A new study examining delusions—strongly held beliefs despite superior evidence to the contrary— has been conducted in healthy adults. The paper was published in the Journal of Neuroscience by a group of neuroscientists in Berlin, Germany, led by Katharina Schmack. They used fMRI techniques on volunteers to measure connectivity within the brain, in conjunction with behavioral questionnaires and perceptual tests to determine the strength of learned visual inferences as a function of delusional ideation. The basic idea was to test whether people with delusional tendencies are flexible in their perception—that they harbor weak predictions about how the world looks—and are therefore perceptually unstable. They were.
In each subject, the scientists also imaged the brain to determine if delusional people have overly strong functional connectivity between their frontal lobes and their visual cortex. And it was true.
So lack of clarity about how the world works is implicated in delusions, along with overly strong—stubborn—beliefs that sculpt perceptual data into conformity. Notice that this study examined individual differences within the healthy population: these are your friends and family members who feel unreasonably persecuted or overly confident in their connection with a higher power.