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Rob Gray, David M. Regan; Unconfounding the time to passage, direction of motion and rotation rate of an approaching object: Different early visual processing in expert baseball players and nonplayers. Journal of Vision 2006;6(6):633. doi: 10.1167/6.6.633.
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© ARVO (1962-2015); The Authors (2016-present)
Observers were presented with a set of 216 simulated approaching textured baseballs in random order. Each had a different combination of time to passage (TTP), direction of motion in depth (dMID), and rate of ball rotation (RR). When required to discriminate TTP, dMID and RR in separate blocks (Expt 1), observers could not discriminate dMID independently of variations in TTP but instead showed a bias towards perceiving objects approaching on a trajectory close to the nose as having a shorter TTP than objects approaching on a trajectory that would miss the face. Judgments of dMID were affected by variations in RR and rotation direction: for simulated overspin the (i.e. the top of the ball spins towards the observer) perceived ball trajectory was biased towards the ground whereas for simulated underspin the perceived ball trajectory was biased towards the sky. RR could be discriminated independently of both TTP and dMID. When required to make all three of these judgments simultaneously on each trial (Expt. 2) discrimination thresholds were not significantly different from those found in Expt. 1. Judgments by expert (college) baseball players (Expt. 3) showed an interaction between TTP and RR (balls with overspin were judged to have a longer TTP) that was not found for non-players. We conclude that information about TTP, dMID and RR are processed in parallel but not completely independently within the human visual system and that the degree of independence can be influenced by sports experience.
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