Delusional inference

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Does the formation of delusions involve abnormal reasoning? According to the
prominent ‘two-factor’ theory of delusions (e.g., Coltheart, 2007), the answer is yes. The second factor in this theory is supposed to affect a deluded individual’s ability to evaluate candidates for belief. However, most published accounts of the two-factor theory have not said much about the nature of this second factor. In an effort to remedy this shortcoming, Coltheart, Menzies and Sutton (2010) recently put forward a Bayesian account of inference in delusions. I outline some criticisms of this important account, and sketch an alternative account of delusional inference that, I argue, avoids these criticisms. Specifically, I argue that the second factor in delusion formation involves a systematic deviation from Bayesian updating, a deviation that may be characterized as a bias towards ‘explanatory adequacy’. I present a numerical model of this idea and show that my alternative account is broadly consistent with prominent prediction error models of delusion formation (e.g., Corlett, Murray et al., 2007).
Original languageEnglish
Pages (from-to)330-355
Number of pages25
JournalMind & Language
Issue number3
Early online date1 Jun 2012
Publication statusPublished - Jun 2012

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