Development in the understanding of perception: The decline of extramission perception beliefs.

Ancient philosophers, including Plato, Euclid, and Ptolemy, believed in an extramission theory of visual perception, which held that there are emissions from the eyes during the act of vision. Three studies, comparing college and elementary school students, documented a decrease over age in the belief of emissions from the eye during the act of vision and an increase in the belief that vision involved only incoming information. Questions about hearing and smelling were less difficult than those on vision but yielded analogous age trends. The results have implications for cognitive theories of development, for education, and for understanding the child's concept of mind