ABSTRACT
Despite the existence of substantial literature on the social and cognitive determinants of normal beliefs and attitudes, there has until recently been a dearth of experimental data on the topic of delusional beliefs. Psychological explanations of abnormal beliefs have tended to be of two sorts. First, some authors following Maher have argued that delusions are almost always rational interpretations of anomalous experiences, and that the reasoning of deluded patients is almost always normal. Although there are grounds for believing that some delusions are driven by abnormal experiences, the evidence that this is generally the case is almost entirely negative and unconvincing. The second type of explanation of delusions focuses on the role of cognitive biases in the aetiology and maintenance of abnormal beliefs. Studies carried out by other authors have suggested that delusional beliefs are associated with abnormal hypothesis testing in some individuals. In our own research, however, we have focused on the social reasoning of patients suffering from persecutory delusions. In a series of studies we have shown that: (a) persecuted patients show an abnormal attributional style, generally attributing negative outcomes to causes external to themselves; (b) attributional biases are also evident in deluded patients’ judgements about the causes of the behaviour of other people; (c) patients with persecutory delusions show an abnormal “self-serving bias” on contingency judgement tasks; and (d) that these biases reflect selective information processing for threat-related information as shown on attention and memory tasks. Taken together, this evidence suggests that persecuted patients have much in common with depressives, and that their abnormal beliefs serve a function of preventing low self-esteem thoughts from entering consciousness. In our most recent study we have tested this hypothesis using an opaque attributional measure and other tests. As predicted, patients with persecutory delusions reported high depression and high self-esteem, but like depressives attributed negative outcomes to self on the opaque test.
