Six-month-old infants use motion parallax to direct reaching in depth.

Recent research shows that young infants are sensitive to motion parallax in visual displays but leaves open the question of whether infants use the information to perceive spatial layout. In this experiment, 6-month-old infants were translated horizontally in front of two objects that were yoked to the infant's movement. One object moved in the same direction as the motion of the infant and the other object moved in the opposite direction. This event provided motion parallax information that the object that moved in the opposite direction was nearer in depth. Infants who viewed the display monocularly reached preferentially to the object that was apparently nearer. A control group of infants who viewed the display binocularly showed no such preference. These results provide the first direct evidence that young infants use the spatial information provided by motion parallax to perceive the relative distance of objects and to direct their actions accordingly.