The present study was designed to evaluate the validity of the false belief task as a measure of theory of mind development in individuals with intellectual disability (ID). In most if it variants, the false belief task is linguistically demanding. This raises the possibility that the finding that individuals with ID do poorly on it might reflect…

Background: It is not known whether those with co-morbid fragile X syndrome (FXS) and autism represent a distinct subtype of FXS; whether the especially severe cognitive delays seen in studies of young children with co-morbid FXS and autism compared with those with only FXS continue into adolescence and young adulthood; and whether autism in those…