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The perceptual illusion of baseball's rising fastball and breaking curveball.

1993; American Psychological Association; Volume: 19; Issue: 1 Linguagem: Inglês

10.1037/0096-1523.19.1.3

1939-1277

A. Terry Bahill, William J. Karnavas,

Music Technology and Sound Studies

The rising fastball and the breaking curveball are impossible according to principles of physics and physiology, yet many baseball players claim they exist. The simulation and model presented suggest that the rising fastball and breaking curveball are perceptual illusions caused by the batter misestimating the speed of the pitch. This model uses signals from known primary visual processes only. This model was enhanced by adding an acceleration term. The enhanced model more accurately predicts the position of the ball when it crosses the plate. These models are compared and contrasted to models by McBeath and Bootsma. Sensitivity analyses have shown that the model and simulation are robust with respect to their parameter values. The model is most sensitive to the estimated distance to the ball, and the simulation is most sensitive to the estimated speed of the pitch. According to principles of physics and physiology, a rising fastball is impossible. Yet most batters claim it exists; they say the ball sometimes jumps a foot, right in front of home plate, causing the ball to hop over their bat. Our simulation and model explain this contradiction. Although the numbers given in this article are for professional baseball players, the simulation and model apply to all players, right down to Little Leaguers. They can also be extended to cricket. The rising fastball could be defined as a pitch where the ball (a) jumps up, right in front of the plate, (b) crosses the plate above the pitcher's release point, (c) is going upward when it crosses the plate, or (d) falls less than would be expected due to gravity. By Definitions (b) and (c), a rising fastball could be thrown by a sidearm baseball pitcher or a softball pitcher, but not by an overhand baseball pitcher. For example, an overhand pitch is released about 6 ft (1.83 m) above the ground; if the ball crossed the plate higher than this it would not be a strike. And for the ball to be going upward when it crosses the plate, it would have to fall initially, and then near the end of its flight, experience an upward force that is greater than that of gravity. A force that opposes gravity is produced by the backspin on a fastball. However, the maximum spin rate ever measured for a human pitch, 2,300 revolutions per minute (rpm), would create a force only two thirds that of gravity (Watts & Bahill, 1990). So, although a fastball's lift from backspin may not