Do extremism and an unconditional adherence to religious dogma result from a failure of a portion of the frontal lobe to fully develop or, if fully developed, to activate? Studies suggest that faithful adherence to a single reasoning strategy on tests such as the Wisconsin Card Sorting Test means that parts of the frontal lobes are inactive, have failed to fully develop, or have even been damaged. Thus, unqualified disdain for divergent beliefs,for personal interpretation, and for creative theories like Darwin’s theory of evolution, may indeed have, at least a partial, biological explanation: a reduced utilization of that section of the brain which has played such a vital role in humanity’s creative advances—the frontal lobes. By unconditionally obeying religious tenets—or any dogma—some people may be relying on the phylo-genetically older, more posterior portions of the brain that store knowledge and enable consistent or stable behaviors and, unknowingly, circumventing the portion whi

So, we can make ourselves less intelligent by adhering to a set mental pattern that disengages the ability to explore other mental avenues. Developing a "habit" way of thinking, in other words.

It's called "thought-stopping" in the context of brainwashing. Which leads us right back to many sorts of cultic and religious sorts of mind-sets.