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Timothy Sweeny, Steve Haroz, David Whitney; Just walk away: Reference repulsion in the perception of crowd behavior. Journal of Vision 2012;12(9):463. doi: https://doi.org/10.1167/12.9.463.
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© ARVO (1962-2015); The Authors (2016-present)
Humans often behave in crowds, and as such, perceiving crowds may be important for typical social interaction. Perceiving crowds headed toward one’s self may be especially important, so much so that the visual system may devote extra resources for this purpose. If this hypothesis were true, humans should show increased sensitivity for perceiving oncoming headings. Furthermore, as a result of this sensitivity, humans should experience a repulsive perceptual effect around the categorical boundary of leftward/rightward oncoming motion. We tested these predictions and found evidence for both. First, observers were especially sensitive to the heading of an oncoming crowd (or an individual); estimates of a crowd’s heading were more precise near the category boundary of leftward/rightward motion. Second, we found a strong repulsion effect around the category boundary; a crowd walking approximately toward the observer was perceived as being repelled away from straight ahead (e.g., a crowd heading 5º to the left of an oncoming heading was perceived as heading 10º to the left). This repulsive effect was especially strong for crowds, particularly those with variability in the headings of individuals. This latter effect is predicted by narrowed heading tuning near the category boundary. Further experiments showed that the repulsion effect requires integration of both local motion and human form, suggesting an origin in high-level stages of visual processing. Repelling a crowd’s heading away from the leftward/rightward boundary may be important for avoiding head-on collisions. Similar repulsive effects may underlie categorical perception with other social features. Overall, our results show that crowds of walkers are categorically perceived, with improved sensitivity at the category boundary and a concomitant repulsion effect.
Meeting abstract presented at VSS 2012
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