The aim of our research is to understand development—the way in which different types of experience effect change during normal development, how those changes are constrained by the biology of the organism, the way in which the nervous system is able to recover from some perturbations, and the limits to plasticity. To examine these questions about development, we study visual perception, both its development in children with normal eyes and its alteration in children with a history of visual deprivation from cataracts.
The normal development of perception. We are investigating developmental changes involving visual capabilities mediated at different levels of the visual pathway: sensitivity to orientation and local motion, which are mediated mainly by the geniculatestriate pathway; integration of local elements into a global percept of form and a global direction of motion, which involve additional processing in extrastriate cortex; the perception of faces, which involves specialized mechansims in the temporal cortex; and the integration of the senses beyond the visual pathway. By using marker tasks for different parts of the visual pathway, we make inferences from the behavioural pattern about the developing nervous system, and we have recently began to test those inferences using event-related potentials and functional Magnetic Resonance Imaging. Our studies indicate that some capabilities are present during the first hour after birth, but that others, such as expertise in identifying faces, take more than 14 years to become adultlike.
The visual development of children treated for cataracts. At The Hospital for Sick Children in Toronto, we are studying the visual development of children who were deprived of normal visual input until they had surgery to remove dense central cataracts and were fitted with contact lenses. These children allow us to evaluate the effects of visual deprivation on development, including the influence of its timing and duration. We are following over 100 children, the largest research population of this type in the world. Studies in progress involve sensitivity to orientation and local motion, the perception of biological motion, and the perception of faces. We are also studying the neural basis of recovery from visual deprivation using event-related potentials and functional Magnetic Resonance Imaging.
The psychobiological roots of aesthetics. We normally assume that adults' judgments of beauty are based on cultural stereotypes. Yet 2-month-old infants look longer at a face rated attractive by adults than at a face rated unattractive. Findings like these suggest that some of adults' preferences are rooted in the way the human nervous system works. We are conducting developmental and cross-cultural studies to identity the nature of the biological constraint.