Formal thought disorder (FTD) in schizophrenia (SZ) is clinically manifested primarily through language production, where linguistic studies have reported numerous anomalies including lesser use of embedded clauses. Here, we explored whether problems of language may extend to comprehension and clause embedding in particular. A sentence-picture matching task was designed with two conditions in which embedded clauses were presupposed as either true (factive) or not. Performance across these two conditions was compared in people with SZ and moderate-to-severe FTD (SZ + FTD), SZ with minimal FTD (SZ-FTD), first-degree relatives of people with SZ, and neurotypical controls. The SZ + FTD group performed significantly worse than all others in both conditions, and worse in the nonfactive than in the factive one. These results demonstrate language dysfunction in comprehension specific to FTD is a critical aspect of grammatical complexity and its associated meaning, which has been independently known to be cognitively significant as well.
*Institute of Neuroscience, Newcastle University, Newcastle upon Tyne;
†Department of Language and Cognition, University College London, London;
‡Northumberland Tyne and Wear NHS Foundation Trust, Newcastle, UK;
§ICREA (Institució Catalana de Recerca i Estudis Avançats);
∥Department of Translation and Language Sciences, Universitat Pompeu Fabra; and
¶FIDMAG Germanes Hospitalaries Research Foundation, Benito Menni Hospital, Barcelona, Spain.
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D. C. and W. H. wrote the first draft of the manuscript. D. C. processed the data for statistical analysis and ran the statistical analyses. S. W. managed and carried out recruitment and assessment. W. H. and V. Z. conceived the study. V. Z., R. V., and W. H. designed the experiment. All authors offered suggestions and edits to subsequent drafts and gave final approval for submission.
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