The paradox of delusions: Are deluded individuals resistant to evidence?

Nicholas Furl, Max Coltheart, Ryan McKay

Research output: Chapter in Book/Report/Conference proceedingChapter


Delusions are pathological beliefs, often with bizarre content. They feature in neurological disorders and in psychoses associated with psychiatric disorders (e.g., schizophrenia). In this chapter we review two apparently opposing ways that the research literature characterizes delusions. While delusions are often defined as beliefs that are rigid and unaffected by evidence, they are also frequently conceptualized as beliefs that are unduly swayed by minimal, insufficient evidence. We review empirical studies and theory from psychology, neuroscience and computational psychiatry which embody this contrast. Prevailing perspectives, we show, frame belief formation as a process of integrating new evidence into existing beliefs. This view tends to sculpt hypotheses about delusions (and other psychotic symptoms such as hallucinations) into two types. First, relevant evidence fails to affect prior beliefs, which are too entrenched. Second, evidence overly dominates prior beliefs, which have too weak an influence. This paradox, we argue, calls for a profound rethinking of these perplexing and distressing symptoms.
Original languageEnglish
Title of host publicationBelief, Imagination, and Delusion
EditorsEma Sullivan-Bissett
Place of PublicationOxford
PublisherOxford Univerity Press; Oxford
ISBN (Print)978-0-19-887222-1
Publication statusPublished - 18 Jan 2024

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