Depth perception by the active observer.

The connection between perception and action has classically been studied in one direction only: the effect of perception on subsequent action. Although our actions can modify our perceptions externally, by modifying the world or our view of it, it has recently become clear that even without this external feedback the preparation and execution of a variety of motor actions can have an effect on three-dimensional perceptual processes. Here, we review the ways in which an observer's motor actions--locomotion, head and eye movements, and object manipulation--affect his or her perception and representation of three-dimensional objects and space. Allowing observers to act can drastically change the way they perceive the third dimension, as well as how scientists view depth perception.