Effects of early visual deprivation on perceptual and cognitive development.

During early infancy, visual capabilities are quite limited. Nevertheless, patterned visual input during this period is necessary for the later development of normal vision for some, but not all, aspects of visual perception. The evidence comes from studies of children who missed early visual input because it was blocked by dense, central cataracts in both eyes. In this article, we review the effects of bilateral congenital cataracts on two aspects of low-level vision--acuity and contrast sensitivity, and on three aspects of higher-level processing of faces. We end by discussing the implications for understanding the developmental mechanisms underlying normal perceptual and cognitive development.