In most disciplines, experts oversell their ability to give useful policy advice.  In behavioral genetics, however, experts strangely undersell their ability to give useful policy advice.  Here’s a striking passage from Plomin, DeFries, McClearn, and McGuffin’s leading behavioral genetics textbook:

The idea of genetic contribution to g has produced controversy in the media, especially following the 1994 publication of The Bell Curve by Herrnstein and Murray (1994).  In fact, these authors scarcely touched on genetics and did not view genetic evidence as crucial to their arguments.  In the first half of the book, they showed, like many other studies, that g is related to educational and social outcomes.  In the second half, however, they attempted to argue that certain conservative policies follow from the findings.  But, as discussed in Chapter 18, public policy never necessarily follows from scientific findings; and on the basis of the same studies, it would be possible to present arguments that are the opposite of those of Herrnstein and Murray.

Logically speaking, the textbook is right.  The germ theory of disease doesn’t necessarily imply that we should wash our hands more.  A misanthrope could “on the basis of the same studies” argue against hand-washing, because he wants people to suffer and die.

My complaint: Plomin et al are setting up a straw man.  Policy analysts almost never argue that public policies “necessarily follow” from scientific findings.  Instead, they argue that public policies follow from scientific findings combined with some moral principles.  They usually try, moreover, to reason from relatively uncontroversial moral principles like cost-benefit analysis in order to persuade a broad audience. 

The interesting question, then, isn’t “Do the scientific findings in this book necessarily imply any policies?”  The answer to that question is “no” for all sciences and all policies.  The interesting question for a behavioral genetics textbook is rather, “Do the scientific findings in this book combined with the moral principles that policy analysts routinely use imply any policies?”

The answer to the latter question is definitely “yes.”  I’ve discussed an obvious example before: When you ignore IQ, you overstate the marginal effect of other variables.  The result: Cost-benefit analysis that ignores IQ makes educational investments look more favorable than they really are.  Herrnstein and Murray weren’t just arguing for “certain conservative policies”; they were arguing for those policies using the standard rules of the policy analysis game.

So why are behavioral geneticists so eager to downplay the practical relevance of their field?  The most plausible explanation is that these scientists already have enough trouble with political correctness.  They don’t want to amplify their public relations problem by pointing out that their science undermines a bunch of popular, feel-good policies.

Critics of behavioral genetics are prone to hyperbole, but they do have good reason to fear this science.  It really does undermine a lot of their sacred cows.  Example: If differences in talent – not differences in opportunities – explain the inter-generational income correlation, people with normal values will conclude that a lot of redistribution is unjustified.  “Giving everyone a chance to realize his potential,” isn’t the only rationale for redistribution, but it is an important one.  If people admitted that family environment has little effect on economic success in our society, there is every reason to expect a decline in support for redistributive policies.

Admittedly, the critics of behavioral genetics could reply, “We want our current level of redistribution (or more!) no matter what the science says.”  But they don’t want to say that, because it makes them sound like dogmatic ideologues.  The upshot: Behavioral genetics makes its politically-correct critics angry because the scientists are putting the politically correct in an awkward position: Deny the science, abandon some of their favorite policies, or sound like dogmatic ideologues.  It’s no wonder that they’re angry – and no wonder that they deny the science.  They’re not just making the best of a bad situation; they’re also getting a little revenge on the researchers responsible for their unpleasant predicament.