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Avesh Raghunandan, Shawn Andrus, Laura Nennig; Binocular Capture: The effects of mismatched Spatial frequency and opposite contrast polarity. Journal of Vision 2010;10(7):368. doi: 10.1167/10.7.368.
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© ARVO (1962-2015); The Authors (2016-present)
Background: Binocular capture occurs when the perceived positions of monocular targets are biased by the cyclopean visual direction of surrounding binocular targets. This effect is larger when the vertical separation between monocular targets exceed the spatial period of its carrier frequency. In an attempt to further elucidate the underlying mechanism mediating this effect, we measured the effects of mismatched spatial frequency targets and opposite contrast targets on the magnitude of binocular capture. Methods: Relative alignment thresholds and bias were measured separately for a pair of vertically separated (8, 30, 60 arcmin.) monocular (4′ × 66′) Vernier spatial frequency (SF) ribbons and a pair of monocular (4′ × 66′) Gaussian bars presented across a cyclopean random dot depth edge (10 arcmin. relative horizontal disparity). Each ribbon of the pair comprised carrier frequencies that were either matched (8 cpd and 1 cpd) or mismatched (top ribbon 1 cpd, bottom ribbon 8 cpd, and vice versa). The Gaussian bars were presented with either matched contrast (bright/bright) or opposite polarity (bright/dark) contrast. Gaussian bars were presented at approximately 3.4 times their contrast detection thresholds. Results: Capture magnitudes increased significantly with vertical separation for the matched 8cpd and mismatched SF ribbons, however, the matched 1 cpd ribbons failed to show a significant effect of separation on capture magnitude. Both matched and opposite polarity Gaussian bars produced increasing capture with increasing vertical separation, however the magnitude of capture was significantly larger for the opposite polarity bars. Capture magnitudes exhibited a strong linear dependence on the alignment thresholds for all conditions, but a weak dependence on the alignment thresholds for the matched 1 cpd condition. Conclusions: Stimuli that favor the recruitment of non-linear position mechanisms exhibit greater susceptibility to binocular capture. In these cases the magnitude of capture is strongly dependent on the precision of relative alignment.
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