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Ryan Mruczek, Christopher Blair, Kyle Cullen, Kyle Killebrew, Annie Aguizzi, Gideon Caplovitz; The effects of motion dynamics on the Ebbinghaus and Corridor illusions. Journal of Vision 2016;16(12):414. doi: 10.1167/16.12.414.
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© 2017 Association for Research in Vision and Ophthalmology.
We recently demonstrated that image dynamics greatly enhance the Ebbinghaus Illusion (Mruczek et al., 2015 Front Hum Neurosci). We proposed that uncertainty in the representation of a target's angular size is a critical factor in determining the degree to which context influences its perceived size. Here, we extend our investigations of this target-specific 'uncertainty hypothesis' to the Corridor Illusion. The Corridor Illusion is predicated on the notion that the farther of two objects with identical angular sizes must be physically larger, and perceived size is modulated accordingly. Unlike for the Dynamic Ebbinghaus Illusion, the uncertainty hypothesis predicts a weaker effect of context if the target is moving in the context of the Corridor Illusion. Uncertainty as to whether the target maintains a constant angular size as it translates should reduce the need to perceptually correct for changes in perceived distance. To test this hypothesis, we constructed a Dynamic Corridor Illusion in which a target object moves back and forth along the floor of a corridor. Compared to Static versions with matched viewing conditions, we observed increased magnitudes for the Dynamic Ebbinghaus Illusion (replicating our previous findings) and decreased magnitudes for the Dynamic Corridor Illusion (Experiment 1: free-viewing, method of adjustment, Dynamic ~10%, Static ~20%, p = 0.10; Experiment 2: peripheral fixation, method of constant stimuli, Dynamic ~10%, Static ~25%, p < 0.001). Thus uncertainty in the angular size of the target (driven by stimulus dynamics) enhances contextual effects in the Ebbinghaus Illusion, whereas it decreases contextual effects in the Corridor Illusion. These results are inconsistent with a recent model proposing that the Corridor Illusion results from a target-independent, background-induced spatial shift in early visual cortex receptive fields (Ni et al., 2014 Curr Biol). Rather, our results highlight uncertainty-driven weighting of visual cues by neural circuits computing perceived object size.
Meeting abstract presented at VSS 2016
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