Religion is dumb, but not all religious people are dumb, but perhaps some have damaged brains. It’s not like some atheists don’t have a problem with cognitive flexibility, but theists put themselves in a different worldview with opaque walled borders that are hard to escape and penetrate.
According to Dr. Grafman and his team, since religious fundamentalism involves a strict adherence to a rigid set of beliefs, cognitive flexibility and open-mindedness present a challenge for fundamentalists. As such, they predicted that participants with lesions to either the vmPFC or the dlPFC would score low on measures of cognitive flexibility and trait openness and high on measures of religious fundamentalism.
The results showed that, as expected, damage to the vmPFC and dlPFC was associated with religious fundamentalism. Further tests revealed that this increase in religious fundamentalism was caused by a reduction in cognitive flexibility and openness resulting from the prefrontal cortex impairment.link-between-religious-fundamentalism-and-brain-damage
Finally, there is damaging proof that there is a link between fundy and mental.