What is new in behavioral genetics?

Here is an excellent conceptual survey article by K. Paige Harden, it goes well beyond the usual.  Hard to summarize, but here are two good bits:

An early study using a DNA-based method estimated the heritability of height to be∼80%,and it noted that this result was “consistent with results from independent twin and family studies but using an entirely separate source of information” (Visscher et al. 2006). However, although the results from DNA-based method of estimating heritability scale with the estimates from twin and family studies, the former are typically smaller (Young et al. 2019). This discrepancy between heritability as estimated from classical twin and family studies and heritability as accounted for by measured DNA was labeled the missing heritability problem (Manolio et al. 2009). Recent work has suggested that some of the missing heritability is actually “hiding” in rare variants that are not typically measured and in the heterogeneity of genetic effects across populations (Tropfet al. 2017, Wainschtein et al. 2019, Young 2019). Whether missing or hiding, the continued gap between DNA-based estimates of heritability and estimates from twin/family studies means that the latter might still be overestimating heritability due to faulty assumptions. But it is no longer reasonable, contra some predictions, to expect that advances in human genomics will reveal that the heritability of psychological phenotypes is entirely illusory.

And this one:

In contrast to what is seen for educational attainment, most studies find a minimal effect of shared environmental factors on cognitive abilities, particularly when measured in adulthood. It has been suggested,however,that this near-zero main effect of the family-level environment masks the heterogeneity of the effects of the shared environment across the SES spectrum.An early paper by Turkheimer et al. (2003) analyzed data from a sample of twins with an unusual overrepresentation of children in poverty and found substantial effects of the shared environment on cognitive ability at age 7. Subsequent research on the genotype×SES interaction effect yielded mixed results, with several studies finding null effects or even effects in the opposite direction. However, a meta-analysis of this literature (Tucker-Drob & Bates 2016) found evidence of a significant interaction effect (albeit with a smaller effect size than estimated by Turkheimer and colleagues, an example of the winner’s curse), particularly in the United States.

The importance of the shared environment for cognitive ability has also been demonstrated us-ing adoption studies. In particular, population-wide data from Sweden allowed researchers to estimate the impact of the family environment using a unique sample of male-male sibling pairs where one brother was adopted while the other brother was raised by his biological parents (Kendler et al.2015). The IQ score of the adopted brother was, on average,∼4 points higher, an increase that varied with the education level of the adopting parents.

Recommended, interesting throughout, and worth a reread as well.  I have forgotten who sent it to me, if indeed anyone did, but I thank you.



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