Symptomatology and social inference: A theory of mind study of schizophrenia and psychotic affective disorder

Introduction. There is evidence that certain patients with schizophrenia have deficits in theory of mind (ToM) capabilities. It is, however, unclear whether these are symptom or diagnosis-specific. Methods. A ToM hinting task was given to 15 patients with a DSM-IV diagnosis of schizophrenia, 15 patients with affective disorder and 15 healthy controls. Severity of the current psychopathology was measured using the Krawiecka standardised scale of psychotic symptoms (Krawiecka, Goldberg, & Vaughan, 1977); IQ was estimated via the Ammons and Ammons Quick Test (Ammons & Ammons, 1962). Results. The group with schizophrenia performed significantly worse than the affective and control groups. Poor performance on the hinting task was found to be significantly related to the presence of positive symptoms (instead of negative ones) and specifically related to delusions and hallucinations. These findings remained when covariance for potentially confounding variables was applied. Conclusions. Individuals with high levels of delusions and hallucinations performed significantly worse on this ToM task, regardless of diagnosis, implying ToM impairment is not exclusive to schizophrenia but is evident in other forms of psychosis. Between-group analyses showed the schizophrenia group had a significicantly poorer performance on this task than the others. © 2005 Psychology Press Ltd.