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Thursday, January 13, 2022

The heritability fallacy

Although Pinkerite focuses most often on the political implications of the promotion and funding of race pseudoscience, every now and then I must get technical. 

Because, although most race pseudoscience promoters are obvious oafs, there are mainstream promoters of race pseudoscience, like Steven Pinker and Jonathan Haidt, who base their support for race pseudoscience on claims that, at a causal glance, seem like they might be true. 

The kind of claims that make people you'd think would know better, like Gideon Lewi-Kraus, write an article promoting the sociobiology politics of Kathryn Paige Harden, which implied the critics of her claims are anti-science.

Harden's theories rest on the concept of heritability. Here we see Harden quibbling on Twitter with Freddie de Boer's use of the term, in a book which she generally likes.

In the same thread, professor of psychology Eric Turkheimer argues with Harden about the terminology. We can see that even people thoroughly immersed in making arguments about heritability don't agree with each other about the term.

Unfortunately Turkheimer dropped the online debate. 

Harden then went on to publish a book "The Genetic Lottery: Why DNA Matters for Social Equality" making huge claims in favor of a sociobiological approach to social policy, and, in typical sociobiology fashion waxed dramatic, claiming that those who refused to accept her claims were no better than felons.

Late last year I wrote a post about the term "heritability" and how often it is misunderstood

Not long after, a Twitter friend pointed me to this excellent paper The heritability fallacy by David S. Moore and David Shenk:

For hundreds of years, the word ‘heritable’ was used without confusion as a synonym for ‘hereditary.’ But in the early 20th century, the word was repurposed to represent something new and rather narrow...

...The term heritability was first given this new meaning in J. L. Lush’s 1937 book Animal Breeding Plans.1 In that text, Lush proposed a calculation for what he called ‘heritability’ that neatly codified the then-popular deterministic viewpoint. Because, Lush argued, an animal’s phenotype (i.e., its observable traits, such as intelligence, height, eye color, etc.) is a function of genetic instructions plus the finishing influence of the environment, we should be able to statistically separate the influence of each. Relying on mathematical guidelines from the geneticist Sewall Wright, Lush proposed that in any given group:

Vp (phenotypic variation) = Vg (genetic variation)

+ Ve (environmental variation)

Lush asserted that the Vg portion of that total can reasonably be termed ‘heritability,’ as it revealed the portion of the trait variation that could be accounted for by variation in genes. The intention was ‘to quantify the level of predictability of passage of a biologically interesting phenotype from parent to offspring’. In this way, the new technical use of ‘heritability’ accurately reflected that period’s understanding of genetic determinism. Still, it was a curious appropriation of the term, because—even by the admission of its proponents— it was meant only to represent how variation in DNA relates to variation in traits across a population, not to be a measure of the actual influence of genes on the development of any given trait. For example, in a large group of people with eyes of different colors (Figure 1), ‘Vg’ only represents the extent to which variation in the group’s DNA accounts for variation in different eye colors in that group—not whether or how DNA is responsible for the development of eye color. In that sense, it was a highly misleading new use of the term (even in the context of determinism) that was bound to cause confusion: And indeed it did...

...because the term (if not its new-fangled scientific meaning) is so familiar to the public, the casual misinterpretation of the term’s narrower meaning has been rampant in the popular press. For many decades now, we have been entertained with journalistic accounts of twin studies suggesting that ‘personality is heritable’, ‘criminals are born, not made’, and ‘cheating genes play [a] large role in female infidelity’. Twin studies have reaffirmed the strong public impression that some physical and personality traits can be passed directly from parent to child through DNA. While understandable, this impression is flatly incorrect, as brightly illustrated by three significant flaws in some scientists’ use of— and thus the public’s understanding of—the term ‘heritability.’

The article concludes:

 Heritability statistics do remain useful in some limited circumstances, including selective breeding programs in which developmental environments can be strictly controlled. But in environments that are not controlled, these statistics do not tell us much. In light of this, numerous theorists have concluded that ‘the term “heritability,” which carries a strong conviction or connotation of something “[in]heritable” in the everyday sense, is no longer suitable for use in human genetics, and its use should be discontinued.’ Reviewing the evidence, we come to the same conclusion. Continued use of the term with respect to human traits spreads the demonstrably false notion that genes have some direct and isolated influence on traits. Instead, scientists need to help the public understand that all complex traits are a consequence of developmental processes. Without such an understanding, we are at risk of underestimating the extent to which environmental manipulations can have profoundly positive effects on development. Thus, the way ‘heritability’ is used in most discussions of human phenotypes not only perpetuates false ideas; it also blinds us to steps we might otherwise take to improve the human condition.

I am beginning to suspect that psychologists who work in genetics are reluctant to drop the term heritability because the confusion masks the fact that when it comes to the claims of people like de Boer and Harden, there is no there there

And you can see why there would be a temptation to maintain the facade. Statistics-based claims about genetics give the field of psychology a quantitative aspect it normally does not have. It gives the impression that psychologists are real scientists. And if you've staked your career on that, the confusion over the term "heritable" could save you from facing an eventual reckoning, at least for the length of your professional career.