Illusory contour figures are perceived as occluding surfaces by 8-month-old infants

Infants have been demonstrated to be able to perceive illusory contours in Kanizsa figures. This study tested whether they also perceive these illusory figures as having the properties of real objects, such as depth and capability of occluding other objects. Eight- and five-month-old infants were presented with scenes that included a Kanizsa square and further depth cues provided by the deletion and accretion pattern of a moving duck. The 8-month-old infants looked significantly longer at the scene when the two types of occlusion cues were inconsistent than when they were consistent with each other, which provides evidence that they interpreted the Kanizsa square as a depth cue. In contrast, 5-month-olds did not show this difference. This finding demonstrates that 8-month-olds perceive the figure formed by the illusory contours as having properties of a real object that can act as an occluder.