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Can the Predictive Processing Framework Explain the Persistence of Delusional Beliefs?

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Cook, Benjamin RH 
Griffin, Juliet D 


Predictive processing (PP) provides a framework for understanding disordered cognition and experiences in terms of altered Bayesian inference. Petrovic and Sterzer (in press) re-examine its application to delusions (a project in which their own work has been central), highlighting an important paradox. If delusions emerge due to underweighting of priors relative to sensory evidence: why do they persist rather than dissolve in the face of contradictory evidence? Though Petrovic and Sterzer note that all established beliefs resist change, they view this as inadequately explaining delusional persistence. Their view is supported by Chadwick’s phenomenological description above, which illustrates that a delusion’s form crucially differs from that of an ordinary belief - implying an explanation of delusional persistence must go beyond invoking ordinary mechanisms of belief maintenance. For Petrovic and Sterzer, the solution lies in PP’s hierarchical structure. Delusional thinking emerges due to underweighted priors at lower levels, whose failure to precisely predict sensory inputs allows perceptual uncertainty to percolate up the hierarchy, where higher-level priors become overweighted to compensate for uncertainty that could not be explained away within lower-level perceptual circuits. As the authors nicely put it, this compensatory overweighting acts to “sculpt perceptual processing into conformity with delusions and foster their resistance to contradictory evidence’. For example, ambiguous visual inputs consistent with a friendly smile, interpreted in light of a patient’s higher-order belief that others are malevolent, may instead be perceived as a sinister leer – which experientially reinforces the delusional prior.



Humans, Psychotic Disorders, Delusions, Attention

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Schizophr Bull

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Oxford University Press (OUP)