Michael:

Some time ago you mentioned in a posting that you (at least half jokingly) attributed the persistence of religion in modern secular society to the fact that people must have a gene for religious belief. Not long after, I was rather surprised to stumble across something at least supportive of this notion (although probably not as a result of anything so neat as the operation of a single gene) .

In Matt Ridley's book, "Nature via Nurture: Genes, Experience and What Makes Us Human" he discusses some of the interesting differences in correlations found between identical twins reared apart (that is, individuals who share all their genes and little or none of their environment) and in fraternal twins reared apart (that is, individuals who share roughly half their genes and little or none of their environment) on the topic of religion:

In a recent study [psychologist Thomas] Bouchard measured how [religiously] fundamentalist individuals are by giving them questionnaires about their beliefs. The correlation between the resulting scores for identical twins reared apart is 62 percent; for fraternal twins reared apart it is just 2 percent. Bourchard repeats the exercise with a different questionnaire designed to elicit a broader measure of religiosity and still gets a strong result: 58 percent [for identical twins reared apart] vs 27 percent [for fraternal twins reared apart].

And that ain't all. Similar effects seem to crop up in political opinions, or at least right-wing political opinions:

[Bouchard] repeats the exercise with a different questionnaire designed to discover what he calls "right-wing attitudes." Again there is a high correlation in identical twins reared apart (69 percent) and no correlation at all in fraternal twins reared apart. He gives the twins a different questionnaire that simply lists single phrases and asks for approval or disapproval: immigrants, death penalty, X-rated movies, etc. Those who reply no to immigrants, yes to the death penalty, and so on are judged more "right-wing." The identical [twins reared] apart correlation is 62 percent, the fraternal [twins reared] apart correlation is only 21 percent. Similar huge differences [in the similarity between the political opinions of identical twins and fraternal twins reared apart] emerge from similar large studies in Australia.

All this, of course depends on the (apparently reasonable) assumption, hopefully accounted for by Mr. Bouchard and his Australian counterparts, that adoptive homes represent a spectrum of religious and political opinion; if the adoptive parents were all right- or left-wing, and all highly religious or utterly irreligious, these results would be about how genes control the receptiveness of children to their parent's religious and political views. But this conclusion is unlikely if the studies embraced any very large group of adoptees and adoptee families.)

Gee, do you suppose there are tests designed to measure or categorize aesthetic tastes (Elvis vs. the Beatles, abstract painting vs. representational, ballet vs. modern dance) that we could get introduced into these twin studies? I wonder how heritable such aesthetic preferences would turn out to be?

Cheers,

Friedrich

Fried - It's a twin study so I have to ask - how many twins, what method was used to determine identical and fraternal, and what about twins who were legally "raised apart" although they grew up in the same community and knew the same family group - are such twins part of the survey? Do the twins who were raised apart know each other? If so, at what age did they make contact? Does Bouchard say?

The big question is what method was used to determine identical or fraternal.

Posted by: j.c. on June 20, 2003 4:23 PM

I tend to think my conservatism is more temperamental than ideological, a function more of who I am than what I believe. It makes sense that there'd be some genetic predisposition for all that.

But I have to wonder, is there also a genetic predisposition for left-wing beliefs? And if parents discovered that their unborn fetus was very likely to grow up a Che-worshipping Marxist or a Reagan-loving fundie, would they choose to abort?

Posted by: Tim Hulsey on June 20, 2003 5:02 PM

J. C.--

I haven't read the original studies, but if you'd like to check them out you'll find them, according to Mr. Ridley's notes, at

Bouchard, T.J., McGue, M., Lykken, D., and Tellegen, A. 1999. Intrinsic and extrinsic religiousness: Genetics and environmental influences and personality correlates. Twin Research 2:88-98.

The Australian study can be found at

Kirk, K.M., Eaves, L.J., and Martin, N. 1999. Self-transcendence as a measure of spirituality in a sample of older Australian twins. Twin Research 2:81-7

Unless Ridley is a dupe (possible, but he is the former science editor for The Economist) Bouchard seems to be a pretty careful scientist:

[In 1980] Susan Farber published a book disparaging all studies of identical twins reared apart as unreliable. The studies exaggerated similarities, ignored differences, and skated over the fact that many twins had spent many months together as infants before their adoption or had been reunited many months before being seen by scientists. Some of [previous twin] studies, such as Cyril Burt's, were perhaps even fabricated altogether [actually, almost certainly not true, as his data matches quite careful follow up studies very closely.] Farber's book was seen as the last word on the matter, but Bouchard merely saw it as a challenge to do a flawless study. He was determined not to leave himself open to such accusations, and he carefully recorded everything about his pairs of twins...By the time he published, his data were all but impregnable to Farber's criticisms. Not that this impressed the establishment.

Not to put too fine a point on it, but the attacks on twin studies have a certain, how shall we say, political component to them. The investment of certain parties in the notion that human nature is strictly a social construction seems too profound to give up in the face of mere evidence.

Posted by: Friedrich von Blowhard on June 20, 2003 7:01 PM

I'm betting that there's a big genetic/biochemical component to aesthetic preferences, as there seems to be to religious and political preferences. Makes sense -- why wouldn't there be, really? I remember reading a study that broke people down into two groups, one that preferred heating-up, one that preferred cooling-down -- this was just the way they preferred to meet new situations. And it seemed pretty clear that the heating-up group tended to prefer a Romantic p-o-v and leftish politics, and the cooling-down group tended to prefer a Classical p-o-v and conservative politics. Maybe you prefer what you prefer because that's what the (bio-genetic) creature that you are prefers, and maybe there isn't a lot more to it than that. Bye-bye, art-criticism arguments...

Posted by: Michael Blowhard on June 21, 2003 1:15 AM

Funny, I have just gotten to that part of the book and was noting the same passage with interest. My thoughts: If there is a genetic component to religiosity and conservatism, then logically there has to be a genetic component to skepticism and liberalism. Take that questionaire for right-wing thoughts: Unless I am missing something with regards to basic logic, it is simultaneously a questionaire for left-wing thoughts, as it is a simple (2) multiple choice test. If there is a 62% correlation in the answers for genetic twins reared apart, it would seem to me that this correlation would hold regardless of how liberal or conservative your answers are.

Which raises the question, why are we zooming in on genetic causes for conservatism, but not liberalism? As a liberal atheist, it doesn't make me feel any better that Bush can't help himself.

Posted by: Stefan on June 23, 2003 9:41 AM

Thanks. A lot of this seems to come from Minnesota twin, who are (I think entirely) identified by DNA tests and there have been serious makes some effort to identify truly separated at birth twins from twins who were merely shuffled around in foster care. Looks like most of the surveys were done by mail.

Don’t think it’s political. There’s an ugly history of twin studies in which the twins were identified as identical or not without testing, and the “surveys” where done by grad students quizzing the twins, twins they knew to be identical or not, in person – sometimes with both twins in the room… sometimes with both twins in the same room for the fifth or six time these “raised apart” identical twins had been interviewed for a study.

It’s not like we’ve gotten over being superstitious about twins.

Posted by: j.c. on June 23, 2003 12:47 PM






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