Schizotypal personality traits: Auditory hallucination-like experiences and atypical hemispheric lateralization

Individual differences in schizotypal personality traits (schizotypy), which might be the predisposition to schizophrenia, have commonly been explored as a means of examining the nature and structure of schizophrenia symptoms. Research on schizotypal personality in the general population may provide a particular opportunity to study the biological and cognitive markers of vulnerability to schizophrenia without the confounding effects of long-term hospitalization, medication, and severe psychotic symptoms (Raine & Lencz, 1995). A systematic review of general-population surveys indicated that the experiences associated with schizophrenia and related categories, such as paranoid delusional thinking and auditory hallucinations, are observed in an attenuated form in 5-8% of healthy people (Os et al., 2009). These attenuated expressions could be regarded as the behavioral marker of an underlying risk for schizophrenia and related disorders, just as high blood pressure indicates high susceptibility for cardiovascular disease in a dose-response fashion (Os & Kapur, 2009). Auditory hallucination (AH) refers to the perception that one's own inner speech originates outside the self. Patients with AH make external misattributions of the source of perceived speech. Recent studies have suggested that auditory hallucinations in patients with schizophrenia might occur in the right hemisphere, where they might produce irregular and unpredicted inner speech, which their auditory and sensory feedback processing system does not attribute to themselves. In the present study, general participants judged self-other attribution in speech subjectively in response to on-line auditory feedback presented through their right, left, and both ears. People with high auditory-hallucination-like experiences made external misattributions more frequently under the right-and left-ear only conditions compared with the both-ears condition. We interpreted this result as suggesting that people with a high degree of proneness to AH might have disorders in both the right and left hemispheric language-related areas: speech perception deficit in the left hemisphere and prediction violation in speech processing in the right hemisphere. A perspective that situates schizophrenia on a continuum with general personality variations implies that this disorder constitutes a potential risk for everyone and, thus, helps to promote understanding and correct misunderstandings that contribute to prejudice.