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Nikolaus Troje, Morgan Davis; Bootstrapping a prior? Effects of experience on the facing bias in biological motion perception. Journal of Vision 2011;11(11):692. doi: 10.1167/11.11.692.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptually bistable visual stimuli provide an interesting means to study how the visual system turns the generally ambiguous flow of sensory information into a reasonably stable model of the world. Biological motion point-light displays provide a particularly interesting class of stimuli in this respect. Even though the stimulus itself does not contain any information about its orientation in depth, fronto-parallel projections of a point-light walker are preferentially seen as if the walker is facing the viewer rather than facing away. In two different experiments, we show that the degree of this “facing-the-viewer bias” strongly depends on the amount of exposure an observer previously had with point-light displays. We measure the degree of the facing bias by asking observers to indicate the apparent spin (clockwise or counter-clockwise) of a point-light walker – a method insensitive to a potentially confounding response bias. In the first experiment, we compared the degree of the facing bias between na&ıuml;ve observers and graduate students who work with point-light displays on a daily basis. In the second experiment, we exposed initially na&ıuml;ve observers over the course of several weeks systematically to point-light displays and measure the degree of the facing bias before and after this treatment. In both cases, we observe a substantial increase in facing bias with the amount of expertise the observers had with point-light displays. We discuss these results in the context of a process which sharpens prior expectations by means of self-reinforcement in the absence of information that contradicts the developing prior.
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