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March 17, 2005

The Heritability of Religiousness

Those Minnesota behavioral geneticists are at it again. Thomas Bouchard, Laura Koenig, Matt McGue and Robert Krueger have a new paper in The Journal of Personality about the heritability of religiousness that a lot of people have been talking about.

Investigating the heritability of religiousness is nothing new, of course. A host of studies have found values ranging from zero in a sample of Australian men (Truett et al. 1992) to .54 in Americans (Bouchard et al. 2004) -- the differences depending mostly on the age of the sample and the type of measure used for the phenotype. Its this first issue (changes with age) that Koenig et al. focused on.

They report:

When rating retrospectively, the MZ correlation for religiousness was .69, and the DZ correlation was .59. The difference between these correlations was not significant (Z=1.35, p>.05). When rating current religiousness, however, the MZ and DZ correlations were .62 and .42, respectively, and were significantly different (Z=2.18, p<.05). It appeared that the MZ twins maintained their similarity over time, while the DZ twins became more dissimilar. These correlations suggest low genetic and high environmental influences when the twins were young but a larger genetic influence as the twins age.


The [model fitting] estimates showed that common environment was the largest influence in the childhood data, while genetic influences were the largest in adulthood. Nonshared environmental influences, which included error variance, remained about the same over time. The genetic correlation was .59, the shared environmental correlation was .84, and the nonshared environmental correlation was .31.

Posted by God Fearing Atheist at 07:26 PM