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Emily Slezak, Steven K Shevell; Grouping dichoptically-produced plaids: Ruling out changes in interocular suppression as an explanation. Journal of Vision 2020;20(11):200. doi: https://doi.org/10.1167/jov.20.11.200.
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© ARVO (1962-2015); The Authors (2016-present)
PURPOSE: Observers viewing dichoptic stimuli typically perceive alternations between each eye’s stimulus. Sometimes, however, both eyes’ images are perceived simultaneously. For example, observers can perceive a plaid from superimposing orthogonally oriented gratings from each eye (Liu et al. VR 1992). Further, if two sets of such gratings are presented together, one set above fixation and the other below, observers perceive both as plaid simultaneously above chance (p<0.05; Slezak et al. JOV 2019), suggesting a grouping mechanism acting on binocularly-integrated representations of plaid; an alternative, however, is overall inhibition of interocular suppression. Two experiments rule out  global inhibition of interocular suppression across the entire visual field and  inhibition of interocular suppression in one part of the visual field inducing inhibition in another part. METHODS: For , two different dichoptic images were presented (rivalrous gratings as before and, separately, rivalrous radial lines and concentric rings), matched in spatial frequency and chromaticity but not in superimposed pattern. The experiment measured when both appeared superimposed. For , two different dichoptic gratings known to produce different durations of plaid percepts were presented together. The experiment measured whether the incidence of plaid differed when they were presented together compared to each alone. RESULTS/CONCLUSIONS: The different fused percepts from  were never perceived simultaneously more often than chance, which is not in accord with global inhibition of interocular suppression. In , the presence of a second set of dichoptic gratings never significantly increased the amount of time plaid was seen compared to when one set was presented alone; this is not what’s predicted by inhibition of interocular suppression in one area driving another. Overall, there is no evidence to support inhibition of interocular suppression as the cause for seeing two plaids simultaneously, adding support for a grouping mechanism that acts on binocularly-integrated plaid representations.
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