Selective impairments of theory of mind in people with schizophrenia

"Theory of mind" (ToM) means the ability to represent others' intentions, knowledge and beliefs and interpret them. Children with autism typically fail tasks aimed at assessing their understanding of false beliefs. These features of autism are strikingly similar to some negative features of schizophrenia. Mental abilities were studied in 35 schizophrenics (DSM-IV) and 17 normal controls. Subjects heard four ToM stories and simultaneously were shown cartoons depicting the action occurring in the stories. All stories involved false beliefs or deception. As for the current symptomatology, schizophrenics were divided according to Liddle's three-dimensional model (reality distortion, psychomotor poverty, disorganisation). Our results show significant differences between schizophrenics and normal controls in all ToM stories, with schizophrenic people performing worse than controls. In first-order stories (a false belief about the state of the world) significant differences were found among symptom dimensions, with the psychomotor poverty group performing worse than disorganisation subjects and reality distortion ones. As for second-order stories (a false belief about the belief of another character), the psychomotor poverty group performed worse than the other groups only in one of the four ToM stories. More research in separating ToM deficits from attention disturbances is needed.