Objectives
Theory of Mind (ToM) is the ability to make inferences on the mental states of others. This study investigates the stateindependence and the state dependence of theory of mind (ToM) impairments in schizophrenia.
Methods
We compared the performance of healthy controls, discharged and hospitalized patients with schizophrenia on three wellknown ToM tasks, requiring mental state recognition from eyes, inferences about the mental states of others and secondorder false belief attribution. Twenty-nine patients (males and females) with schizophrenia were recruited (age range, 18-50 years) in the Psychiatric Unit of the University Hospital in Catania (Italy). Patients symptomatology was assessed with the positive and negative symptoms of schizophrenia (PANSS) scale. All subjects completed the Raven progressive matrices, and from this score a relative measure of general intellectual functioning was indirectly calculated. An Italian adaptation of Baron-Cohen’s Eyes Test was used. Participants were presented with 10 faux pas stories. 11 Two second-order belief tasks (birthday puppy and chocolate bar 12) were used.
Results
All groups of patients performed significantly worse than controls on the three ToM tests. On the Eyes Test, control subjects performed better than the outpatients (t (27) = 4.4, p < .001), inpatients with positive schizophrenia (t (31) = 6.3, p < .001) and inpatients with negative schizophrenia (t (26) = 6.2, p < .001). On the faux pas test, control subjects also performed better than outpatients (t (27) = 13.5, p < .001), in patients with positive schizophrenia (t (30) = 11.4, p < .001) and in patients with negative schizophrenia (t (26) = 13.5, p < .001). In almost all cases, the results were maintained after controlling for the mediating effect of IQ. ToM scores did not differ significantly between groups. The results revealed the presence of a specific cognitive impairment in representing and reasoning about mental states. This psychological-reasoning system is composed, to a large extent, of unconscious processes (modularity theory), and can be fractionated into two main subsystems, one dedicated, in most proposals, to reasoning about goals and perception (actional or teleological understanding) and the other to belief-desire reasoning.
Conclusions
These results support the state independence of ToM impairment in schizophrenia. However, the results provide several recommendations for future studies. One important issue is to further test the role of ToM impairment in activity of daily life in patients with schizophrenia.