Author:

Keywords:

06 Biological Sciences, 11 Medical and Health Sciences, Ophthalmology & Optometry

Abstract:

Purpose. Much of the currently available evidence about perceived space has been obtained in the laboratory under restricted viewing conditions. Studies in natural environments usually have involved metric relations, typically on a visible ground plane. In contrast, the present study used binocular viewing in a natural terrain at full daylight to evaluate perceived directions among objects at eye level. Method. Observers judged the direction from one object to another, using a radio-controlled pointer. The configuration of the target, pointer, and vantage point was systematically varied, at distances from one to 24 m. Results. Under most conditions, judgments were quite consistent both within and between observers, but relatively large systematic errors occurred in many conditions. Results are interpreted in terms of both curvature of visual space and a nonlinear relation between perceived depth and true range. Conclusions. Visual space is elliptical in near space and changes to hyperbolic in far space. The nexus of visual directions is not necessarily metric, and may have a more primitive structure than conventionally considered.