Baseball hitting, binocular vision, and the Pulfrich phenomenon
A. J. Hofeldt, F. B. Hoefle and B. Bonafede
Department of Ophthalmology, Harkness Eye Institute, Columbia University, New York, NY, USA. AHofeldt@AOL.COM
OBJECTIVES: To determine if dimming the light to 1 eye affects baseball
hitting (motion-in-depth) and if binocular interaction influences the
ability to hit a baseball. METHODS: The ability to hit baseballs in a
batting cage was measured under conditions of (1) no filter before either
eye, (2) neutral density filters before both eyes, and (3) a neutral
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 no significant
effect on batting ability compared with no filter (87% vs 94%). While
viewing binocularly, a filter before 1 eye caused a significantly greater
reduction in hitting scores than when the filter was placed before the
opposite eye (36% vs 80%). This greater effect of 1 eye on hitting scores
denotes an ocular preference or dominance within the motion stereopsis
system. The eye associated with the greater reduction in hitting ability
when dimmed by a filter was termed the dominant 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 placed before the nondominant eye, the
hitting ability was not significantly reduced (80% vs 87%). The batting
scores decreased as filter densities increased from 0.3- to 0.6-optical
density, and the effect was significantly more for the dominant eye than
for the nondominant eye. CONCLUSIONS: 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-motion 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.
