Modelling delusions as temporally-evolving beliefs (Commentary on Coltheart and Davies)

ABSTRACT

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.

KEYWORDS:

• Delusions
• belief
• psychosis

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 Note that there is a good case to made that perception itself is an abductive inference and that the beliefs that emerge from perceptual experiences are abductions based on abductions. The implications of this for the Piercean pathway outlined by C&D are worth considering.

Additional information

Funding

PRC is supported by the Yale University Department of Psychiatry, the Connecticut Mental Health Center (CMHC) and Connecticut State Department of Mental Health and Addiction Services (DMHAS), an IMHRO / Janssen Rising Star Translational Research Award, NIMH R01MH12887 and NIMH R21MH120799-01. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. PCF is supported by a Wellcome Trust Investigator Award to PCF (Reference No. 206368/Z/17/Z) and the Bernard Wolfe Health Neuroscience fund.

Notes on contributors

Philip R. Corlett

Philip R. Corlett is an Associate Professor of Psychiatry and Psychology at Yale University. He received his PhD from the University of Cambridge. He is a cognitive neuroscientist with an interest in the mechanisms of psychotic symptoms like hallucinations and delusions.

Paul C. Fletcher

Paul C. Fletcher is the Bernard Wolfe Professor of Health Neuroscience at University of Cambridge. He is a Psychiatrist, interested in higher level perceptual and learning processes, and how these shape decision-making and behaviour, sometimes culminating in irrational choices.