Do Born Again Christians Have Smaller Brains?

Q: Duke University conducted a study that “shows” that born again Christians have smaller brains than other protestants. I am curious to know how solid the science is. – Anonymous

Dear Anonymous,

born again christians and intelligenceThe science is solid enough; the problem here is one of interpretation. Any suggestion that Christians are less intelligent than any other group is a function of the irrepressible human tendency to believe that my group is better than your group, so neener-neener.

The study to which you’re referring is Religious Factors and Hippocampal Atrophy in Late Life (Owen et al., 2011). The media, who face the challenge of succinctly reporting complex scientific findings, have given us oversimplified and misleading headlines such as these:

There have also been more accurate headlines, such as this one in Scientific American. But naturally, various bloggers have seized the opportunity to further muddy the waters in the service of ridiculing religious folks. A commenter responding to one such blog suggested that Christians have smaller brains due to lack of use. Haw haw! Get it?

That commenter was incorrect for a number of reasons including, ironically, an obvious lack of curiosity about the true nature of the findings. (The irony, I’m certain, would be lost on him.)

Let’s Talk About Brain Size. Briefly.

The obvious implication of the oversimplified headlines is that born-again Christians are less intelligent than other groups because, as the study clearly shows, they have smaller brains.

Of course, the study does not suggest that born-again Christians have smaller brains. But as an aside, let’s take a moment to dispel the tacit suggestion that intelligence is a direct function of brain size. The two simply do not correlate neatly in humans, or even in animals. If they did, then cows, with their larger brains, would be more resourceful, agile, and socially complex than cats – and the countryside would be teeming with diabolical bovine predators rather than dimwitted future-hamburgers.

Brain size correlates with body size much more than with intelligence. Bigger people tend to have correspondingly more brain volume than smaller people, but that doesn’t mean much. Human IQ studies have found weak correlations between IQ and brain volume (Lange et al., 2010; van Leeuwen et al., 2009), and normal brain volume can vary as much as a couple hundred cubic centimeters from one person to the next (Cosgrove et al. 2007).

In fact, the relationship between brain volume and intelligence is quite complex, involving considerations such as gender differences, white matter volume, gray matter volume, processing speed, neurotransmitter efficiency, related genetic factors, and so on. To suggest that a smaller brain is a less intelligent brain is simplistic, and it has nothing to do with the study at hand. So let’s drop it. OK? OK.

Enough About Brain Size. What Did The Study Really Say?

The study, conducted by Amy Owen and her colleagues at Duke University, found abnormally high atrophy of the hippocampus among 268 people, all above the age of 58, who fell into certain religious categories. What is the hippocampus, and why should we care?

The hippocampus is a structure that lies deep within the brain and is involved with functions such as memory formation and spatial navigation. Age-related atrophy of this structure has been linked to depression, Alzheimer’s disease, and a history of chronic stress. Where stress is concerned, the hippocampus appears to be particularly susceptible to damage from cortisol, the so-called stress hormone. Hang on to that last point – it will be relevant in a moment.

The researchers tracked hippocampal volume using magnetic resonance imaging, measuring the subjects at two-year intervals. Data collection spanned eight years, with the average subject participating for 4.19 years. Here are some of the specific findings:

  • Life-changing religious experience during the course of the experiment was associated with greater hippocampal atrophy.
  • Born-again Protestant status was associated with greater atrophy than non born-again Protestant status.
  • Membership in no religious group was associated with greater hippocampal atrophy than non born-again Protestant status.

The researchers factored out other known influences on hippocampal atrophy, such as depression and life-stressors. If the study is accurate, it appears that there is a correlation between certain religious affiliations (including no affiliation) and atrophy of the hippocampus.

What does that mean? I don’t know. Neither does anyone else, but some guesses are more educated than others. The authors hypothesized that being born-again places a person in a religious minority, which is stressful. Therefore, the authors suggest, the ongoing stress of being born-again may lead to stress-related hippocampal atrophy.

It’s an interesting and plausible hypothesis, though a bit speculative for my taste. Regardless, the researchers’ conclusion is a far distant sentiment from headlines proclaiming that Christians have smaller brains.

So why have Christians been saddled with these misleading and derogatory headlines? I believe the reactions to this study underscore something fundamental in the human psyche: plain old prejudice.

Brainism: The Racism of the Future

Yale researchers this year released an intriguing study of intergroup prejudice (Mahajan et al. 2011). In a fairly clever set of experiments, the researchers found evidence that rhesus macaque monkeys are keenly aware of group affiliation, that they view those outside their own group with suspicion, and that they preemptively evaluate outsiders negatively.

To point out the obvious, humans have had countless wars, skirmishes, and disagreements based precisely on that type of thinking: if you ain’t with me, you’re against me. The intriguing point made by the Yale study is that such prejudice may be hardwired into complex species like ours.

The inclination to prejudge outsiders becomes awfully apparent when researchers discover small physical variations between people, such as – oh I don’t know – late-life hippocampal atrophy. (It also happened many decades ago when researchers began measuring head circumference.) When such findings appear, the small-minded among us seize the opportunity to attack. They are either ignorant or intentionally disregarding the fact that people in separate groups are much more similar than different. Groups may behave differently, but one group is not biologically superior to the next.

As our ability to measure the human body continues to improve, there will an increasing number of these types of studies. That means that there will an increasing number of misleading headlines about group differences, and increasingly more ignoramuses twisting the facts.

I suspect that it will get ugly at some point. At present, American society seems willing to abide a certain measure of hostility toward unfavored groups like Christians, smokers, and Republicans. There are no major upsets as long as findings like these can be aimed at acceptable punching bags. (Jeff Wise has a thoughtful posting on a related matter.) But what will happen when researchers inevitably begin to publicize trivial neurological variations between races? If history holds, bigots will rejoice at the opportunity to advance their cause.

Neurological variations like those discovered in this study are meaningless beyond their ability to add one more smidgen of knowledge about the brain in general. Statistical findings like these simply don’t apply reliably to individuals. The occasional neurological oddity vanishes in the immense constellation of traits, history, and variables that define each human life. Using piddling neurological distinctions to argue for group superiority is no different than using race or skin color for the same purpose. It is repugnant behavior.


P.S. I apologize for the uncharacteristic crabbiness. Bigotry is some of my least favorite behavior. I promise to be more cheerful next time. Hey! Here are some pictures of cute little kittens!

UPDATE: I Invited Amy Owen, the author of the study, to weigh in. She clarified a couple of points in my post, and she addressed what appear to be some of the common misconceptions about the study.

Firstly, Dr. Owen clarified my description of “abnormally high” hippocampal atrophy, which was very sloppy verbiage on my part:

“We found that there were statistically significant differences among people who fell into certain religious categories, but we could not say that some groups had an ‘abnormally high’ level of atrophy, only that some groups showed significantly greater atrophy of this brain region over time compared to other groups.”

Secondly, she clarified my statement about the researchers’ method in factoring out life-stressors:

“Your statement later in the post, ‘the researchers factored out other known influences on hippocampal atrophy, such as depression and life-stressors’ was not quite accurate – while we factored out acute stress in the last 6 months, we unfortunately did not have a measure available of the number of life stressors.”

She also wanted to emphasize that the authors viewed their stress-atrophy hypothesis as just that – a hypothesis requiring further study – and they stated so in the text of their study.

Regarding the misinterpretations that have been floating about, Dr. Owen reported that “much of the coverage has been online repostings rather than reporting by journalists, which makes it challenging to correct inaccurate descriptions of the work.” She clarified what appear to be some of the common misperceptions about the study:

“First, this study examined changes in volume of the hippocampus, a specific region of the brain, rather than the size of the whole brain. Hippocampal volume is important because atrophy in this area has been linked to clinical outcomes such as depression and Alzheimer’s Disease. We have another study that has been accepted for publication in the new journal, Religion, Brain, and Behavior, which explores the relationship of similar religious factors and changes in volume of another brain region, the orbitofrontal cortex.

“Second, everyone’s brain atrophies in late life, and different regions of the brain may atrophy at different rates. No group is immune from brain atrophy, though our study found that the rate of atrophy was associated with certain religious factors.

“Third, we did not specifically compare groups that identified as Atheists, or as religious versus non-religious. Based on participants’ responses to questions about their religious affiliation and whether they identified as born-again Christian, they were classified into groups of born-again Protestant, non born-again Protestant, Catholic, Other, or None. While those in the None category answered ‘none’ to the question about religious affiliation, they may still identify as religious or have religious beliefs, including a belief in God, just not a religious affiliation.

“Fourth, religion is a very complex, diverse, multifaceted concept, involving beliefs, world views, practices, personal experiences, communities, and cultural and historical influences. Therefore, while we investigated a small number of factors that were overtly religious (religious practices, self-reported life-changing religious experiences, religious group affiliations), we would not consider our findings to be sufficiently informative about religion overall.

“Last, and perhaps most important, we had no agenda for or against religion in our intentions for the study. Our motivations for this work were pure curiosity about the existence of any potential relationships in this sample between religious factors and mental health in late life. We consider religion or the lack thereof to be a personal choice, and would certainly not suggest anyone change religions based on our findings. We hope this study will be replicated, and that it will inspire other researchers to further explore relationships between brain structures and religious beliefs, practices, affiliations, and experiences.”

Let the record so read. Thank you Dr. Owen!

Cosgrove, K.P., Mazure, C.M., & Staley, J.K. (2007). Evolving knowledge of sex differences in brain structure, function, and chemistry. Biological Psychiatry, (62), 847-855.

Lange, N., Froimowitz, M.P., Bigler, E.D., & Lainhart, J. (2010). Associations between IQ, total and regional brain volumes, and demography in a large normative sample of healthy children and adolescents. Developmental Neuropsychology, 35(3), 296-317.

Mahajan, N., Martinez, M.A., Gutierrez, N.L., Diesendruck, G., Banaji, M.R., & Santos, L. (2011). The evolution of intergroup bias: perceptions and attitudes in rhesus macaques. Journal of Personality and Social Psychology (100)3, 387–405.

Owen, A.D., Hayward, R.D., Koenig, H.G., Steffens, D.C., & Payne, M.E. (2011). Religious factors and hippocampal atrophy in late life. Plos One, (6)3.

Van Leeuwen, M., Peper, J.S., van den Berg, S.M., Brouwer, R.M., Hulshoff Pol, H.E., Kahn, R.S., & Boomsma, D.I. (2009). A genetic analysis of brain volumes and IQ in children. Intelligence, (37), 181-191.