Self-monitoring dysfunction and the positive symptoms of schizophrenia

Frith has proposed that symptoms of alien control in schizophrenia result from a defect in a metarepresentational process leading to a failure to properly monitor self-willed intentions and actions. To examine this hypothesis, a group of 40 schizophrenic patients, all meeting DSM-III-R criteria, and rated for current symptoms on the basis of a detailed clinical interview, were compared with 36 non-patient controls, using a battery of tests which included measures of self-monitoring, general cognitive function and attention. In comparison with controls, patients were impaired on two tests of self-monitoring. These differences were preserved when measures of current IQ, attention, and recognition memory were entered as covariates. Amongst patients, self-monitoring performance was related to the severity and extent of positive symptoms. These findings provide further experimental support for the proposal that positive symptoms of schizophrenia arise as a result of deficiencies in self-monitoring.