September 2015
Volume 15, Issue 12
Vision Sciences Society Annual Meeting Abstract  |   September 2015
How fast can a baseball spin before an observer can’t tell the direction of rotation?
Author Affiliations
  • Arthur Shapiro
    Department of Psychology, American University, Washington D.C.
  • Jonathan Newport
    Department of Physics, American University, Washington D.C.
  • Bree DeVries
    Department of Computer Science, American University, Washington D.C.
Journal of Vision September 2015, Vol.15, 286. doi:
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      Arthur Shapiro, Jonathan Newport, Bree DeVries; How fast can a baseball spin before an observer can’t tell the direction of rotation?. Journal of Vision 2015;15(12):286.

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      © ARVO (1962-2015); The Authors (2016-present)

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In baseball, a pitcher throws a 3” ball toward a batter positioned 60.5 feet away. Shapiro et al (2009, 2011) hypothesized that a batter’s perception of a pitch could be influenced by changes in the ball’s retinal location (i.e., whether the batter views the ball centrally or peripherally). One question concerns whether a curveball spins too fast for a batter to discern the direction of spin. To address this question, we constructed a device in which a microcontroller spins a motor at rates up to 3000 rpm. A baseball rested on a driveshaft extending from the motor; an LCD shutter controlled the presentation duration (set at .6 sec); steady LED lights illuminated the ball. The observer viewed the ball from a distance of 140 cm (ball subtended 3.2 deg) and pressed one of two buttons to indicate the direction of perceived spin. Experiment 1: The ball was presented at rotation rates between 500 and 2500 rpm (40 trials in random order; half the trial were clockwise, half counter clockwise). Experiment 2: Similar set up, but on different sets of trials the observers viewed the ball either centrally or 10 deg in the periphery. Experiment 3: On different sets of trials the ball was positioned on the motor in a “2-seam” or a “4-seam” configuration. For all conditions, at rates up 1200 rpm, observers were typically correct 100% of the time, but near 2000 rpm, observers were typically at chance. Peripheral viewing and spin configuration had little effect on observer’s ability to identify spin direction. Since an MLB curveball spins between 1400 and 1800 rpm, these pitches approach the limit of our perceptual resolution. The minor effect of peripheral viewing and spin configuration suggest, surprisingly, that our ability to perceive spin direction may be mediated by low spatial frequency channels.

Meeting abstract presented at VSS 2015


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