[Theory of mind and schizotypy: A review]

Schizophrenia spectrum disorders are associated with incapacitating social impairments, mostly due to Theory of Mind (ToM) deficits. Theory of mind difficulties often precede the beginning of schizophrenia spectrum disorders and contribute highly to the social withdrawal of patients. They also predict bad outcome for individuals suffering from this condition. The use of samples of individuals presenting subclinical forms of schizophrenia spectrum disorders constitute an opportunity to study theory of mind capacities. Notably, the study of theory of mind deficits in schizotypy allows a better understanding of predictive markers of schizophrenia spectrum disorders. They also contribute to the identification of primary processes involved in social difficulties associated with these disorders.

We searched PubMed, Science Direct and Google Scholar databases for peer-reviewed articles studying the association between theory of mind performance and schizotypal traits up to the 1 April 2020. The following syntax was used: schizotypy AND ("theory of mind" OR "social cognition" OR "irony" OR "false belief" OR "social inference" OR "hinting task"). We also checked the references from these articles for additional papers. Only English and French written articles were considered.

Twenty-three articles were included in the review. The majority of these studies (n=20) used behavioral measures of theory of mind (i.e. percentages of correct responses on a theory of mind task). Only a few (n=3) recent studies used brain imaging to study theory of mind in psychometric schizotypy. In those 23 studies, 18 report theory of mind difficulties in individuals with high schizotypal traits. Ten out of these 19 studies report an association between positive schizotypy and theory of mind deficits/hypomentalizing. The positive dimension was the most associated with theory of mind difficulties. The negative dimension was associated with theory of mind deficits in six studies out of 19 (33 %). The association between disorganization and theory of mind deficits was weak, mostly because of a lack of studies measuring this dimension (only one study out of 13 measured this particular trait). The association between hypermentalizing and schizotypy was poorly characterized, due to high heterogeneity in how this feature was conceptualized and measured. In summary, some authors consider good performance on a theory of mind task as a sign of hypermentalizing, while other authors consider that this feature relates to the production of erroneous interpretations of mental states. We advocate in favor of the second definition, and more studies using this framework should be conducted. Interestingly, the three studies using fMRI showed no significant behavioral differences between high and low schizotypal groups on theory of mind performance, while the patterns of brain activation differed. This shows that in individuals with schizotypy, theory of mind anomalies are not always captured just by behavioral performance. Brain imagery should be included in more studies to better understand theory of mind in schizotypy. In general, high heterogeneity in ways of assessing schizotypy, and in the tasks used to evaluate theory of mind, were found. Notably, some tasks require shallower theory of mind processing than others. It is a priority to design theory of mind tasks that allow for manipulating the difficulty of the items within one task, as well as the level of help that can be given, in order to allow for a better assessment of the impact of theory of mind difficulties and the ways to compensate for them.

The studies included in this review confirm the association between psychometric schizotypy and theory of mind. But the high heterogeneity in methods used in these studies, and notably the diversity in ways of assessing schizotypal traits and theory of mind, hinder a precise description of such an association. Additional studies are required. In particular, fMRI studies using tasks allowing for a precise description of altered and preserved theory of mind processes could be of great use in characterizing theory of mind difficulties associated with schizotypy.