Theory of mind tasks in pervasive developmental disorders: interest for diagnosis

Since the initial report by Baron-Cohen et al., 1985, several studies have confirmed that, compared with normal and retarded children, autistic children exhibited lower performance in "Theory of Mind" tasks. However, it is not clear wether this failure is specific to autism or if it applies also to other patients, since other groups of Pervasive Developmental Disorders have not been extensively explored. In this study, false belief tasks (The "Sally-Ann" test and the "Box of Smarties" test) were administred to 47 children (age range 5.9 to 11.3 years), all attending a day-care psychiatric ward. The children were classified into 3 groups according to ICD-10: Autism, other Pervasive Developmental Disorders (OPDD) and other disorders (no-PDD). The results are consistent with Baron-Cohen's findings: autistic subjects fail more frequently in both false belief tasks; however, while in the "Sally-Ann" test, the difference between the autistic and OPDD group is statistically significant these two group do not differ significatively when the results of the "Box of Smarties" test are considered, because of the high number of failure in the OPDD group. Thus, the "Sally-Ann" task could be used to differentiate autism from other types of PDD, while, if these results are confirmed, the "Box of Smarties" test does not seem suitable for this purpose. Possible implications of verbal skills and/or executive functions in "Theory of Mind" tasks, are discussed.