrich phenomenon) channels.