ABSTRACT
Stereopsis relies principally on the extraction of horizontal retinal disparities. As such, we assume that the vertical contours (i.e., horizontal contrast energy) are of principle import for stereopsis. Yet there are theoretical reasons for believing that horizontal contours should be involved in binocular matching (if not stereopsis proper) as well. First, they would facilitate the computation of vertical disparities, which are necessary for the control of disjunctive eye movements and perhaps the computation of absolute depth. Second, the process of binocular matching is a two-dimensional one; its solution requires information along both principle orientations. In this study, we have measured the efficacy with which horizontal or vertical contours can be binocularly matched by measuring thresholds for the detection of interocular correlation for oriented dynamic random-line stereograms. We find that the slopes of the psychometric functions are almost a factor of two steeper when matching vertical contours, indicating a narrower noise distribution along the decision axis associated with these stimuli.
