Newell, Best, Gastgeb, Rump, and Strauss Categorization and Autism 1 Chapter x The Development of Categorization and Facial Knowledge: Implications for the Study of Autism Lisa C. Newell, Catherine A. Best, Holly Gastgeb, Keiran M. Rump & Mark S. Strauss Autism is a pervasive developmental disorder with onset before the age of three years. Recent studies suggest that its prevalence in the United States is as high as 1 out of every 150 children (Centers for Disease Control and Prevention, 2007), and there is concern that the incidence of autism is rising world-wide (Chakrabarti & Fombonne, 2005). There has been a tremendous amount of research on autism, especially in recent years. However, the theories which attempt to explain autism have failed to address how autism might develop before the diagnosis occurs (i.e., the development of autism during infancy). In addition, there is little theoretical explanation of the development of the diagnostic symptoms of autism. Despite the lack of scientific insight into the early development of autism, there is a growing body of evidence that symptoms of autism are present before the first birthday. The intervention literature has suggested that early intervention is most effective at altering the course of the disorder. Thus, there is a pressing need to diagnosis autism before age two. Research findings from our lab indicate a number of cognitive deficits in individuals with autism that are developing during infancy for typically developing individuals (e.g., gender categorization of faces). We, along with several other labs across the country, are beginning to investigate