 |
| (Credit: iStockphoto/Barry Howell) |
Curveballs curve and fastballs go really fast, but new research suggests that no pitcher can make a curveball "break" or a fastball "rise." Led by Arthur Shapiro of American University and Zhong-Lin Lu of the University of Southern California, the researchers explain the illusion of the curveball's break in a publicly available study in the journal
PLoS ONE.
The study comes a year after the same group won the prize for best illusion at the Vision Sciences annual meeting with a demonstration of how an object falling in a straight line can seem to change direction. That demonstration led to debates among baseball fans over the existence of the break in curveballs, breaking balls and sliders.
There is no debate in the researchers' minds.
"The curveball does curve, but the curve has been measured and shown to be gradual," Shapiro said. "It's always going to follow a parabolic path. But from a hitter's point of view, an approaching ball can appear to break, drop or do a whole range of unusual behaviors."
A little terminology: to many batters and pitchers, a break is a deviation from the relatively straight path of a fastball. In that sense, all curveballs break. The authors of the study use the term to describe an apparent sudden drop or other change in trajectory as the ball nears home plate. That, they say, is an illusion.
The
PLoS ONE study explains the illusion and relates the perceived size of the break to the shifting of the batter's eye between central and peripheral vision.
"If the batter takes his eye off the ball by 10 degrees, the size of the break is about one foot," Lu said.
He explained that batters tend to switch from central to peripheral vision when the ball is about 20 feet away, or two-thirds of the way to home plate. The eye's peripheral vision lacks the ability to separate the motions of the spinning ball, Lu said. In particular, it gets confused by the combination of the ball's velocity and spin.