There’s a variable in the GSS, GENEEXPS, which asks if genes play a role in personality. The options are:
- It’s genes which play a major role
- It’s experience which determines personality
First, let’s admit that the premise is stupid. Personality is heritable, but environmental variation also seems to matter. In other words it is noncontroversial to assert that both genes and environment can explain variation in personality (or perhaps more precisely genetic variation can only explain around half the variation for any given trait).
I was curious how this broke down by education and intelligence. To remove demographic confounds I limited the sample to non-Hispanic whites. For intelligence I used WORDSUM, with scores 0-4 being dumb, 5-7 being average, and 8-10 being smart.
A few people have inquired of the PNAS paper On sharing genes with friends. I avoided comment in part because I’m skeptical of the findings. So much behavior genomics just hasn’t panned out over the long term, and is probably susceptible to the issues which fuel the “decline effect”. Statistical significance is a random variable too. The fundamental issue which I want to emphasize is this: many behavioral traits are highly heritable, insofar as the correlation between relatives of trait value is in direct proportion to their genetic correlation. But, just because a trait is heritable does not mean that you can affix the variation to a specific set of genes. That is because the character of genetic architecture varies, and it may be that for many behavioral traits with some biological basis the causal variants which are responsible for the range in trait values are distributed across thousands of genes, and so are of very small effect.
Carl Zimmer relayed the depth of skepticism in the scientific community yesterday, and today Dr. Daniel MacArthur reviewed the paper. Here are the top line reactions:
Liberal Überblogger Matthew Yglesias, Pulling Back The Curtain on Human Behavior:
People sometimes seem to think that you could forestall a Gattaca-esque scenario of genetic transparency through privacy laws. But it seems to me that you’d actually need to go stronger, and not only guarantee the right to not have your genetic information disclosed. To prevent the emergence of a near-universal disclosure equilibrium in a world of cheap genetic profiling over the long run, you’d need to ban voluntary disclosure. The mere fact that you don’t want a potential partner to know your DRD4 profile will tell her all she needs to know about you.
Let’s grant the power of genomics to predict behavior in this way. Let’s also neglect the real problems of banning this sort of thing in a world of commoditized sequencing or typing.* I have some news for Matt & company, there’s already a much more powerful way to behavior genetic profile someone: look at their family. Indians have long known this. So the big short-medium term problem is that getting your hands on the biodata of anyone’s family members is one-click away….
Update: A commenter points out that Yglesias may have been advocating such a position to expose the absurdity of it. I wondered that too, but wasn’t sure and thought perhaps he was serious. In any case, I think the commenter makes good points, so I retract the charge. Though the bigger point obviously still stands.
* Unless Matt has Victorian values I assume he could anticipate that it wouldn’t be too hard to get “DNA” from a prospective partner. How exactly a ban would work when there are places overseas doing sequencing I have no idea. It isn’t as if biological material is never sent through the mail.