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Jingping Xu, Zijiang J. He, Teng Leng Ooi; On the contribution of second-order boundary contour strength to binocular rivalry. Journal of Vision 2006;6(6):851. doi: 10.1167/6.6.851.
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© ARVO (1962-2015); The Authors (2016-present)
The alternation frequency of competing images in binocular rivalry is affected by their boundary contours. When one eye views a vertical grating disk(SF=5cpd, diameter=1.25deg, contrast=86%) surrounded by a horizontal grating background(7.5x7.5deg) and the fellow eye views only the horizontal grating background, the observer perceives the vertical grating disk almost continuously despite the corresponding retinal area receiving a horizontal grating. This is because only the vertical grating owns the boundary contour that defines the disk (Ooi & He, 2005). We modified the abovementioned rivalry display by inserting a relative spatial phase shift(0–180deg) in a circular/disk area within the horizontal grating in the fellow eye that corresponded with the vertical grating disk. This allowed us to investigate how rivalry is affected by second-order boundary contours. We found: (i) Increasing the relative spatial phase to strengthen the second-order boundary contour of the horizontal grating disk decreased the predominance and dominance duration of perceiving the vertical grating disk. (ii) The competing images had about the same predominance when the relative spatial phase was about 108deg or larger. Together, these suggest that second-order contours behave qualitatively similar to first-order contours. (iii) When the boundary contour of the horizontal disk was weak, the dominance duration of the vertical grating disk was longest at rivalry onset and decreased at longer rivalry observation interval. This reveals a novel adaptation effect, which was masked when the boundary contour strengths of competing images were about equal. A similar adaptation occurred with prior exposure to a monocular display.
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