Meta-analyses comparing theory of mind abilities of individuals with autism, individuals with mental retardation, and normally developing individuals.

A deficit in theory of mind (ToM) abilities has been described as the core deficit in autism. The authors performed 3 meta-analyses, comparing ToM abilities of individuals with autism, individuals with mental retardation (MR), and normally developing individuals. Results indicated that individuals with autism and MR have impaired ToM abilities. The etiology associated with MR (i.e., Down syndrome, undifferentiated etiology) was found to be an important moderator variable. Chronological age (CA) and verbal mental age (VMA) of the normally developing children and CA, VMA, and performance mental age of individuals with MR, and type of matching between the groups were also found to be moderator variables. Discussion focuses on the implication of the findings and emphasizes the need to consider the specific etiology of comparison groups when studying abilities and impairments of individuals with autism and MR.