I know there's a Schrödinger's cat joke here somewhere

Andrew Gelman has an excellent post up on the contradictory findings of two teams of researchers on the effect child-gender has on parents' political leanings.

Tyler Cowen reports the following claim from sociologists Dalton Conley and Emily Rauscher:

Using nationally-representative data from the [1994] General Social Survey, we [Conley and Rauscher] find that female offspring induce more conservative political identification. We hypothesize that this results from the change in reproductive fitness strategy that daughters may evince.

This surprised me, because less than a year ago, we reported here on a study by economists Andrew Oswald and Nattavudh Powdthavee with the exact opposite finding:

We [Oswald and Powdthavee] document evidence that having daughters leads people to be more sympathetic to left-wing parties. Giving birth to sons, by contrast, seems to make people more likely to vote for a right-wing party. Our data, which are primarily from Great Britain, are longitudinal. We also report corroborative results for a German panel.

Understanding the results (possibly) in terms of "family values"

This is a fun problem: we have two different studies, both by reputable researchers, with opposite results! I took a look at both papers and can't immediately see a resolution, but I will offer some speculations, followed by some scattered comments.

Andrew speculates that the differences in the findings can be explained by the fact that one study looked at the U.S. while the other looked at Britain with some additional data taken from Germany. Commenter DN elaborated further:

Seems to me that this is more likely a "law and order" effect in the US. Families with daughters are more likely to be concerned about 'protecting' their daughters against violent crime. These impacts are either mitigated in Germany and the UK (because of perceptions of the parties) or swamped by other perceived advantages of left-wing parties.

This brings up one of my least favourite practices in bad statistics reporting: generalizing conclusions about attitudes drawn from a specific culture or social group. One example that stayed with me (reported by the ever credulous NYT under the headline Bicycle Helmets Put You at Risk) was that of Ian Walker, a psychiatrist at the University of Bath. Walker, an opponent of helmet laws, put a sensor on his bike and rode with and without a helmet until he had been passed 2,500 times (see the curse of large numbers). To control for potential gender effects he sometimes donned a long wig (to get the full comic effect, check out Walker's picture below).

Walker found vehicles came on average 3.35 inches closer when he was wearing a helmet (for context, the average passing clearance was over four feet).

Putting aside for the moment questions about the methodology of the study and the sweeping conclusions Walker from it, the New York Times article works under the implicit assumption that despite major differences in traffic laws, road conditions, driver etiquette and education, vehicle type and biking culture, findings from that small stretch of English road are equally applicable to American highways.