Visual hemifield dominance during interocular conflict and why it matters

Due to the eyes being separated about six centimeters horizontally, the visual system is often confronted with non-overlapping visual input, especially in the visual periphery. Apart from supporting stereovision, non-overlapping – conflicting – visual input can potentially hinder perception of distant, fixated objects of interest. Here we review, on first sight conflicting, studies on interocular conflict in the visual periphery that reported either nasal or temporal visual field preferences during interocular competition. While these studies interpreted hemifield preferences mainly in terms of neuro-anatomical aspects of the visual system, we here argue that they have a functional goal: to suppress information that hinders perception of distant fixated objects of interest. Optimizing hemifield preferences towards this goal leads to a temporal visual field preference at around fixation, a nasal visual field preference in the near periphery, and a temporal visual advantage in the far periphery. Our functional account of hemifield preference during interocular competition thereby reconciles inconsistencies in the literature by analyzing at what eccentricities the interocular conflict in the studies was evoked. Finally, our proposal once more shows that interocular conflict in general, as well as binocular rivalry specifically, are not merely a laboratory curiosity.