Binocular Depth Perception

Abstract

Successfully negotiating any spatial environment requires two distinct but related forms of visual information. The first is absolute distance information, which allows an animal to “know” its position with respect to other objects or points in space (e.g. D in Fig. 3.1). This is sometimes referred to as egocentric (self-centred) distance perception. It allows visual information to be used for precise motor action. The second form of spatial perception, depth perception, provides information regarding the relative position of two or more objects (e.g. d in Fig. 3.1). It is distinct from absolute distance perception in that it gives no information regarding the distance of the comparison points from the observer. What then is its use? It is argued in this chapter that such relative distance or depth perception is essential for complex object detection, but can only be used to guide reaching motor movements in the limiting case where one of the reference points (e.g. F or P in Fig. 3.1) is always at some predetermined absolute distance.