Why do some embrace religion and others reject it outright? For a long time, scientists have been trying to answer this question by probing the neural roots of religion. Until fairly recently, many thought the answer lay in a "God-spot"—a small region of the brain that has been linked to the mystical experiences associated with faith.

Thanks in large part to the growing sophistication of brain-scanning techniques, which let neuroscientists peer into the brain’s inner workings, that concept has largely been rendered moot; there is now widespread agreement that religious behaviors are modulated by well-defined neural pathways. Indeed, several studies have indicated that the feelings of joy, doubt, and self-reflection that are evoked by intense religious experiences can be correlated with specific patterns of brain activation. Earlier this year, a group of researchers led by the National Institute on Aging’s Dimitrios Kapogiannis identified several of the cognitive mechanisms and brain circuits that seem to be engaged during the processing of religious belief.

Their findings showed that, far from being an inscrutable phenomenon, religion could in fact be experimentally addressed and that its emergence may have been driven by changes in the neural capacity for language, logical reasoning, and other evolutionarily significant processes. In a follow-up study, the same group investigated whether the expression of religious beliefs could be tied to variability in the brain's architecture. Their results, which reveal that differences in regional cortical volumes correlate with key aspects of religiosity, were reported in PLoS ONE.

In their first study, Kapogiannis and his colleagues developed a three-dimensional psychological framework that incorporated their subjects' differing perceptions of God in order to explore the neuroanatomical underpinnings of religion. Using functional magnetic resonance imaging (fMRI), they were able to associate these religious beliefs with activity in areas of the brain associated with memory retrieval, imagery, emotion, and abstract semantics. For instance, a subject who claimed to feel God’s love experienced higher levels of activity within the right middle frontal gyrus, a region associated with positive emotions.

For their new study, the authors had the same group of subjects complete a survey about their religious behaviors, their upbringing, and about particular aspects of their worldview. Whereas the intent of their first study was to illuminate the neural and cognitive activity associated with religious experiences, their objective here was to determine whether slight variations in gray matter volume correlated with different facets of their religiosity.

From the survey results they collected, they identified four components of religiosity: experiencing an intimate relationship with God and engagement in religious behavior; having a religious upbringing; doubting God’s existence; and experiencing fear of God’s anger. They then paired these findings with the results of structural MRI tests to see what relationships existed between brain volume and these components.

Confirming some of their earlier conclusions, the authors found that both religious belief and religious practice seem to be associated with networks in the brain involved with social cognitive processing. The robustness of the networks varied on an individual basis, reflecting each subject’s distinct religiosity, and seemed to fluctuate over time in response to changing stimuli. None of the networks they identified were found to be unique to religion.

The MRI results revealed that a stronger sense of intimacy with God correlated with an increase in the cortical volume of the right middle temporal gyrus (MTG). The MTG plays a key role in establishing and maintaining intimate relationships, such as the one between a mother and her child, so the authors reason that its evolution gave rise to the sense of intimacy with God that some devout individuals share.

At the other end, subjects with low MTG volumes displayed little interest in God or religion. (Schizophrenic patients, who often struggle to differentiate self from God and display aberrant religious behaviors, had the lowest volumes.)

They also found a pronounced negative correlation between the cortical volume of the left precuneus, an area involved in empathy and emotional response, and fear of God's anger. Those who felt a stronger connection with God, and thus were better able to relate God to their selves, had larger precuneus volumes and tended to be the most devout practitioners. Individuals with smaller volumes who did not form strong emotional bonds with God typically prayed out of a sense of fear, rather than out of a sense conviction or love.

Because the study only considered adults, the obvious next step would be to analyze younger age groups. Being correlational rather than causal, these findings don't really address the question of whether certain individuals were more predisposed to particular patterns of religiosity because of their brain development. The fact that no region of the brain corresponded with religiosity of upbringing rules out the contention that religious nurture alone contributes to neuroanatomical variability.

The sum total of their results suggests that religious belief may have arisen as a natural extension of evolutionary advances in social cognition and behavior. Over time, the changes in brain volume that enabled humans to show empathy towards others may have also made it possible for some to develop intimate personal relationships with a supernatural entity, thus laying the foundation for the emergence of religion.

PNAS, 2009. DOI: 10.1073/pnas.0811717106

PLoS ONE, 2009. DOI: 10.1371/journal.pone.0007180

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