The erotetic theory of delusional thinking

Abstract

Introduction. In this paper, we argue for a novel account of one cognitive factor implicated in delusional cognition. According to the erotetic theory of delusion we present, the central cognitive factor in delusion is impaired endogenous question raising.

Method. After presenting the erotetic theory, we draw on it to model three distinct patterns of reasoning exhibited by delusional and schizophrenic patients, and contrast our explanations with Bayesian alternatives.

Results. We argue that the erotetic theory has considerable advantages over Bayesian models. Specifically, we show that it offers a superior explanation of three phenomena: the onset and persistence of the Capgras delusion; recent data indicating that schizophrenic subjects manifest superior reasoning with conditionals in certain contexts; and evidence that schizophrenic and delusional subjects have a tendency to “jump to conclusions.” Moreover, since the cognitive mechanisms we appeal to are independently motivated, we avoid having to posit distinct epistemic states that are intrinsically irrational in order to fit our model to the variety of data.

Conclusion. In contrast to Bayesian models, the erotetic theory offers a simple, unified explanation of a range of empirical data. We therefore conclude that it offers a more plausible framework for explaining delusional cognition.

Keywords:

• delusion
• erotetic theory
• reasoning
• schizophrenia
• jumping to conclusions

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Addendum

Acknowledgements

Parts of this work were presented at a graduate seminar at the University of Oxford and at the Language and Cognition Seminar at King's College London. We would like to thank the participants on both occasions for their helpful feedback. We also would like to thank Bill Fulford, Matthew Broome, and Salvador Mascarenhas for many thoughtful comments on an earlier version.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. One potential challenge is to question the extent to which an explanation of ordinary human reasoning is really ‘Bayesian’, if it always appeals to some kind of deviation from an ideal model. Although this is an important question, we shall set it aside for the remainder of this essay (see Parrott (in press) for further discussion).

2. Our discussion here will focus on the Capgras delusion. Since Ellis and Young's influential suggestion, this delusion has been at the center of much work in cognitive neuropsychology and neuropsychiatry. However, most researchers tend to think that an adequate model of the Capgras delusion would be able to be extended to other monothematic delusions (cf. Coltheart, 2007; Davies & Egan, 2013).

3. It is worth noting that this lack of responsiveness does not itself constitute the Capgras subject's anomalous experience. People are not consciously aware of their autonomic nervous system (Coltheart, 2005). Nevertheless, a disturbance in the autonomic nervous system could generate an irregular experience, perhaps an experience of something being different or wrong in some way. We need not be conscious of the internal operations of the autonomic nervous system in order for its outputs to factor in our conscious experiences. One plausible hypothesis is that disturbance in the autonomic nervous system causes aberrant prediction error signaling, which in turn alters the character of a subject's conscious experience (cf. Adams, Stephan, Brown, Frith, & Friston, 2013; Clark, 2013; Hohwy, 2013)

4. With respect to conditionals, there is some evidence that schizophrenic subjects are less susceptible to fallacious syllogistic reasoning due to belivability bias (cf. Owen et al., 2007); however other experimental work indicates there may be no significant difference between schizophrenic subjects and non-psychiatric controls (Kemp et al., 1997). Although a discussion of these results is outside the scope of the current essay, we would like to note that the erotetic theory provides a model of believability bias (Koralus & Mascarenhas, 2013).

5. This is not the only way to formally model their behaviour. The following would also work: P (yellow circle | ∼red square) < P (yellow circle ^ red square).

6. In line with several experimental paradigms, the illustration of the classical Beads Task that we give in the previous paragraph assumes that subjects are presented with sequences of at least two if not three consecutive beads of the same colour (cf. Fine et al., 2007; Garety & Freeman, 1999; Huq et al., 1988). It is worth noting that the sequences experimentally tested by van der Leer and colleagues do not begin with two consecutive colours.

7. This may have something to do with delay discounting (cf. Heerey, Robinson, McMahon, & Gold, 2007).