Abstract
INTRODUCTION & PURPOSE: Chromatic interocular-switch rivalry (CISR) occurs when two equiluminant but chromatically rivalrous stimuli (e.g., one “purple” and one “green” circle) are presented separately to each eye, and then swapped interocularly several times a second (e.g., 3.75Hz). Instead of seeing the fused circle change color rapidly, the percept is a long-lasting color that alternates between the two presented chromaticities (Christiansen, D’Antona & Shevell, VSS2014). This study investigated whether object-level grouping contributes to the resolution of CISR when two separate rivalrous circles, one above the other, are viewed simultaneously. If so, then the probability of simultaneously perceiving two spatially separated circles having the same color would be greater than predicted from the independent probabilities of perceiving each circle of that color. METHODS: At each moment, two spatially homogeneous circles (one above fixation, one below) were presented to each eye at corresponding retinal locations. Each circle alternated over time between two equiluminant chromaticities along one of the cardinal color direction (either L/(L+M) or S/(L+M)). The time-average chromaticity was always equal-energy-spectrum (EES) “white”. To determine the independent probabilities, percepts were measured during CISR with one spatially homogeneous circle in each eye (either above fixation or below, in separate runs). The task always was to report (via a gamepad) the color of the top circle and/or the bottom circle in the fused binocular percept. In separate runs, three different square-wave frequencies were tested: 3.13, 3.75 and 4.69Hz. RESULTS & CONCLUSIONS: The probability of simultaneously perceiving two circles of the same color was far greater than predicted from the independent probabilities of perceiving each circle alone with that color (p< 0.01 for each of 3 observers at each of the 3 temporal frequencies). Therefore, object-level grouping contributes to resolving chromatic interocular-switch rivalry. This influence from perceptual organization is a novel aspect of interocular-switch rivalry.
Meeting abstract presented at VSS 2015