The Supreme Court meets the fallacy of the one-sided bet

by Andrew Gelman on April 8, 2013 · 3 comments

in Judicial,Methodology,Science

440px-Blaise_Pascal_Versailles

Doug Hartmann writes (link from Jay Livingston):

Justice Antonin Scalia’s comment in the Supreme Court hearings on the U.S. law defining marriage that “there’s considerable disagreement among sociologists as to what the consequences of raising a child in a single-sex family, whether that is harmful to the child or not.”

Hartman argues that Scalia is factually incorrect—-there is not actually “considerable disagreement among sociologists” on this issue—-and quotes a recent report from the American Sociological Association to this effect. Assuming there’s no other considerable group of sociologists (Hartman knows of only one small group) arguing otherwise, it seems that Hartman has a point. Scalia would’ve been better off omitting the phrase “among sociologists”—-then he’d have been on safe ground, because you can always find somebody to take a position on the issue. Jerry Falwell’s no longer around but there’s a lot more where he came from. Even among scientists, there’s a large enough minority with traditional moral values, that it shouldn’t be hard to find some who feel strongly that it’s harmful to raise a child in a single-sex family.

But what I really want to talk about here is not scientific consensus (which, after all, can be wrong) but a little-noticed (as far as I can tell) aspect of Scalia’s statement, which is that it’s an example of the fallacy of the one-sided bet, an argument that is artificially restricted to go in just one direction. Scalia’s saying that raising a child in a single-sex family might be “harmful to the child” or maybe not. But by framing it this way, he’s implicitly excluding a third possibility, which is that being raised in this way may be helpful to the child. What do I really think is happening? I think that the same-sex-parents environment will be helpful to some kids, harmful to others. Assuming the American Sociology Association report is correct and the research doesn’t find any aggregate effect, that would suggest that some kids are helped and some are hurt, with no clear evidence that the average effect is positive or negative. So, from the data, the effect could be positive, or it could be negative, or it could be small enough on average to consider as zero. And, just from prior reasoning, I could imagine an effect that is positive (gay parents try harder and they could be less likely to have unwanted children) or negative (maybe it’s better to have parents of both sexes and not to have to face prejudice from outsiders). I don’t know, apparently the data don’t know either. But by framing his statement the way he does, Scalia is excluding the possibility entirely.

In all this discussion I’m sidestepping the causal questions, how one might consider formulating hypothetical interventions, whether one would want to consider the “treatment” at the level of individual families or state-level policies, and the difficulties of statistical identification. These issues are important—-indeed, central to any discussion of this issue—-but here I want to focus on the one-sided argument, which is such a pervasive fallacy. I keep hoping that, by giving this error a name, I can reduce its incidence.

{ 3 comments }

Paul April 8, 2013 at 3:33 pm

Why not randomize adoptions to a treatment group of same-sex couples and a control group of hetero couples and then we can have some real social science evidence to bear on this question. Outcomes of interest would include the obvious usual suspects: grades/test scores, graduation, college going rates. But other outcomes including: teen pregnancy rates, self-identified sexual orientation, and ease with which the adopted children go through adolescence and the onset of puberty could all be identified. Me thinks folks on both sides of the debate fear the truth of what we’d find.

Blaine April 9, 2013 at 12:49 am

Of course Scalia leaves out that possibility; it’s unimaginable to him that such a thing could ever be positive for a child. He hasn’t exactly made his animus toward homosexuality a secret.

Frankly, as a gay man, I find the whole discussion soul sucking. Why does it matter what social scientists have to say about a gay couples parenting ability? It’s not like a straight couple has to subject themselves to a parental fitness exam before reproducing.

Chaz April 9, 2013 at 3:41 pm

Blaine,

I agree that gays should be able to adopt but I fear the implications of that last sentence. There’s currently no law or test preventing 14-year-old crack-addicted cult members from bearing and raising children, but I would not like to set a precedent supporting that right. I think it is appropriate to treat the welfare of the child as the primary or sole criterion for these issues, and draw a line which prohibits very unfit people from raising/controlling children. Probably best to do that on an individual basis rather than by category though.

If that means we have to have an argument over whether gays are fit or not then I can understand how insulting that feels, but let’s look a the research and have it out. In the long run, having the argument and concluding that gays are indeed fit provides the best foundation for a pro-gay social consensus and provides a good precedent for settling whatever controversies of child-rearing may erupt in the future. Getting to a consensus is very important. If we jam the issue through (only in whatever states will support it) and just say it’s rude to talk about it then conservatives will hold on to the issue and it’ll infect our politics indefinitely, a la abortion.

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