Abstract
Aim. Dichoptic masking refers to the increase in thresholds for detecting a target in one eye caused by a mask in the other eye. Here we examine the influence of binocular luminance contrast, i.e. luminance contrast that is presented equally to both eyes, on dichoptic masking between a chromatic target and a chromatic mask. Methods. Subjects were required to detect a violet disk on an isoluminant grey background in the presence or absence of a high contrast violet mask. Mask and test were either presented to both eyes (binocular condition), or to opposite eyes (dichoptic condition). All thresholds were measured with various amounts of added, binocular luminance contrast. Results. When both target and mask were presented to both eyes (binocular condition) the addition of luminance contrast had little effect on target detection thresholds in either the target-alone or target-plus-mask conditions. However when the mask was presented to one eye and the target to the other (dichoptic condition), target-plus-mask thresholds were systematically reduced by the addition of binocular luminance contrast in two out of three observers, even though the target-alone condition was little effected by luminance contrast. A control experiment showed that the reduction in chromatic masking from added luminance contrast only occurred when the luminance and chromatic contrasts were spatially contiguous. Conclusion: Binocular luminance contrast can significantly reduce chromatic dichoptic masking. The effect of the luminance contrast appears to be to reduce the interocular suppression between chromatic mask and target.
Meeting abstract presented at VSS 2014