Robert Gebeloff and David Leonhardt have a recent article in The Upshot (NYT’s excellent online site for political analysis) titled “The Growing Blue-State Diaspora.” In it, they argue that increased migration from blue states to red states has been making red states bluer.

The analysis is based on actual migration data, but is based (as far as I can tell) on a mere assumption that migrants from blue states tend to be bluer than native voters in the red states they move to.

Is that assumption correct? Maybe not. For example, I was raised in Texas and lived there most of my life. But I’m one of those high-education liberals, people who are often uncomfortable living in Texas (other than in Austin). And so I left Texas and came to Washington DC, a place where I feel much more culturally and politically in sync. Could it be that this happens a lot — that liberal people are especially likely to leave red regions and settle in blue regions? And, likewise, are conservative people especially likely to leave blue regions and settle in red regions?

Something like this is behind the analyses of Bill Bishop and Robert Cushing in “The Big Sort.” The idea here is that mobile Americans have increasingly sorted themselves into like-minded communities.

Roughly, there are three possibilities:

(1) Diaspora: Migrants from blue states are more likely to be Democrats than natives of the red states they move to.

(2) Assimilation: Regardless of how they start off, migrants from blue states end up about as likely to be Republicans as those in the red states they move to.

(3) Big Sort: Migrants from blue states are actually more likely to be Republicans than others — after all, they chose to leave the blue states for redder pastures.

To check this, I turned to the U.S. General Social Survey (years 2000 to 2012). The GSS contains both the region in which the person currently lives (Region) as well as the region in which the person was raised (Reg16). I focused on two broad regions: (1) the Northeast (including New England and Middle Atlantic, roughly from Maine down through Pennsylvania and New Jersey) and (2) the South (including East South Central and West South Central, roughly from Tennessee to Texas).

These data support the Big Sort predictions. People who leave the Northeast are more likely to be Republicans than people raised in the Northeast who stay. People who leave the South are more likely to be Democrats than people raised in the South who stay. Similarly, people who migrate from other U.S. regions to the Northeast are more likely to be Democrats than natives of the Northeast. And people who migrate from other U.S. regions to the South are more likely to be Republicans than natives of the South.

In short, and somewhat weirdly, migrants from blue states make red states redder (and blue states bluer), and migrants from red states make blue states bluer (and red states redder). Just like I made Texas a little redder when I left and made DC a little bluer when I arrived. Migration patterns exaggerate rather than mute regional political differences as people seek out like-minded neighbors.

Researchers have been documenting links between genes and politics, showing in lots of cases that people’s political views have as much or more to do with their genes than with the kinds of raised-that-way factors emphasized by “socialization” theories of the past.

But what does that mean? Is there some kind of “school prayer gene” or “income redistribution gene” or “abortion rights gene” or “healthcare subsidy gene”? Of course not. So what is it about people’s genes that leads to varying political views?

In our new book, Rob Kurzban and I include a little speculation in the final chapter that maybe genes relate to things like intelligence, sociosexuality, and other relevant demographic factors, and that these genetically influenced factors affect varying political patterns in self-interested and culturally contextual ways. For an example of self-interest in action when it comes to intelligence: Some people test well and skate through higher education and thus do very well under “meritocratic” social rules. In times and places (like the contemporary U.S.) where meritocratic rules duke it out with rules based on group-based discrimination, the brainy folks tend to favor meritocratic rules, the rules that help people like them avoid being held back in social competitions. The less-brainy folks aren’t so eager to just let the smart people win — they’re much more likely to favor group-based rules that help people in their own groups and hold back people not in their own groups (based on ethnicity, religion, and whatever else is socially relevant in a given time and place).

We spend a lot of time in the book providing evidence for these kinds of self-interest claims using data from the U.S., but also confirming the overall patterns with worldwide data.

And so I was very excited to see a new article in Political Psychology, titled “Linking Genes and Political Orientations: Testing the Cognitive Ability as Mediator Hypothesis.” The authors look at political attitudes in a sample of Swedish male twins, searching for ways in which it might be true that genes affect cognitive abilities, and cognitive abilities affect political views in Sweden.

And, sure enough, they find that smart Swedes are more liberal on discrimination issues and more conservative on economic issues, and that this helps explain why genes relate to these political views.

The wheels fall off the paper when the authors speculate about why higher cognitive abilities might be associated with liberal discrimination views and conservative economic views in Sweden. They offer the wacky theory that it’s based on not-so-smart people being resistant to change. You see, immigrants bring change, and so not-so-smart people dislike immigrants. You see, Sweden has had lots of income redistribution for a while now, so pulling back from that would be change, and so not-so-smart Swedes are liberal on economic issues.

No, really, it’s a wacky theory. First, when Kurzban and I looked at worldwide data, we found, consistent with our U.S. data, that it is a very general phenomenon that less educated people like group-based discrimination and that poorer people like income redistribution. It’s safe to assume that it’s also a very general phenomenon that people with lower cognitive abilities tend to be both less educated and poorer. It’s therefore plausible to assume that people with lower cognitive abilities tend to be both conservative on discrimination issues and liberal on economic issues in lots and lots of places, not just Sweden (and, in fact, our U.S. data confirm this).

Second, looking at U.S. data, the “resistance to change” theory just fails repeatedly. For example, school prayer has been banned by the U.S. Supreme Court since the early 1960s. And yet, in our large sample, Christians with lower cognitive abilities are much more likely than Christians with higher cognitive abilities to say that they want the Supreme Court to undo (i.e., change) that long-standing anti-discriminatory policy. For another example, the U.S. has a long history of offering only very limited government help to the poor, and yet, in our large sample, people with lower cognitive abilities are more likely than people with higher cognitive abilities to want to change that long-standing reality by expanding government help for the poor. It’s just not the case that people with lower cognitive abilities routinely hold positions consistent with a dislike of policy change.

The authors offer their wacky theory, I think, for a simple reason — the obviously not-wacky theory has become practically unmentionable in some political science circles. The obviously not-wacky theory is self-interest. People who don’t win under meritocracy have self-interested reasons to favor group-based discrimination in favor of their own groups. People with lower incomes have self-interested reasons to favor income redistribution.

It makes people really uncomfortable to talk about self-interest in politics (for reasons we explore in the book). But it just becomes fluffy weirdness when (some) political scientists try to drain the real-life conflict out of political debates and turn these important policy contests into little more than spats over psychological styles — the Big Five, negativity bias, resistance to change, and so on. At some point we’re going to have to get real, as uncomfortable as that might be.