Delusions and belief formation : a cognitive neuropsychiatric approach
There is no accepted definition of belief and it is likely that the everyday use of the term does not represent a single neuropsychological entity. Nevertheless, cognitive neuropsychiatry is likely to be useful in understanding belief-related phenomena, as it does not necessarily require the focus of study to be a unitary construct. The label 'delusion' is likely to be an umbrella term for a variety of pathologies that lead a person to make an unlikely belief-claim or to have an unlikely belief attributed to them on the basis of their behaviour, in tandem with the person experiencing significant distress and / or causing social stress. Social network analyses and case studies suggested that the traditional psychopathological boundaries of delusion are influenced by socio-cultural developments and that the diagnostic criteria need revising. Despite the central role of anomalous perceptual experience in many delusion formation models, it is unclear whether it is a necessary condition. A new, valid measure of perceptual anomalies, the Cardiff Anomalous Perceptions Scale (CAPS), was developed, and a study of delusional patients suggested that pathological levels of anomalous experience are not necessary for delusion formation. A principal components analysis suggested three factors underlying anomalous experience in the general population: 'clinical psychosis', 'chemosensation' and 'temporal lobe experience'. A study using transcranial magnetic stimulation indicated that disrupting the left lateral temporal cortex in healthy participants can alter processes related to magical thinking, suggesting these areas play a causal role in delusion formation. To investigate the determinants of pragmatically pathological beliefs, as opposed to simply 'magical' ones, participants with religious beliefs (Christians and Pagans) were compared to non-religious controls and delusional patients. Pagans reported similar levels of anomalous experience to psychotic patients, but were no more distressed than the general population, suggesting distress is the more important factor in delusion formation.