Development of shadow perception in hve-andsevenmonth-old infants

Purpose: The goal of this investigation is to describe the development of the ability to decompose the retinal image into a set of intrinsic images that capture the scene characteristics of reflectance, illumination and orientation. We investigated the ability of 5- and 7- month-olds to distinguish between a light surface in a dark shadow and dark surface in bright light Method: Duration of looking was used lo measure this ability. We habituated infants to a cube mounted in the cenler of a dark screen. The cube was illuminated by a slide projector such that it could be presented either bisected by shadow 01 entirely in bright light. Two cubes were also created. One cube was half whit : and black while the other was all white. During habituation, the half black and half white cube was presented with a shadow bisecting it such that four quadrants wre generated. One quadrant was painted white and in bright illumination, a sec >nd quadrant was white and in shadow, a third quadrant was painted black and n bright illumination while the fourth was black and in shadow. The black quadrmt in bright light and the white quadrant in shadow were made to match in lum-nance. After the habituation criterion was reached, 6 test trials were presented. Test trials consisted of the black and white cube with the shadow removed and the white cube with the shadow unchanged but with the gray surface removed. Additi jnal subjects were run in a control study to provide baseline measures of the attention-holding properties of the two tesl displays. Results: In an preliminary study, adults tended not to notice a change in the location of the shadow, but the) did notice the change in the reflectance of half of the cube when a black and whitr cube was replaced with an all white cube. Seven-month-old infants also provide! statistically significant evidence that they ignored the shadow in that they looked longer at the test display thai changed in reflectance than at the test display in which the shadow was removed. Five-montholds provided no such evidence. Conclusion: The ability to discriminate between shadows and dark surfaces and a degree of lightness constancy develops al about 6 months of age in human infants.