The aim was to find support for a [?] explanation of autism, specifically that autistic adults lack advanced theory of mind skills. Autistic subjects were compared to two groups of adults, one who were 'normal' and one who had [?] The [?]in this study was the three different groups of subjects, while the [?] was performance on an advanced test of theory of mind (eyes task). The independent variable varied naturally and was not manipulated so the method used was a [?] The eyes task consisted of magazine photographs of [?] different faces and each photo was shown for [?] seconds. Subjects were asked to choose between two mental state terms printed under each photo. Subjects in the two clinical groups were also tested using Happe's strange [?]. This was to check for [?] validity meaning that the two measures should produce similar results.The results from the eyes task show that subjects with tourette's syndrome did not differ from normal subjects but both control groups performed significantly [?] than the group with autism. Subjects with autism were [?] impaired on the Happe's strange stories task compared to the control groups. It was concluded that the core deficit involved in autism is the lack of an advanced theory of mind.