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Karyn Danatzko, Jeannine Pinto, Maggie Shiffrar; Perceptual learning and point-light human actions. Journal of Vision 2002;2(7):349. doi: 10.1167/2.7.349.
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© ARVO (1962-2015); The Authors (2016-present)
Adults are exquisitely sensitive to human movement, even when its appearance is reduced to a dozen discrete “point-lights.” However, this sensitivity seems to be orientation specific. Why do we readily recognize upright human motion but fail to perceive the same figure when it is inverted? One possibility is that our extensive experience with upright human movement tutors perception. If sensitivity is a function of perceptual learning, it should be possible to improve the recognition of inverted human figures with increased experience.
To provide such experience, we required observers to make judgements about human motion. We created brief video displays of 4 fully-visible actors engaging in each of 4 activities: running, walking, skipping, and marching. We recorded reaction time (RT) and accuracy as participants repeatedly categorized these actions. One-half of the observers were presented inverted displays. For both orientations, RT improved with practice. Sessions continued until RT reached an asymptote (M = 8.0 sessions).
To examine whether visual experience of fully-rendered human movement supports the perception of point-light figures, we created point-light displays of the 4 target activities. Over sessions (M = 8.2), observers repeatedly categorized the actions. If perception of upright point-light displays arises solely from the extraction of motion patterns available in our ordinary visual experience, then we should find that exposure to the fully-visible inverted figures improves observers' perception of inverted point-light actions. When presented point-light displays, observers' initial RTs were again slow. However, all 3 of the observers judging upright displays showed evidence of “savings,” the transfer of perceptual skill from fully-visible to point-light displays. In contrast, only 1 of the 3 observers judging inverted displays showed savings. This failure to improve during the inverted trials suggests other constraints on visual processing. Supported by NEI grant R01 EY12300
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