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Luke E. Miller, David Carmel, Ayse P. Saygin; Breaking Bio: Does biological motion have preferential access to awareness?. Journal of Vision 2014;14(10):1018. doi: 10.1167/14.10.1018.
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© ARVO (1962-2015); The Authors (2016-present)
Perceiving biological motion is important for human behaviour and social interaction. Due to its ecological importance, biological motion is believed to be especially salient, but whether and at which stage of processing such "special" treatment occurs is unknown. Here we presented point-light walker (PLW) biological motion stimuli while suppressing them from awareness using continuous flash suppression (CFS). We gradually increased the contrast of the masked stimuli and measured the time it took them to break into awareness (or the contrast needed to breakthrough). To ensure that judgments were orthogonal to the nature of the masked stimuli, subjects reported the location of the PLWs (whether the figure was slightly to the left or right of fixation). In Experiment 1, biological motion stimuli were presented either intact or spatially scrambled, which disrupts the global form of the PLW. We reasoned that faster breakthrough of a stimulus would indicate preferential processing (cf. Yang et al., 2007). Indeed, intact PLWs were perceived 17% faster than their scrambled counterparts. The effect was not due to inherent stimulus differences influencing the target location task since control studies without CFS showed no difference between conditions. In Experiment 2, we manipulated form and motion information in the masked stimuli, presenting intact and spatially scrambled PLWs in upright or inverted orientations. Inversion of intact PLWs reduces global form and disrupts local motion; inversion of scrambled PLWs disrupts both form and local motion. For upright PLWs, we replicated the findings of Experiment 1. We also observed that intact PLWs reached awareness 4% faster when presented upright compared to inverted; no inversion effect was found for scrambled PLWs. Taken together, these studies show preferential processing of biological motion without awareness, and suggest the effect is driven primarily by the coherent form of the stimuli rather than local motion.
Meeting abstract presented at VSS 2014
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