An excerpt from an article that was in GQ about the science of baseball:
Over the next week, Harrison. Bowden, and others will convince me that highly developed binocularity- the coordinated functioning of the eyes. Particularly while they track a moving object –ought to be considered baseball’s “sixth tool.” (Scouts have traditionally emphasized five tools: the abilities to hit for average, to hit for power, to run, to throw the ball, and to field it.) That’s how predictive binocularity is of a hitter’s success, and that’s what the beach-scene eye-card test measures. Can you bear with me for a brief Bill Nye moment? Here goes: Your ability to perceive depth is made possible by the spacing of your eyes, which take in from two slightly different perspectives two separate images of whatever your looking at. When those images meet in the brain, they form a single three- dimensional picture in which you can read both the placement and movement of objects in space. But your eyes only that one point of stereoscopic focus. Outside of it, they see everything in twos, though your brain has learned to suppress this. In effect, the eye card assesses how broad your point of stereoscopic focus is, and among the tiny, self-selected population of world class ballplayers, it can be amazingly broad indeed. Some guys literally cut the eye card in half, Harrison tells me, and free-fuse it at twelve to eighteen inches. Bonds, whose vision is the best among thousands and thousands” of players Harrison has tested, can do so at a distance of four feet. Which is outrageous, and which has nothing to do, by the way, with BALCO. But still, why is binocularity important in baseball? “With less-than-perfect binocularity, the brain will suppress the simple vision of one eye,” Harrison says. “One eye alone is sufficient to see the seams on the ball or trajectory. But a one-eyes hitter has no depth perception.”
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