Monocular preferences in binocular viewing.

Faced with an unobstructed view, both foveas can be readily aligned with a distant visual target. The minor difference in the view of the two eyes (which arises from slightly different lines of sight) presents no special problem and is, indeed, the basis of stereopsis. However, when obstructing objects are present in the foreground, the view provided by one eye becomes wholly or partially incompatible with the view of the other. We have investigated how we cope with this everyday situation by having volunteers observe distant targets through a fenestrated screen. In this circumstance, subjects naturally position themselves to view a target of interest with one eye--usually the right eye. This monocular habit in normal viewing reinforces other evidence for the unorthodox idea that visual perception arises from a union in consciousness of monocular images that are elaborated independently.