ISSN 2043-8087
Journal of Experimental Psychopathology
 Volume 3, Issue 4, 688-701, 2012
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Impaired Evidence Integration and Delusions in Schizophrenia

Authors
William J. Speechley (a), Elton T.-C. Ngan (a), Steffen Moritz (b), Todd S. Woodward (a,c)
(a) Department of Psychiatry, University of British Columbia
(b) Universitatsklinikum Hamburg-Eppendorf, Klinik fur Psychiatrie und Psychotherapie
(c) BC Mental Health and Addiction Research Institute, British Columbia

Volume 3, Issue 4, 2012, Pages 688-701
DOI: http://dx.doi.org/10.5127/jep.018411

Abstract
A bias against disconfirmatory evidence (BADE) appears to be related to delusions in schizophrenia. However, preliminary studies have either not used the most comprehensive version of the BADE task, not included a psychiatric control group, and/or have used difference score methodology instead of analyzing all available measures. In the current study a comprehensive version of the BADE task was administered to people with schizophrenia, bipolar disorder and a healthy control group. The BADE task required rating four interpretations of delusion-neutral scenarios three times (in sequence) as increasingly disambiguating information was presented. A principal component analysis (PCA) carried out on all measures determined that two independent cognitive processes appear to combine to determine all responses on the BADE task: Integration of Evidence and Conservatism, with only the former discriminating between the severely delusional schizophrenia group and all other groups. Thus, integration of evidence appears to be functioning sub-optimally in severely delusional schizophrenia patients, resulting in a bias against disconfirmatory evidence (BADE). The cognitive process theorized to be underlying this effect is hypersalience of evidence-hypothesis matches.

Table of Contents
Introduction
Methods
Participants
Procedure
Data Analysis
Results
Principal Component Analysis (PCA)
Group by Component Analysis
Discussion
Acknowledgements
References
Appendix: BADE task screen shots from a single trial.
Appendix B: Examples of BADE trials.

Correspondence to
Todd S. Woodward, Ph. D., Assistant Professor, Room A3-A116, BC Mental Health & Addictions Research Institute, Translational Research Building, 3rd Floor, 938 W. 28th Avenue, Vancouver, British Columbia, Canada, V5Z 4H4,

Keywords
decision making, principal component analysis, psychosis, reasoning, probabilistic reasoning, jumping to conclusions

Dates
Received 13 Aug 2010; Revised 2 May 2011; Accepted 30 Jun 2011; In Press 5 Feb 2012







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