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Peter Veto, Wolfgang Einhäuser, Nikolaus Troje; Biological motion distorts size perception. Journal of Vision 2016;16(12):282. doi: https://doi.org/10.1167/16.12.282.
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© ARVO (1962-2015); The Authors (2016-present)
Size perception is distorted in several illusions, including some that rely on complex social attributes: for example, people of higher subjective importance are associated with larger size. Biological motion receives preferential visual processing over non-biological motion with similar low-level properties, a difference presumably related to a stimulus' ecological importance. Hence, we asked whether biological motion perception can also lead to size illusions. In each trial, observers (N=16) were simultaneously exposed to an upright and an inverted point-light walker from a frontal view for 250 ms. After disappearance of the walkers, two circles were flashed at their positions. The circles differed in size to varying degrees, and observers were queried to indicate with a non-speeded button press, which of the circles appeared larger. We conducted paired sample t-tests on the parameters of the psychometric curves fitted to response frequencies for upright versus inverted cued targets. We found that the circle at the location of the upright walker was perceived smaller than the circle at the location of the inverted walker (t(15) = 2.37, p < .05). Our findings introduce a novel illusion: biological motion reduces subsequently perceived size relative to non-biological motion.
Meeting abstract presented at VSS 2016
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