Abstract
The visual system must employ assumptions, or constraints, to interpret pictorial (static monocular) displays. For example, for the depth cue of relative size to be effective, adults use an assumption that two objects are similar in size in perceiving the retinally larger one as closer. Our goal is to investigate if and when infants, like adults, use similar assumptions to perceive 3-D layout. Last year at VSS, we reported that six-month-old infants use line junctions to perceive a concave shape as convex when only static monocular information is available. In the present study, we investigated whether infants, like adults, use the assumption that faces are convex. Specifically, we used Richard Gregory's concave face illusion to examine if infants use prior knowledge about the 3-D layout of faces to direct their reaching to the apparently closest part of the display (the nose). Methods: Using a within-subjects design, we presented six-month-old infants (n = 11) with Gregory's concave face illusion and observed the trajectory of infants' reaching behavior under monocular and binocular viewing conditions. Reaching behavior was scored by a blind observer. Results: Infants reached more often to the center of the display in the monocular condition (67%) than in the binocular condition (12%, p = 0.001). These results indicate that infants perceived the display as convex under monocular viewing conditions and as concave when viewing the display with two eyes. In addition, in the monocular condition, some infants attempted to grasp the nose of the face. Discussion: These findings suggest that experience with the concave nature of faces may influence how infants respond to this illusion. This provides further evidence that infants use assumptions to perceive the 3-D structure of the environment.
Interdisciplinary Training Program in Cognitive Science, NIH T32 HD007151.