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Yusuke Nakashima, So Kanazawa, Masami Yamaguchi, Yoichi Sugita; Size-contrast illusion induced by unconscious context. Journal of Vision 2018;18(10):1319. doi: 10.1167/18.10.1319.
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© ARVO (1962-2015); The Authors (2016-present)
The perceived size of objects is influenced by the size of surrounding contextual objects. Little is known about whether such contextual illusions occur even without conscious processing of the contextual stimuli. The present study examined whether the Ebbinghaus illusion can be induced by surrounding contexts that are suppressed from conscious perception. We employed continuous flash suppression (CFS) to render the contextual stimuli invisible. The surrounding contexts were presented to one eye and the high-contrast and dynamic masking stimulus was presented to the other eye. The two test stimuli were presented to both eyes after the presentation of the surrounding contexts and the masking stimulus, and participants judged which of test stimuli appeared larger. Three different inter-stimulus intervals (ISIs) between the inducer and test stimuli were used to examine decay time of the illusion. We also tested the conditions that the surrounding inducers were visible and not presented. The size-contrast illusion was observed even when the inducers were rendered invisible, although the effect was weak―approximately one third the strength of that induced by visible contexts. The effects induced by both visible and invisible contexts decayed with equal speed as the ISI between the inducer and test stimuli increased. Previous findings have shown that stimuli suppressed by CFS are still processed in V1, but not in the higher visual areas. Our results suggest that the size-contrast effect in the Ebbinghaus illusion is mediated in V1, and the monocular pathway in V1 is involved in the unconscious effect.
Meeting abstract presented at VSS 2018
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