Abstract
The recent literature on reasoning biases in psychosis and delusions is reviewed. The state-of-the-art knowledge from systematic reviews and meta-analyses on the evidence for jumping to conclusions is briefly summarised, before a fuller discussion of the more recent empirical literature on belief flexibility as applied to delusions. The methodology and evidence in relation to studies of belief flexibility and the Bias Against Disconfirmatory Evidence (BADE) across the delusional continuum will be critically appraised, and implications drawn for improving cognitive therapy. It will be proposed that dual process models of reasoning, which Kahneman (Kahneman, 2011) popularised as ‘fast and slow thinking’, provide a useful theoretical framework for integrating further research and informing clinical practice. The emergence of therapies which specifically target fast and slow thinking in people with distressing delusions will be described.
Highlights
Cognitive models of psychosis (Freeman et al, 2002; Garety et al, 2007; Garety et al, 2001; Morrison, 2001) propose that beliefs and appraisals play a central role in determining the clinical consequence of psychotic experiences
This paper presents key research findings pertaining to reasoning biases, delusional beliefs and psychosis
Adopting a different approach involving a deductive reasoning task, Speechley et al (2010) found that individuals with delusions fail to use conflict to modulate towards ‘Stream 2’ when two streams of reasoning arrive at incompatible judgments, proposed as preliminary evidence of a Dual-Stream Modulation Failure model of delusion formation and maintenance. The findings of these clinical and non-clinical studies, despite being few in number and at an early stage of methodological development, provide some supporting evidence for the relevance of dual-process models in psychosis; in particular suggesting that slower, analytic reasoning may be protective against the development of paranoia while over-reliance on fast, experiential reasoning may be associated with unusual beliefs and paranoia across the psychosis continuum
Summary
Cognitive models of psychosis (Freeman et al, 2002; Garety et al, 2007; Garety et al, 2001; Morrison, 2001) propose that beliefs and appraisals play a central role in determining the clinical consequence of psychotic experiences. Different ways in which the construct of belief flexibility has been studied are presented, highlighting a recent rapprochement with other well-established theoretical domains; ‘dual-process’ models of reasoning which Daniel Kahneman popularised as ‘fast and slow thinking’ (Kahneman, 2011). SlowMo, a novel brief digital intervention for fears of harm from others is presented as a recent example of a treatment approach that targets reasoning biases as key maintenance factors in paranoia; an example of a wave of causal-interventionist approaches to the treatment of psychosis
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