Scientist Throws Curve Into Breaking-Ball Debate

Contends curveballs are an illusion; ridiculous, says former star major league pitcher

By Peter West
HealthDay Reporter

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FRIDAY, Oct. 30 (HealthDay News) -- The ball flies out of the pitcher's hand. In less than a second, it curves and then drops, baffling the batter.

Or does it?

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The curveball, when thrown correctly, is one of baseball's most daunting pitches. For more than a century, batters great and not so great have sworn that the ball seems to have a life of its own.

But now, a California cognitive neuroscientist has resurrected the timeless debate -- just in time for the Yankees-Phillies World Series showdown -- over whether the curveball is real or, in fact, an optical illusion that does not "break" before the hitter can whack it.

"Physically, there is no such thing as a breaking curveball," said Zhong-Lin Lu, who holds the William M. Keck Chair in Cognitive Neuroscience at the University of Southern California, in Los Angeles. "It's mostly in the hitter's mind."

According to Lu, who helped to design a popular Web animation that illustrates the science behind what he calls the curveball illusion, the ball travels relatively straight toward the batter, curving somewhat but not nearly as much as claimed. What causes the perception of the break is a complex interplay between the fast spin of the ball, the contrast between the ball's red seams and white background, and the batter's flawed visual perception as the ball nears the plate.

Here's how the curveball phenomenon seems to work, said Lu, a visual motion and perception specialist:

The ball leaves the pitcher's arm at approximately 75 mph, slower than an average fastball. While it hurtles toward the batter, the ball spins obliquely at around 1,500 rpm (or 25 rotations per second). The ball reaches the plate in about 0.6 seconds.

Because of its unique spin, the ball appears to be moving faster than it really is, causing the batter to overestimate the speed. A slight curving trajectory forces the ball to move somewhat away from the hitter's frontal view toward his side -- or peripheral -- vision just before he swings.

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