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Sherryse Corrow, Al Yonas, Carl Granrud; The Convexity Assumption: Infants use Knowledge of Objects to Interpret Static Monocular Information by 5 Months. Journal of Vision 2010;10(7):497. doi: 10.1167/10.7.497.
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The adult visual system uses top-down information to interpret ambiguous images. When the 2D contours of a cube are presented to the retina, for example, adults generally perceive a 3D cube. In the absence of information to the contrary, the adult visual system assumes that objects are convex. Our question is, when do infants begin to form and use such assumptions to interpret visual input? We presented a wire half-cube, with its vertex pointed away, to 5- and 7-month-old infants (n = 17 and 20 respectively), and observed the infants' reaching behavior under monocular and binocular viewing conditions. For adults, the cube's vertex appears closer than the outer edges when the display is viewed monocularly; but the cube's actual layout is perceived when viewed binocularly. In the monocular condition, the infants in both age groups reached significantly more often to the central region of the display than to the outer edges (5 months, p=0.009; 7 months, p=0.016). Furthermore, infants reached more often to the center of the display in the monocular condition than the binocular condition (5 months, p<0.0001; 7 months, p=0.016). These results suggest that the infants perceived the cube as convex under monocular viewing conditions and as concave under binocular conditions. By 5 months of age, infants use their knowledge of 3-dimensional objects to interpret ambiguous 2-dimensional displays. This knowledge is provided by mechanisms that recognize a form and supply information, in a top-down fashion, to early visual projection areas. Further work will be needed to investigate this ability in younger infants.
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