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Schizophrenia Bulletin 1999 25(3):593-600;
© 1999 by Oxford University Press and the Maryland Psychiatric Research Center (MPRC)
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© Oxford University Press

Category Learning and Perceptual Categorization in Schizophrenia

Szabolcs Kéri, M.D., György Szekeres, M.D., István Szendi, M.D., Andrea Antal, Ph.D., Zoltán Kovács, M.D., Zoltán Janka, M.D., Ph.D. and György Benedek, M.D., Ph.D.
Clinical Practitioners, Department of Psychiatry, Albert Szent-Györgyi Medical University Szeged, Hungary
Assistant Professor of Psychiatry, Department of Psychiatry, Albert Szent-Györgyi Medical University Szeged, Hungary
Clinical Practitioners, Department of Psychiatry, Albert Szent-Györgyi Medical University Szeged, Hungary
Assistant Professor of Physiology, Department of Physiology, Albert Szent-Györgyi Medical University
Associate Professor of Psychiatry, Department of Psychiatry, Albert Szent-Györgyi Medical University Szeged, Hungary
Professor of Psychiatry, Department of Psychiatry, Albert Szent-Györgyi Medical University Szeged, Hungary
Professor of Physiology, Department of Physiology, Albert Szent-Györgyi Medical University

Reprint requests should be sent to Dr. Szabolcs Kéri, Albert Szent-Györgyi Medical University, Department of Psychiatry, Semmeluris U.G., Szeged, H-6725, Hungary

The aim of this study was to evaluate category learning in schizophrenia on tests of perceptual abstraction. Participants learned to categorize simple geometrical shapes. The categories were either well-defined (discrete categories, or DCs) or ill-defined (graded categories, or GCs). In DCs, the cues defining category membership can be verbalized in an all-or-none fashion, while in GCs they cannot be defined unambiguously. Three types of learning were used successively: serial presentation of category-exemplars, verbal description, and feedback. After the serial presentation, schizophrenia patients showed a deficit for GCs (p < 0.005) but not for DCs (p=0.98). After the verbal definition of GCs, the difference between schizophrenia patients and controls diminished (p=0.09). Finally, after the feedback learning of GCs, a significant difference was observed again (p < 0.0001), suggesting that schizophrenia patients were impaired in this learning paradigm. The GC-learning impairment after the serial presentation displayed a relationship with the score of the cognitive component assessed with the Positive and Negative Syndrome Scale (r=–0.66). In conclusion, these results suggest that the perceptual stage of abstraction is impaired in schizophrenia. This impairment can be partially compensated by instructions via top-down verbal processes.

Keywords: Category learning / cognitive deficit / perceptual representation / schizophrenia


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