Seriation, conservation, and theory of mind abilities in individuals with autism, individuals with mental retardation, and normally developing children.

Seriation, conservation, and theory of mind abilities were examined in individuals with autism (N = 16), mental retardation (N = 16), and in normally developing children (N = 16). Seriation tasks included seriation of tubes, blocks, and flat squares. Conservation tasks included conservation of area, number, substance, quantity, and weight. Theory of mind tasks involved predicting false belief and understanding value and fact beliefs. Participants with autism performed better than participants with mental retardation on seriation, while no differences emerged between these groups on conservation and false belief. Individuals with autism performed less well than individuals with mental retardation on the value and fact belief tasks; however, when verbal ability was held as a covariant, the difference was no longer significant. Normally developing children performed better than the other two groups on all tasks. These results suggest that autism does not involve a specific impairment in theory of mind and that theory of mind deficits are not unique to autism.