 Relevant to the question whether delusions are rational, the empirical literature suggests that our reasoning performance when we have delusions reflects data-gathering and attribution biases. For instance, it has been argued that people with delusions ‘jump to conclusions’; need less evidence to be convinced that a hypothesis is true (Garety 1991; Huq et al. 1988; Garety and Freeman 1999); and are more hasty in their decisions (Moritz and Woodward 2005; Fine et al. 2007). Other biases have also been noted: people with delusions of persecution tend to attribute the responsibility of negative events to other people (e.g., McKay et al. 2005b) whereas in the Cotard delusion there seems to be a tendency to attribute the responsibility of negative events to oneself (Young and Leafhead 1996; Gerrans 2000; McKay and Cipolotti 2007). People with delusions seem to be worse than controls at inhibiting the evidence of their senses when it conflicts with other things they know (Langdon et al. 2008b) and have an accentuated need for closure which comprises a desire for clarity and structure (see Kruglanski 1989, p. 14). These data are not by themselves sufficient to support the view that delusions are irrational, but show that we can  deviate from statistically normal reasoning performance when we have delusions.