Binocular Disparity and the Perception of Depth

We perceive the world in three-dimensions even though the input to our visual system, the images projected onto our two retinas, has only two spatial dimensions. How is this accomplished? It is well known that the visual system can infer the third dimension, depth, from a variety of visual cues in the retinal images. One such cue is binocular disparity, the positional difference between the two retinal projections of a given point in space (Figure 1). This positional difference results from the fact that the two eyes are laterally separated and therefore see the world from two slightly different vantage points.