Abstract
The Craik-O’Brien-Cornsweet (COC) effect demonstrates that perceived lightness depends not only on the retinal input at corresponding visual areas but also on distal retinal inputs. In the COC effect, the central edge of an opposing pair of luminance gradients (COC edge) makes adjoining regions with identical luminance appear to be different. To investigate the underlying mechanisms of the effect, we examined whether the subjective awareness of the COC edge is necessary for the generation of the effect. We manipulated the visibility of the COC edge using visual backward masking and continuous flash suppression while monitoring subjective reports regarding online percepts and aftereffects of adaptation. Psychophysical results showed that the online percept of the COC effect nearly vanishes in conditions where the COC edge is rendered invisible. On the other hand, the results of adaptation experiments showed that the COC edge is still processed at the early stage even under the perceptual suppression. These results suggest that processing of the COC edge at the early stage is not sufficient for generating the COC effect, and that subjective awareness of the COC edge is necessary.
Highlights
The perception of lightness is a fundamental aspect of vision, and it depends on the retinal input at the corresponding visual area and on the distal retinal inputs (e.g., Gilchrist, 1977; Adelson, 1993)
Our results demonstrate that the COC effect almost completely vanished in both conditions (BM and continuous flash suppression (CFS)) when the COC edge was invisible (The results in CFS experiment agree with the observation in Supplemental Data of Boyaci et al, 2007)
The post hoc comparison (Ryan’s method, significant level = 0.05) showed that the value in the COC condition was significantly higher than those in the Mask and No-COC condition, and that there was no significant difference between the Mask condition and No-COC conditions. These results demonstrated that when the percept of the COC edge was suppressed by a backward masking (BM) stimulus, the COC effect was reduced to the identical level where the COC edge was physically covered
Summary
The perception of lightness is a fundamental aspect of vision, and it depends on the retinal input at the corresponding visual area and on the distal retinal inputs (e.g., Gilchrist, 1977; Adelson, 1993). On the other hand, regarding psychophysical studies, it was suggested that the COC effect is influenced by higher-stage processing of planar surface attributes (Knill and Kersten, 1991), most of the studies have been performed only by modulating the physical features of the COC edge, such as luminance contrast, spatial frequency, and direction, which were assumed to be processed at the early stage of human visual system (Grossberg and Todorovic, 1988; Paradiso and Nakayama, 1991; Davey et al, 1998; Devinck et al, 2007; Perna and Morrone, 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
