Abstract
Mental retardation is typically associated with substantial delays in language. Researchers have been interested in the possible differences in the extent or nature of these delays across genetic syndromes, such as fragile X, Down, and Williams syndromes. This article addresses how genetic factors and environmental characteristics interact to produce specific language outcomes. We suggest that episodes of joint attention provide a means by which genetic anomalies can have indirect effects on some facets of language development. In doing so, we explain the nature of indirect effects and their influence on development; illustrate the link between joint attention and later language ability; discuss how joint attention may account for the characteristics associated with genetic syndromes, with special attention on fragile X syndrome; and consider implications for intervention.