Thursday, 14 November 2013

Partisan heritability

I spend a week toward in my grad public choice class on correlates of political preferences.

Suppose Don Wittman is right that politics basically gives the median voter what she wants. And suppose further that Bryan Caplan is right that the best way of modeling voters is to model a normal person, and then to take away reason and responsibility. Where crazy political preferences come from then starts mattering - there's no necessary link between "what the median voter says she wants at the ballot box" and what the median voter would actually prefer if given a decisive choice.

We then hit onto some of the evidence on the heritability and policy and party preferences. Settle, Dawes and Fowler showed that identical twins are much closer in political ideology than are fraternal twins and suggested then that half the variance in strength of partisan attachment comes down to genes. Alford, Funk and Hibbing showed reasonable evidence of political orientation heritability, also using twins. Attitudes towards school prayer, property taxes, the "moral majority"*, capitalism, astrology, the draft, pacifism, unions, Republicans, socialism, foreign aid, X-rated movies, immigration and more were pretty strongly heritable. See Table 1 of their linked APSR paper. Jason Collins also maintains a great reading list on economics and evolutionary biology.

Hatemi, Dawes et al have a rather nice new paper forthcoming showing that these findings haven't been artefacts of particular datasets. But while they've found very strong evidence of heritability, they've also shown that links to particular genetic markers are fragile. Markers associated with ideology in one dataset don't show up in another - which is about what I'd expected. If you've thousands of genetic markers to choose from and you're searching in one dataset for ones that will correlate with preferences, you're bound to get some spurious correlations that will then fail to replicate in other datasets.

The ScienceNordic summary probably overstates things a bit - there's a pretty extensive prior literature on heritability of ideology, including many pieces by some of the authors of this one. But I will be adding the new piece to my graduate public choice reading list.

As I ask my grad students: now that you know that a reasonable part of your political views are basically set by your genes, how should you update the weight you attach to your own political views' correctness?

A few other obvious implications:

  • Assortative mating has gotten a lot easier with online dating websites allowing people to screen out bad ideological matches. This will lead to stronger partisan attachment, higher variance in political ideology, and greater bifurcation over time.
  • Where migration also pushes towards ideological assortment (liberals move to Boston, conservatives move to Texas), we get stronger regional heterogeneity over time. This suggests to me that more redistribution should be handled at the state rather than the federal level. 
  • Bryan Caplan's right: don't bother trying to push your kids towards your ideology. Instead, if it matters to you, choose your spouse carefully and the rest will take care of itself. 

* A right wing Christian American lobby group.


  1. All of the reading I've done on this subject makes me think that libs & cons are two different kinds of human beings who shouldn't be living in the same civilization together. If libs create a society that is congenial to the, it will feel like poison to the cons & vice versa.

    Easy solution: split America up into it's 11 natural nations

    Unpleasant solution: libs continue to dominate cons until cons can turn the tables, then process repeats.

    Ugly solution: civil war 2 (or should take the long view and call it English Civil War part 4?)

  2. South Park addressed this problem in song... Cartman concluding that having both sides is like having your cake and eating it too...'m-A-Little-Bit-Country.html

  3. Yeah I saw that episode... and I really don't buy it. America doesn't really have a functioning mainstream right-wing so there isn't any kind of "balance" going on in this country.

    Our mainstream political spectrum is actually very narrow and very hard left.

  4. I'm a bit suspicious of any table that puts Carlyle to the left of Rousseau. Carlyle supported slavery because he thought that Africans were not human but could be made human through use of a whip.

  5. I think the order is supposed to be Cromwell -> Calvin -> Carlyle -> etc. AFAIK Cromwell didn't support monarchy either.