There is a rapidly growing body of evidence for an association between schizophrenic syndromes and the absence of a clear pattern of hemispheric dominance for language. Independent work with healthy subjects suggests that one feature of right hemispheric (RH) linguistic processing is a coarse as opposed to a focused semantic activation. We provide a comprehensive review of the literature to these hitherto unrelated fields of research and present an experiment assessing functional hemispheric asymmetries for language processing in healthy volunteers, differing in the susceptibility to schizophrenia-like experiences and thoughts.
Forty right-handed men were administered a lateralized tachistoscopic lexical decision task. They also completed the Magical Ideation (MI) scale, which examines a variety of paranormal experiences and beliefs.
Although the 20 subjects with MI scores below the median displayed the expected right visual field/left hemisphere (RVF/LH) superiority in lexical decision accuracy, the 20 high scorers were equally proficient in both visual fields. Compared to the low scorers, they made significantly more correct decisions in the left visual field/right hemisphere (LVF/RH).
These results corroborate previous findings of a reduced LH language dominance for subjects scoring high on scales measuring proneness to schizophrenic behavior and thought (“schizotypy”). We propose that this dominance failure, which is commonly observed in patients with acute signs of psychosis, facilitates the emergence of paranormal and delusional ideas by way of RH associative processing characteristics, that is, coarse rather than focused semantic activation. As unfocused semantic processing is also characteristic of creative thinking, the use of the RH semantic system may constitute a selective evolutionary advantage allowing the genes predisposing to schizophrenia to proliferate despite the obvious disadvantages of this devastating disease.
© 1998 Lippincott Williams & Wilkins, Inc.