An exploratory study of the relationship between neurological soft signs and theory of mind deficits in schizophrenia

Indirect evidence suggests partially common pathogenetic mechanisms for Neurological Soft Signs (NSS), neurocognition, and social cognition in schizophrenia. However, the possible association between NSS and mentalizing impairments has not yet been examined. In the present study, we assessed the ability to attribute mental states to others in patients with schizophrenia and predicted that the presence of theory of mind deficits would be significantly related to NSS. Participants were 90 clinically stable patients with a DSM-IV diagnosis of schizophrenia. NSS were assessed using the Neurological Evaluation Scale (NES). Theory of mind deficits were assessed using short verbal stories designed to measure false belief understanding. The findings of the study confirmed our hypothesis. Impaired sequencing of complex motor acts was the only neurological abnormality correlated with theory of mind deficits. By contrast, sensory integration, motor coordination and the NES Others subscale had no association with patients׳ ability to pass first- or second-order false belief tasks. If confirmed by future studies, the current findings provide the first preliminary evidence for the claim that specific NSS and theory of mind deficits may reflect overlapping neural substrates.