Investigating the Specificity of Dual-Processing Deficits to Delusions

Authors

  • Patapia Tzotzoli This study was conducted as part of the requirements of the MPhil in Biological Sciences, Department of Experimental Psychology, University of Cambridge, United Kingdom, completed by Patapia Tzotzoli https://orcid.org/0000-0001-7110-5502
  • Rhianna Goozee Independent Scholar, London, United Kingdom https://orcid.org/0000-0003-0105-4302
  • Alexios Arvanitis Department of Psychology, University of Crete, Rethymnon, Greece https://orcid.org/0000-0002-3379-0286
  • Marietta Papadatou-Pastou National and Kapodistrian University of Athens, Athens, Greece; Department of Pedagogy and Primary Education, Biomedical Research Foundation of the Academy of Athens, Athens, Greece ; Department of Social Sciences, School of Humanities and Social Sciences, University of Nicosia, Nicosia, Cyprus https://orcid.org/0000-0002-2834-4003

DOI:

https://doi.org/10.13129/2282-1619/mjcp-5394

Keywords:

Delusions, Heuristics, Reasoning, Schizophrenia

Abstract

Objective: Delusions, a defining characteristic of schizophrenia, are considered a consequence of aberrant reasoning. However, it is unclear whether aberrant reasoning reflects a more general deficit in schizophrenia. This study aimed to investigate differences in intuitive reasoning (System 1) and analytical reasoning (System 2) between individuals with schizophrenia, with and without delusions, and controls. We hypothesized that individuals with schizophrenia would exhibit impaired performance on System 2 tasks compared with controls, deluded patients would show greater impairments on System 1 tasks, and deluded patients would differ from non-deluded patients and controls in response modifications across task trials.

Method: Participants included 14 patients with schizophrenia with delusions, 12 patients without delusions, and 22 controls. Cognitive reasoning was assessed using the verbal Odd One Out subtest, a Kahneman Reasoning Test designed to evaluate heuristic-based reasoning, and a non-Kahneman Reasoning Test. The study also examined participants’ abilities to modify responses across trials following feedback.

Results: Findings supported only the first hypothesis (Odd One Out Test, p = .006; non-Kahneman Reasoning Test, p = .03), confirming a deficit in analytical reasoning. However, performance on the Kahneman Reasoning Test was comparable across groups, with no detectable group differences in heuristic reasoning. Deluded patients did not differ from non-deluded patients or controls in heuristic or analytical reasoning.

Conclusions: Findings suggest that schizophrenia is associated with selective deficits in analytical reasoning while no impairment in heuristic reasoning was detected. These findings challenge prior assumptions about delusion-related cognitive dysfunction and highlight the need for future research to explore the mechanisms underlying apparently preserved heuristic reasoning in schizophrenia.

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15-08-2026

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Vol. 14 No. 2 (2026)

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