Do autism spectrum disorders differ from each other and from non-spectrum disorders on emotion recognition tests?

We tested whether dimensional measures of empathic ability, theory of mind, and intelligence would differentiate autism spectrum disorders from each other and from non-spectrum disorders. Tests were administered to children with a diagnosis of Autistic Disorder (AutD; n = 20), Asperger's Disorder (AspD; n = 28), Attention Deficit/Hyperactivity Disorder (Inattentive Type) (ADHD; n = 35), Mental Retardation (Mild) (MR; n = 34), Anxiety Disorder (AnxD; n = 14), or No Psychological Disorder (NPD; n = 36). Results showed that empathic ability discriminated among groups on the autism spectrum (AutD < AspD < NPD). Because empathic ability is not independent of intelligence (AutD < AspD < NPD on intelligence; MR < ADHD < NPD on empathic ability), both dimensions are necessary to discriminate autism spectrum from non-spectrum disorders. When intelligence is covaried, empathic ability discriminated AutD, but not AspD, from other disorders (AutD < MR < ADHD < NPD = AnxD = AspD).