Best Visual Illusion of the Year

The Vision Sciences Society has announced the winner of their annual Visual Illusion of the Year award. This year's top entry demonstrates why baseball players perceive a curveball to "break" when it enters their peripheral vision (as it nears the plate). From the illusion designer's explanation:

The spinning of the curveball creates both a physical effect (“the curve”) and a perceptual puzzle. The curve arises because the ball’s rotation creates an imbalance of forces on different sides of the ball, which leads to a substantial deflection in the path of the ball. The perceptual puzzle arises because the deflection of the ball should appear gradual, but from the point of view of the batter standing near home plate, the flight of the ball often appears to undergo a dramatic and nearly discontinuous shift in position (this sudden shift is referred to as the curveball’s “break”).

As I can't post any of the illusions themselves on this blog, here's a related video of 10 classic optical illusions in 2 minutes.