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Contextual illusions reveal the limit of unconscious visual processing

Harris, Julia J., Schwarzkopf, D. Samuel, Song, Chen, Bahrami, Bahador and Rees, Geraint 2011. Contextual illusions reveal the limit of unconscious visual processing. Psychological Science 22 (3) , pp. 399-405. 10.1177/0956797611399293

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The perception of even the most elementary features of the visual environment depends strongly on their spatial context. In the study reported here, we asked at what level of abstraction such effects require conscious processing of the context. We compared two visual illusions that alter subjective judgments of brightness: the simultaneous brightness contrast illusion, in which two circles of identical physical brightness appear different because of different surround luminance, and the Kanizsa triangle illusion, which occurs when the visual system extrapolates a surface without actual physical stimulation. We used a novel interocular masking technique that allowed us to selectively render only the context invisible. Simultaneous brightness contrast persisted even when the surround was masked from awareness. In contrast, participants did not experience illusory contours when the inducing context was masked. Our findings show that invisible context is resolvable by low-level processes involved in surface-brightness perception, but not by high-level processes that assign surface borders through perceptual completion.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Cardiff University Brain Research Imaging Centre (CUBRIC)
Publisher: SAGE Publications
ISSN: 0956-7976
Date of First Compliant Deposit: 19 November 2017
Date of Acceptance: 21 October 2010
Last Modified: 03 Apr 2019 09:39

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