ABSTRACT
Typical development serves as a standard that can be used to assess the occurrence and severity of deviance and delay in various atypical populations. In turn, the study of atypical development informs our understanding of typical development-for example, by allowing researchers to identify necessary relations among cognitive structures (Cicchetti, 1984; Hodapp & Burack, 1990). One area that well illustrates the mutually beneficial nature of the typical-atypical relation is research on theory of mind-the ability to attribute mental states to oneself and to others (e.g., Astington, 1993). In a seminal article, Baron-Cohen, Leslie, and Frith (1985) reported that high-functioning individuals with autism performed worse than did mental-age-matched individuals with Down Syndrome on a test of theory of mind. A subsequent study (Baron-Cohen, Leslie, & Frith, 1986) reported that the same individuals with autism were impaired on theory-of-mind tasks but not on other types of task, such as a mechanical (physical) causality task in which reasoning about mental states was not required.
