Faith and gray matter: New study finds no relationship between brain structure and religiosity

Religion and neurology often seem at odds; an extension of the questionable chasm separating spirituality and science. Indeed, in attempting to explain religious faith, neuroscientists have often sought to highlight subtle differences in brain structure that might confirm a deficiency here or reduction there.

A new, preregistered study out of the Netherlands, published in the European Journal of Neuroscience, sought to test prominent hypotheses in the literature relating brain structure to religious experience by way of a high-powered (i.e., having a large sample size), methodologically robust study on religiosity and structural brain differences.

The need for this, according to the authors, stems from myriad methodological inconsistencies in previous research, including small sample sizes, improperly validated testing tasks, and conceptual confusion regarding the structures being measured.

Thus, while the authors readily admit that brain connectivity measures may provide a more nuanced and accurate picture of the brain-religion relation, their primary aim was to “establish the (absence of the) relation between religiosity and structural brain differences at a level of methodological and statistical rigor that we hope will set a new standard for future studies.”

In other words: to dispel notions of the most basic and simplistic relations between brain structure and religious experience, paving the way for more sophisticated approaches.

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Three theories were put to test.

First, the orbitofrontal cortex (OFC) has been implicated in religiosity for its role in error monitoring, which theorists claim must be impaired to accept religious doctrines. Previous results have been mixed, some finding the OFC to be reduced in volume, others enlarged.

Next, temporal lobe atrophy or dysfunction has been associated with hyper-religiosity, perceived communication with God, and life-changing religious experiences. The authors thus tested whether experiential aspects of religion related to reduced volume in temporal regions, including the hippocampus.

Finally, structural differences in superior and inferior parietal lobes are suspected to relate to increased likelihood of mystical experiences, on the grounds that reduced blood flow to the superior parietal lobe has been found in relation to “experiences of absolute unity” during meditation, among others.

In the study, 211 participants answered a series of questions on religiosity and religious experiences, and then underwent voxel-wise, Region of Interest (ROI) brain scans. Such scans divide the brain into three-dimensional “pixels” (voxel = volume + pixel), which can then be compared between subjects for a particular region. This allows for robust confirmatory testing of hypotheses and provides a simple fashion of quantifying differences in brain matter.

Ultimately, the authors found no relation between structural brain differences in relation to self-reported religiosity or mystical experiences, whether using ROI analysis or whole-brain analysis. To conclude, they recommend that future research forgo such attempts, and instead focus on functional and multivariate approaches.

The need to understand religious and mystical experiences runs deep, and has led to a rich and varied scientific literature. Debate continues on the best method to approach the question neurologically, and the present study should help lead to more appropriate testing methods.

The study, “The relationship between individual differences in gray matter volume and religiosity and mystical experiences: A preregistered voxel‐based morphometry study“, was authored by
Michiel van Elk and Lukas Snoek.