The Impact of Perceptual Organization on the Limits of Binocular Fusion

As a consequence of the separation of the two eyes in the head, the images of objects projected onto the two retinas are in different positions, called binocular disparity. The brain uses this positional information to represent the 3D layout or depth in a scene, a process called stereopsis. The two monocular half-images of objects will be integrated and seen as single if the binocular disparity is within Panums fusional area. Objects with disparities beyond this region will be seen as double. There are likely many factors which influence the perception of diplopia, including cognition (i.e., attention or suppression) or low-level object features (i.e., size). This thesis evaluates the proposal that higher-order visual processing, grouping through uniform connectedness, diminishes the perception of diplopia. To this end, in a series of experiments I presented isolated single elements, pairs of isolated and connected elements, and elements with varying levels of connectedness. Taken together, the results show that connecting elements elevates diplopia thresholds. This result is consistent with both the impact of perceptual organization and the use of larger receptive fields to process the disparity of the object. These two possibilities are discussed along with future experiments designed to distinguish between these accounts.