Abstract
In binocular rivalry produced using orthogonal diagonal gratings, if a matching diagonal grating is added to one eye then rivalry is eliminated. We found that in fact rivalry is not eliminated for certain spatial frequency combinations for matched and rivalrous diagonal patterns involving differences of one octave or more. We investigated whether this effect generalizes to plaids which are the sum of: (1) rivalrous orthogonal diagonal gratings and (2) identical vertical gratings in the two eyes. Over 100 s trials, observers pressed one key when the left grating predominated, or another key when it was not visible. For 2 and 4 cpd patterns, rivalry occurred if the spatial frequency of the vertical gratings was more than 0.4 octaves above or below that for the diagonal gratings (or 0.35 octaves for 8 cpd gratings).
Following these measurements for the bandwidth for rivalry, we investigated the interaction between rivalry and depth. Similar plaids were used, with the additional manipulation that depth was produced in the vertical components using three methods: (1) an orientation disparity of plus or minus 4 degrees was used to produce tilt forwards or backwards; (2) slant was produced using a spatial frequency difference between the two eyes; (3) a phase offset in the vertical grating was used so that the top and bottom of the image were in different depth planes. Observers performed a match for the apparent depth of the vertical components in the plaids using the method of adjustment. In all cases depth and rivalry coexisted when the spatial frequency difference between the vertical and diagonal gratings was greater than 0.8 octaves, but neither depth nor rivalry was present for smaller differences. These results place constraints on models of stereopsis and rivalry.
Supported by an NSERC grant to HRW (#OP227224) and supported in part by a CIHR research training grant in vision health research.