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Andrea Christensen, Winfried Ilg, Martin A. Giese; Biological motion detection does not involve an automatic “perspective taking”. Journal of Vision 2011;11(11):743. doi: 10.1167/11.11.743.
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© ARVO (1962-2015); The Authors (2016-present)
Concurrent motor execution influences action perception. Previously, we presented evidence for a spatio-temporal tuning of this action-perception coupling (Christensen et al., JoV, 2009, 9(8)). Facilitatory influences were found only for synchronous and spatially similar actions. Additionally, when observing others, subjects automatically tend to embody another person's visuo-spatial perspective (Thirioux et al., Brain Cogn, 2009. 70(2)). This raises the question, whether the performance increase for spatially congruent stimuli depends on such “disembodied self-locations” and whether a body- or visual-centered frame of reference determines spatial similarity. METHOD: Point-light stimuli of waving arms embedded in a scrambled mask were presented in a detection task. Participants were instructed to interpret the point-light stimuli either as person seen from the front or from behind. The displayed stimulus (right or left arm) matched the executed arm movement either in a visual or in a body-centered frame of reference. The detection thresholds were determined by varying the number of noise dots in the stimuli; compared to a baseline without concurrent execution of motor actions. RESULTS/CONCLUSION: Significant facilitation of biological motion detection by concurrent motor execution was observed only when the visual stimulus matched the executed movement in a visual frame of reference. The instruction to interpret the stimulus in different body-centered perspectives did not influence the results, even if we controlled for subtle kinematic differences between front and back views. We conclude that the modulation of biological motion detection occurs in a visual frame of reference and does not include active perspective taking by the observer.
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