Please use this identifier to cite or link to this item: http://hdl.handle.net/1893/20534
Appears in Collections:Psychology Journal Articles
Peer Review Status: Refereed
Title: Curvature coding in illusory contours
Authors: Gheorghiu, Elena
Kingdom, Frederick A A
Sull, Manpreet
Wells, Samantha
Contact Email: elena.gheorghiu@stir.ac.uk
Keywords: Illusory contours
Curvature
Adaptation
After-effect
Polarity
Scale
Orientation
Issue Date: Oct-2009
Publisher: Elsevier
Citation: Gheorghiu E, Kingdom FAA, Sull M & Wells S (2009) Curvature coding in illusory contours, Vision Research, 49 (20), pp. 2518-2530.
Abstract: We have employed the shape frequency and shape-amplitude after-effects (SFAE and SAAE) to investigate: (i) whether the shapes of illusory and real curves are processed by the same or different mechanisms, and (ii) the carrier-tuning properties of illusory curvature mechanisms. The SFAE and SAAE are the phenomena in which adaptation to a sinusoidal-shaped contour results in a shift in, respectively, the perceived shape-frequency and perceived shape-amplitude of a test contour in a direction away from that of the adapting stimulus. Both after-effects are believed to be mediated by mechanisms sensitive to curvature (Gheorghiu and Kingdom, 2007a and Gheorghiu and Kingdom, 2009; see also Hancock & Peirce, 2008). We observed both shape after-effects in sinusoidally-shaped illusory contours defined by phase-shifted line-grating carriers. We tested whether illusory and real contours were mediated by the same or different mechanisms by comparing same adaptor-and-test with different adaptor-and-test combinations of real and illusory contours. Real contour adaptors produced after-effects in illusory contour tests that were as great as, or even greater than those produced by illusory contour adaptors. However, illusory contour adaptors produced much weaker after-effects in real contour tests than did real contour adaptors. This asymmetry suggests that illusory contour curves are encoded by a sub-set of mechanisms sensitive to real contour curves. We also examined the carrier-tuning properties of illusory-contour curvature processing using adaptor and test illusory contours that differed in the luminance contrast-polarity, luminance scale and orientation of the carriers. We found no selectivity to any of these dimensions for either even-symmetric or odd-symmetric line-gratings carriers, even though selectivity to these dimensions was found for real contours.
Type: Journal Article
URI: http://hdl.handle.net/1893/20534
DOI Link: http://dx.doi.org/10.1016/j.visres.2009.08.009
Rights: The publisher does not allow this work to be made publicly available in this Repository. Please use the Request a Copy feature at the foot of the Repository record to request a copy directly from the author. You can only request a copy if you wish to use this work for your own research or private study.
Affiliation: Psychology
McGill University
McGill University
McGill University

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