Motion in depth distorts perceived stereoscopic depth

A number of studies have shown that fronto-parallel motion information can distort the perceived location ofan object. Perceived location is offset in the direction ofmotion. The present study determines whether motion-in-depth information can affect the perceived depth generatedby binocular disparity information. Observers performed adepth discrimination task between two random-dot optic-flow motion patterns that were stereoscopically offsetrelative to each other. The motion simulated was fronto-parallel (all the dots moved vertically upwards ordownwards), or motion in depth, either forward motion (thedots moved radially away from the stimulus centre) orbackwards motion (the dots moved radially in). The resultsshowed that perceived depth was offset in the depth direc-tion simulated by the motion in depth. When taken as awhole, the present and earlier studies show that motion candistort our entire three dimensional representation of space.