Delusional belief

Some forms of delusional belief are well explained by a neuropsychological theory that posits the necessity of two distinct neuropsychological deficits in such conditions: one that is an impairment of perceptual or emotional processing, responsible for the content of the belief, and a second that is an impairment of a right hemisphere system for belief evaluation and is responsible for the failure to reject the belief despite the evidence against it. This theory is described and its application to various delusions is demonstrated. Some forms of delusion, however, do not seem plausibly describable as neuropsychological in origin. Whether the two-deficit theory might be expanded to deal with these delusions is discussed.