What better way to pass a slow news Friday than with a little controversial biological determinism to explain ideological differences?

At the extreme, they found that young men who grew up with sisters but no brothers in their household are 8.3 percentage points more likely to identify with the Republican Party than boys who grow up with only brothers.

The sister effect is smaller but still statistically significant when it comes to attitudes explicitly related to gender roles. Men who had sisters were 3.8 percentage points more likely to agree that “a woman’s place is in the home” than men who did not, wrote Healy, an economist who teaches at Loyola Marymount University in Los Angeles and Mahhotra, a Stanford University political scientist…

So why are boys with sisters more inclined to identify with the GOP as young men? Researchers have found that sisters are more likely than their brothers to help wash the dishes, sweep the floor and do other traditionally gender-stereotyped tasks around the house. For example, in the data they examined, about 60% of boys but 82% of girls 10 and older with younger siblings told interviewers they were expected to help with the dishes.

This early exposure to gender stereotyping, the researchers argue, translates into more socially conservative views in later life.

Two interesting wrinkles here. One: The researchers found no similar sibling effect on girls. If boys are supposedly susceptible to having their sisters’ behavior inculcate traditional gender roles, you’d think it would cut both ways. Hmmmm. Two: There’s evidence to suggest that the sibling effect fades over time — but only in terms of party identification. Support among men with sisters for traditional gender roles remained strong even later in life. It’s their identification with the GOP that tends to soften. Presumably that’s because, as they mature, other policy considerations begin to shape their political identity. But if exposure to liberal arguments about the economy or foreign policy are making them reconsider the GOP, wouldn’t their views of gender roles also be affected by arguments about that? Maybe the difference is a simple matter of politics versus “values.” Both can change over time, but values are more intrinsic to one’s character than the questions of whether Hayek or Keynes has a better macroeconomic theory.

Another thing. Why would the world-shaping sight of a sister sweeping the floor not be offset by watching that same sister succeed in school or do well at a job? The result here seems counterintuitive to me to some degree because men with sisters get to observe women’s capabilities firsthand growing up while men without sisters don’t. It should, in theory, be easier to conclude that their place is in the home if you’re less informed about what they can do in the workplace, not more. It’s also counterintuitive to me that, if the GOP association is supposedly being driven by views on traditional gender roles, the men in this survey had a relatively weak preference for the latter (3.8 percent more likely to favor) but a strong preference for the former (8.3 percent). It should be the opposite if the researchers’ theory is true — a strong preference for traditional roles leads to a somewhat weaker preference for the GOP, since some men with sisters will gravitate to the Democrats for other reasons. Very strange.