In the present work we consider deficits in reasoning that may contribute to the maintenance of delusions by focusing on processing of disconfirmatory evidence.
According to Freeman, Garety and colleagues (Freeman, Garety, Kuipers, Fowler, & Bebbington, 2002; Garety, Kuipers, Fowler, Freeman, & Bebbington, 2001), the cognitive operations underlying delusion maintenance can be divided into two mechanisms: obtain- ing confirmatory evidence (e.g., delusion congruent attentional and memory biases) and discarding disconfirmatory evidence. These authors list a number of cognitive biases have been put forward that are particularly informative with respect to obtaining confirmatory evidence. For example, a jumping to conclusions bias may limit the amount of data gathered (e.g., Garety, Hemsley, & Wessely, 1991), an attributional bias may lead to externalization of negative events (e.g., Bentall, Kinderman, & Kaney, 1994), a theory of mind dysfunction may lead to errors in reading the intentions of other people (e.g., Frith, 1994); in addition, evidence has been presented that continual expectance of threat could lead to the misperception of social threat, the confirmation of delusional ideas, and clini- cal states of paranoia (Green & Phillips, 2004).