In this paper, we appeal to the recently developed erotetic theory of reasoning in order to explain three patterns of anomalous reasoning associated with delusion: mistaking a loved-one for an impostor (as in the Capgras delusion), the well-documented tendency to ‘jump to conclusions’, and surprising improvements in a certain reasoning task involving conditionals (Mellet et. al. 2006).
According to the erotetic theory, the aim of human reasoning is to answer questions as directly as possible (for further discussion and for a formal account of the theory, see Koralus and Mascarenhas 2013). More precisely, according to the erotetic theory, reasoning proceeds by treating an initial premise or set of premises as a question and then treating subsequent information as a maximally strong answer to that question. Here is an informal illustration:
Suppose you are given a premise: there is either beer in the fridge, or there is wine and cheese in the fridge.
Informally, the erotetic theory holds that this premise will be cognitively processed by reasoners as the following question, or issue, that needs to be addressed: Am I in a beer-in-the-fridge situation or in a wine-and-cheese-in-the-fridge situation?
Now suppose the next piece of information you get is that there is cheese in the fridge. If you process that information as a maximally strong answer, resolving the issue you were trying to address, then you will conclude that you are in a wine-and-cheese-in-the-fridge situation
Of course, it would be a fallacy to draw this conclusion based on the information available. Interestingly, it is a form of reasoning that most people are naturally disposed toward (Walsh and Johnson-Laird 2004). The erotetic theory captures this pattern of tempting fallacies, along with various others documented in the experimental literature, and predicts new ones. Crucially, according to the erotetic theory, what allows human reasoners to avoid fallacies is to raise enough further questions as the reasoning process progresses. What characteristically leads us astray when we succumb to fallacies is a lack of inquisitiveness (for details see Koralus and Mascarenhas 2013).
We were curious whether, with the help of the erotetic theory, we could make sense of seemingly outlandish thought patterns associated with delusions as extreme cases of tendencies that are present in all of us. The idea was to explore a model of delusional thinking as being like ordinary thinking except lacking inquisitiveness of a crucial sort.
According to the erotetic theory, delusional thinking is conceptualised in terms of the way individuals ask questions or in terms of how they go about answering those questions. In the paper, we propose that relevant patients entertain roughly the same default questions that most people strongly associate with various external stimuli, but that they either envisage fewer alternative possible answers to these questions or raise fewer follow-up questions as they proceed to try to answer them. This chiefly has a negative effect on the quality of conclusions drawn, but we argue that it can also yield some surprising performance advantages.
In the paper, we describe how lack of inquisitiveness can make sense of various thought patterns associated with delusion. We hope this brief introduction sparks interest in renewing efforts to understand reasoning, both ordinary and delusional, more systematically than we do at present.