Abstract
Aim: Previous studies have shown that under certain conditions the perceived contrast of a dichoptic mixture of two different luminance contrasts is similar to that of the larger of the two contrasts when presented binocularly, a scenario termed winner-take-all. We ask whether dichoptic mixtures of different colour (chromatic) contrast obey winner-take-all, or instead obey the alternative scenario of averaging, in which the perceived contrast of the dichoptic mix is the average of the two contrasts. We also consider the effect of adding task-irrelevant luminance contrast to the dichoptic colour contrast mixtures. Methods: Subjects adjusted the contrast of a disk in one eye that was dichoptically superimposed on a test disk of fixed contrast in the other eye, until the perceived contrast of the mixture equalled that of a separate, fixed-in-contrast reference disk presented binocularly. Results: For isoluminant red, cyan, violet and lime disks the settings were close to winner-take-all. However, when a fixed amount of luminance contrast was added equally to all disks, i.e. was task-irrelevant, the settings shifted significantly towards averaging. Conclusion: The shift away from winner-take-all towards averaging caused by task-irrelevant luminance contrast is consistent with reduced interocular suppression between the different dichoptic colour contrasts, and constitutes a new form of interaction between colour and luminance contrast in binocular vision.
Meeting abstract presented at VSS 2014