The cognitive neuropsychiatry of delusional belief

Modelling delusions as temporally-evolving beliefs

Introduction: Delusions demand an explanation in terms of their neural, psychological, and sociological mechanisms. We must bridge these levels of explanation in order to understand and ultimately treat delusions. To this end, debates continue as to the number of contributing factors, how those factors interact, and their underlying computational mechanisms.Methods: One popular family of models suggests that two separate insults are necessary, a problem with perception and an independent problem with belief. In particular, new work proposes that the belief problem entails a bias against disconfirmatory evidence - yielding the characteristic fixity of delusions. Here, we evaluate that claim, as well as explanations of delusions more broadly.Results: We suggest that such a bias may not explain enough of the variance in belief updating in delusional participants, and, more fundamentally, it might rule out specific accounts of delusions, since, such a bias might prevent them from forming in the first place, under particular assumptions about cognitive architectures.Conclusion: We suggest conceptualising delusions as an evolving uncertainty driven negotiation between beliefs and evidence, in which initial formation is fuelled by unexpected uncertainty, but, once formed, the delusion engenders new expectations about uncertainty that tune down updating but also facilitate the elastic assimilation of contradictory evidence.

Mistrust and misinformation: A two-component, socio-epistemic model of belief in conspiracy theories

Although conspiracy theories are endorsed by about half the population and occasionally turn out to be true, they are more typically false beliefs that, by definition, have a paranoid theme. Consequently, psychological research to date has focused on determining whether there are traits that account for belief in conspiracy theories (BCT) within a deficit model. Alternatively, a two-component, socio-epistemic model of BCT is proposed that seeks to account for the ubiquity of conspiracy theories, their variance along a continuum, and the inconsistency of research findings likening them to psychopathology. Within this model, epistemic mistrust is the core component underlying conspiracist ideation that manifests as the rejection of authoritative information, focuses the specificity of conspiracy theory beliefs, and can sometimes be understood as a sociocultural response to breaches of trust, inequities of power, and existing racial prejudices. Once voices of authority are negated due to mistrust, the resulting epistemic vacuum can send individuals “down the rabbit hole” looking for answers where they are vulnerable to the biased processing of information and misinformation within an increasingly “post-truth” world. The two-component, socio-epistemic model of BCT argues for mitigation strategies that address both mistrust and misinformation processing, with interventions for individuals, institutions of authority, and society as a whole.

Bayesian accounts and black swans: Questioning the erotetic theory of delusional thinking

Parrott and Koralus argue that a particular cognitive factor--"impaired endogenous question raising"--offers a parsimonious account of three delusion-related phenomena: (1) the development of the Capgras delusion; (2) evidence that patients with schizophrenia outperform healthy control participants on a conditional reasoning task; and (3) evidence that deluded individuals "jump to conclusions". In this response, I assess these claims, and raise my own questions about the "erotetic" theory of delusional thinking.

Jumping to delusions in early psychosis

INTRODUCTION

Patients with delusions typically seek less information when making decisions than controls ("jumping-to-conclusions", JTC) and paradoxically over-adjust to counter-evidence on probabilistic reasoning tasks. Previous studies have examined JTC bias across the delusion-prone continuum, but have not considered the co-occurrence of both biases at early stages of psychosis. This was our aim.

METHOD

Twenty-three early psychosis patients and 19 healthy controls completed two versions of the probabilistic reasoning task: a "draws-to-decision" version (to assess JTC) and a "graded-estimates" version (to assess over-adjustment). Both versions have been used previously with clinically delusional people with schizophrenia. IQ, memory and executive function were also examined.

RESULTS

Patients took fewer trials to reach a decision in the draws-to-decision version and showed greater over-adjustment to counter-evidence in the graded-estimates version than controls. Across groups, those who jumped to conclusions showed greater over-adjustment. Poor executive function predicted more extreme biases in controls but not in patients. Task performances were unrelated to memory. Similar results were evident in patient and control subgroups matched on IQ, and years of formal education.

CONCLUSIONS

A jumping-to-conclusions bias and an over-adjustment bias co-occurred in the early psychosis patients. Implications are discussed concerning the role of such biases in delusion-proneness.