Field of Science

Religious fundamentalism is in the genes

The question of nature versus nurture crops up a lot in discussions of religion. Here's a study that came out at the end of last year that took a look at the problem.

It's a fairly standard twin study. They took a sample of around 600 identical and non-identical twins from the National Survey of Midlife Development in the United States (MIDUS), and looked at a number of religious characteristics.

Basically, their analysis allows them to tease out the variations that are shared by identical twins but not by non-identical ones (genetic factors), by non-identical twins (family factors or shared environment), and that differed even among non-identical twins. This last factor was put down to the effects of external environment (i.e. things that happen in you life that aren't shared by your twin).

I've put the results in the graph. First off, look at childhood religiosity. The biggest factor is your family, and not your genetics. It's not until adulthood that the effects of genetics really start to shine through. No surprises there!

The 'salience', or importance of religion in your life is about one-quarter defined by genetics, as is your spirituality. The most important factor here, however, is the external environment. You get similar results for religious attendance.

When you get to more personal beliefs, the patterns start to shift. There are three factors that are about 40% driven by genetics, with your family upbringing having hardly any effect. These factors are: how often you turn to religion for guidance, whether or not you take the bible literally, and whether people should stick to one faith, or experiment with others (exclusivist beliefs).

As discussed earlier, Jonathan Haidt (psychologist at the University of Virginia) has investigated conservative psychology and found it to be linked to the need for order and the fear of uncertainty. To me, these three religious attitudes are similar to conservative attitudes. I wouldn't be surprised if these psychological factors trigger both conservatism and religiosity.

But the big finding in this study is the born-again religious. These are the people who answered 'yes' to the question: “Have you been ‘born-again,’ that is, had a turning point in your life when you committed yourself to Jesus Christ?” A whopping 65% of this kind of religiosity is genetically driven!

This is particularly amusing given that most of what passes for debate on this topic seems to be between atheists and fundamentalists. If the debate often seems futile and sterile then these data might suggest why. Religious fundamentalists are born, not bred. It's not a matter of evidence or rational argument. They just can't help it!
MATT BRADSHAW, CHRISTOPHER G ELLISON (2008). Do Genetic Factors Influence Religious Life? Findings from a Behavior Genetic Analysis of Twin Siblings Journal for the Scientific Study of Religion, 47 (4), 529-544 DOI: 10.1111/j.1468-5906.2008.00425.x


  1. I'm interested to know how these researchers define and measure a person's "spirituality".


  2. I'd love to see quite a few of their operational definitions, and how they determined what was genetically driven... I would suspect it to be rather difficult to isolate family impact from genetic impacts in identical twins. Are they assuming that things that happened to both later in life are genetic?

  3. Here's the operational definitions:

    Childhood religiosity is tapped with the following retrospective question (coded 1 = not at all to 4 = very much): “How important was religion in your home when you were growing up?” Religious salience is a six-item summed index (Cronbach’s alpha = 0.88; each item is coded 1 = not at all to 4 = very). Specific items include: (a) “How religious are you?” (b) “How important is religion in your life?” (c) “How important is it for you—or would it be if you had children
    now—to send your children for religious or spiritual services for instruction?” (d) “How closely do you identify with being a member of your religion?” (e) “How much do you prefer to be with other people who are the same religion as you?” and (f) “How important do you think it is for people of your religion to marry people who are the same religion?”

    Spirituality is gauged with two items (alpha = 0.91; each item is coded 1 = not at all to 4 = very): (a) “How spiritual are you?” and (b) “How important is spirituality in your life?” Daily guidance and coping is tapped
    with two questions (alpha = 0.85; each is coded 1 = never to 4 = often): (a) “When you have decisions to make in your daily life, how often do you ask yourself what your religious or spiritual beliefs suggest you should do?” and (b) “How often do you seek comfort through religious or spiritual means such as praying, meditating, attending a religious or spiritual service, or talking to a religious or spiritual advisor?”

    Conservative ideologies are gauged with two single-item measures. Biblical literalism, a commonly employed measure of religious conservatism, is tapped with the following question: “How much do you agree or disagree with the following statement (coded 1 = strongly disagree to 5 = strongly agree): “The Bible is the actual Word of God and is to be taken literally, word for word?” Exclusivist beliefs are measured with the following question (coded 1 = yes and 0 = no): “Do you believe that one should: stick to one faith?” For this variable, respondents who answered “yes” are compared with those who believed that individuals should “explore different teachings,” do “neither” of these things, or “don’t know” the answer to this question.

    For the analysis, they used a standard 'twin analysis' package, but only give a few details:

    Using the publicly available SEM package Mx (Neale et al. 2003), the following three structural models are fit to the data (using maximum likelihood analysis of variance-covariance matrices) for each of the eight religion measures (separately): a full model that decomposes observed individual-level variation into latent genetic, shared environmental, and nonshared environmental components; a reduced model that drops the shared environmental component; and a reduced model that drops the genetic component.

  4. Hmm, very interesting. Clearly, the Calvinists were right, and god predetermines who gets to heaven and who doesn't!

    (I realize this is my first post here, so I feel the need to say that yes, I am joking)

  5. Unlike the other categories, being "born again" seems to be an experience that one either "gets" or doesn't. Thus I'm not so surprised to see a strong hereditary component here.

    It would be interesting to also test measures of suggestability in this sort of study.

    It would also be interesting to test subjects in other cultures. Here in Thailand, there's not much of a notion of "born again". Nor do you run into many people who are hugely dogmatic about, say, the meaning of the Tripitaka. There does, however, seem to be a big split between folks who are "good" meditators and those who are not.

  6. My entrance into fundamentalism came when I was a mid-teen, no significant prior religious exposure in the immediate family. But I noticed in my own life, and the lives of others who "got saved" as teens or young adults, we all or mostly came from families with strong alcohol and/or drug addicted parents. This is anecdotal, not scientific, of course, but I'd love to see some science on the relationship between addiction-based rigidity in the home and religion-based rigidity in the home, and how it affects one's later propensity toward rigid religiosity as a response to avoiding the addiction of one's parents, while perpetuating the rigid personality traits. I don't know if that even makes sense to someone else, but it makes sense to me.

  7. Ngong, one of the things that occurred to me about this study is what the effect would be of genes that encouraged you to follow what others in your environment were doing. I guess they would not be identified as genetic effects.

    You are right also, that this needs to be looked at in different cultures, to see if the findings are robust.

  8. I expect that, since researchers are trying to measure spirituality, that they'd also be quite interested in measuring stupidity. They seem to be on the same curve.

  9. I am coming to this late, but I see some problems with this study.

    First, most religions do not have any sort of "born again" doctrine. It is strictly a Protestant phenomenon, though I suppose some Catholics may indulge in it and then return to their churches. So I would imagine that the "born again" result is dependent on factors not measured in the study, like one's denominational affiliation and background. I share the interest of other posters in what the results would look like outside the US - ours is a religion-saturated nation.

    Second, for literalism, exclusivity, conservatism, service attendance, and "born again" beliefs, there seems to be a Great Divide between genetics and external environment, with little influence from childhood, but not for religiosity as measured. This may be partly because the study measured religiosity with questions using the words "religion" and "spirituality". No doubt you are aware of a PR ploy among certain fundamentalists to the effect that theirs is not a religion, but a "personal relationship" with their imaginary friend. Fundamentalists under the sway of such a doctrine might mark "religion" as unimportant, and unspecified "spirituality" might, to them, smack of New Age paganism, to be strongly avoided. This may have biased the results, and may account for the mushy measures of religiosity.

  10. Unfortunately almost all data come from the USA. I'd imagine the results would be quite different in other countries because no doubt some of the link is down to genetic predisposition to 'conservatism' versus 'openess to experience'. In Europe, the religious are fewer but those that are religious are more closed-minded.

    I don't know what kind of personality is attracted to 'born again' style religion, and it would be interesting to find out where such personalities end up in non-protestant countries.

    I didn't know that about fundamentalists! But I'd agree, it's more evidence that generalised measures of 'religiosity' are pretty soft since they are so open to differing interpretations.


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