In a study published in the journal Neuropsychologia, a team of scientists found that some brain injuries boosted religious fundamentalism (and reduced mental flexibility) in a sample of almost 150 Vietnam War veterans.
… combat vets who suffered trauma in the ventromedial prefrontal cortex were less willing to accept new ideas and became more extreme in their religious beliefs.
The scientists studied 119 vets with penetrating traumatic brain injuries and 30 with no history of brain injury. Those who suffered injuries to the site reported higher levels of religious fundamentalism compared to those without the lesions.
The figure below shows how, compared to the healthy cortex on the far right, the brains that suffered trauma in the ventromedial prefrontal cortex (far left) and dorsolateral prefrontal cortex (second from left) had more extreme beliefs. Previously, only damage in the vmPFC was linked to more fundamentalism.
The finding indicates that “the variation in the nature of religious beliefs are governed by specific brain areas in the anterior parts of the human brain and those brain areas are among the most recently evolved areas of the human brain,” Jordan Grafman of Northwestern University, the study’s corresponding author, told PsyPost.
Damaging the area appeared to cause an increase in religious fundamentalism by reducing cognitive flexibility — or the ability to update our beliefs in light of new evidence — along with lowering the personality trait of openness.
The five authors of the study summarize their findings like this:
[P]revious research has identified the ventromedial prefrontal cortex (vmPFC) as critical to representing religious beliefs, [but] the means by which vmPFC enables religious belief is uncertain. We hypothesized that the vmPFC represents diverse religious beliefs and that a vmPFC lesion would be associated with religious fundamentalism, or the narrowing of religious beliefs. To test this prediction, we assessed religious adherence with a widely-used religious fundamentalism scale in a large sample of 119 patients with penetrating traumatic brain injury (pTBI).
If the vmPFC is crucial to modulating diverse personal religious beliefs, we predicted that pTBI patients with lesions to the vmPFC would exhibit greater fundamentalism, and that this would be modulated by cognitive flexibility and trait openness. Instead, we found that participants with dorsolateral prefrontal cortex (dlPFC) lesions have fundamentalist beliefs similar to patients with vmPFC lesions and that the effect of a dlPFC lesion on fundamentalism was significantly mediated by decreased cognitive flexibility and openness. These findings indicate that cognitive flexibility and openness are necessary for flexible and adaptive religious commitment, and that such diversity of religious thought is dependent on dlPFC functionality.
Grafman, one of the co-authors, cautions that the research was limited in scope.
“For this study, we recruited Vietnam veterans with and without brain injuries. They were all male American combat veterans. This limits the generalization to other groups of people including women, people from other countries, and people who come from cultures with different primary religious beliefs.”
We can conclude that, in some cases, extremely religious people got that way because they suffered head trauma. What the excuse is for fundamentalists without such injuries is currently beyond the powers of science to know.
(Top illustration via National Institute of Mental Health)