Sensitivity to binocular depth information in infants

In order to study infants' sensitivity to binocular information for depth, 11 infants, 20 to 26 weeks of age, were presented with real and stereoscopically projected virtual objects at three distances, and the infants' reaching behavior was videotaped. When the virtual object was positioned out of reach, infants tended to lean further forward and to reach less frequently than when the virtual object was positioned within reach. In addition, the proportion of reaches in which the infants patted, closed their hands, or brought their hands together was greater when the virtual object was within reach. However, no difference in the terminal location of the infants' reaches was found as a function of the virtual object's position. Examination of reaches to a near real object revealed that infants frequently did not contact the object or show appropriate hand shape or orientation. The effectiveness of the cue of retinal size and of binocular information for the depth of an object is discussed. It is concluded that 5-month-old infants are sensitive to binocular information for depth.