Dr. Arthur G. Shapiro, of the Department of Psychology at Bucknell University (Lewisburg, Pennsylvania), along with Zhong-Lin Lu, Emily Knight and Robert Ennis (University of Southern California, Dartmouth College, and SUNY College of Optimetry, respectively) won the 2009 award for the Best Illusion of the Year at a meeting of the Vision Sciences Society.
The 2009 contest was held on May 10, 2009, at the Naples Philharmonic Center, in Naples, Florida, during the week of the Vision Sciences Society conference.
Their demonstration, called “The break of the curveball,” explains why a baseball pitcher’s curve ball seems to break so much as it is thrown toward a batter.
The physics of a baseball states that it curves because of the topspin put on the ball. It curves gradually during its flight toward the batter’s box by a couple of feet.
However, for a player standing in the batter’s box, it seems to be going straight during the first part of its flight but then jumps several feet, later on, almost instantaneously.
Why does its trajectory appear to change so abruptly to the batter?
The animation provided by the Shapiro team illustrates why the batter sees an abrupt change in the ball.
Page two shows where to find the animation of the Shapiro team.
The Shapiro team animation is shown on the website IllusionContest.
However, when you look at it out of the corner of your eye (looking directly at the blue dot), then it appears to be moving at an angle. When a batter looks at the ball with his or her peripheral vision, it appears to move to the side.
The website states, “In baseball, a curveball creates a physical effect and a perceptual puzzle. The physical effect (the curve) arises because the ball’s rotation leads to a deflection in the ball’s path. The perceptual puzzle arises because the deflection is actually gradual but is often perceived as an abrupt change in direction (the break).”
And, “Our illusions suggest that the perceived “break” may be caused by the transition from the central visual system to the peripheral visual system. Like a curveball, the spinning disks in the illusions appear to abruptly change direction when an observer switches from foveal [central] to peripheral viewing.”
Thus, when the spinning ball is seen moving directly in front of one’s eyes (using our central visual system), it appears to move in a straight line.
However, eventually it is seen out of the corner of one’s eye (using our peripheral visual system), as if standing sideways in the batter’s box, and the spin of the ball makes the ball appear as if it is curving.
Page three talks more about the curveball study, and also provides the other finalists of the contest.
The batter sees the ball leave the pitcher’s fingers with the central system, but as it gets closer to the plate, the peripheral system takes over.
It suddenly jumps. Oftentimes, it’s the ultimate demise of the unwary batter.
Now, that you know what happens, will baseball batters be better able to judge the flight of a curve ball? Mmmm, I wonder?
The top ten finalists of the 2009 Best Illusion of the Year award is found here.
The reasons why the illusion/vision contest is held is explained at "About the Contest."
In part, it states, "The contest is a celebration of the ingenuity and creativity of the world’s premier visual illusion research community. Visual illusions are those perceptual experiences that do not match the physical reality. Our perception of the outside world is generated indirectly by brain mechanisms, and so all visual perception is illusory to some extent. The study of visual illusions is therefore of critical importance to the understanding of the basic mechanisms of sensory perception, as well as to cure many diseases of the visual system."