Yes, that is a causal claim.

Controversial family demographer Mark Regnerus has a new post at the conservative Witherspoon Institute that links porn viewership with support for gay marriage. The tagline or abstract for the post makes the argument:

Young adult men’s support for redefining marriage may not be entirely the product of ideals about expansive freedoms, rights, liberties, and fairness. It may be, in part, a byproduct of regular exposure to diverse and graphic sex acts.

It’s a bit of a weird claim, but it’s a reasonably clear one: exposure to porn causes support for legalizing same-sex marriage. For evidence, Regnerus draws on his controversial survey to claim that:

[Of] the men who view pornographic material “every day or almost every day,” 54 percent “strongly agreed” that gay and lesbian marriage should be legal, compared with around 13 percent of those whose porn-use patterns were either monthly or less often than that. Statistical tests confirmed that porn use is a (very) significant predictor of men’s support for same-sex marriage, even after controlling for other obvious factors that might influence one’s perspective, such as political affiliation, religiosity, marital status, age, education, and sexual orientation.

Regnerus additionally cites some anecdotal evidence about the nature of online pornography, arguing that modern pornography fails to differentiate between different sorts of acts and thus.. I’m not entirely sure. Here’s the claim:

Moreover, the web’s most popular pornographic sites do little to discriminate one sex act—or category of such—from another. Gazers are treated to a veritable fire-hose dousing of sex-act diversity. … So, add to the sharing of bodies temporarily and nonexclusively a significant dose of alternative forms of sexual activity—positions, roles, genders, and numbers—and that’s basically where porn presses its consumers today: away from sex as having anything approaching a “marital meaning” or structure of the sort outlined in the article cited above.

There are rather a lot of issues one could bring up at this point – it’s not like Regnerus has a ton of credibility right now when it comes to representing (potentially) small-N subsamples from his survey right now (what percent of respondents say they watch porn daily?). But I’ll leave that sort of critique aside for the moment (but see Philip Cohen’s hilarious send-up: “Why do anti-gay people (maybe, possibly) beat their children?”). Instead, I just want to point out how after walking through this causal argument, Regnerus makes a ridiculous claim in the second to last paragraph of the post:

Of course, correlation doesn’t mean causation, and I’m not suggesting causation here.

To quote our Vice President:

Regnerus made a causal claim in the first sentences of the post. It’s backed up with a theorized (if questionable) mechanism and fun “anecdata” about pornography. And then, as soon as Regnerus claims he isn’t suggesting causation, he goes on to make the causal argument again: “But I’m also pretty confident the “causal arrow” wouldn’t run in the other direction. (Why would supporting same-sex marriage encourage you to look at porn?)”

I don’t know if Regnerus’ causal claim is right or wrong – maybe if we show a bunch of hardcore pornography to opponents of marriage equality, some of them will change their minds. It’s certainly worth trying, if we could get it past the IRB. But I do know that he just made a causal claim, and just saying the magic words “correlation is not causation” doesn’t change that. And, as much as it’s easy and fun to call it out when someone like Regnerus tries to dance this little dance, it’s a problem that’s not isolated to obviously politicized research. So, perhaps we can all remember this extreme example to help ourselves spot its subtler cousins.



  1. To clarify a bit in response to a question asked in another venue: Regnerus does hedge about the causal claim by saying that same-sex marriage views “may be” a byproduct of porn viewership. That is, he allows for uncertainty in his causal claim. But he is still very clearly making that causal connection; otherwise, there’s no point in hypothesizing mechanisms linking the two variables. So, my re-summary of his argument would be “I think there is a causal link between porn viewership and same-sex marriage attitudes, but I’m not certain.” Which is precisely what it means to suggest a causal link – the same thing Regnerus claims not to be doing.

  2. Pardon my 60s diction, but you can also look at this as a question of who’s uptight. Men who are uptight about sex are uptight about gay marriage. Men with more tolerant views of sex watch more porn, and their tolerance extends to gay marriage. Does watching porn reinforce that tolerance? It’s hard to know without longitudinal data. How about an experiment: take those anti-gay-marriage guys and have them watch a lot of porn for a while; take the pro-gay-marriage dudes and take away their porn. Then see how attitudes change. Surely the IRB will OK this one.

  3. “what percent of respondents say they watch porn daily?” About 5%, or 65 men, according to his data.

    Before you fill out the IRB forms, you should know that among this group of 65 men, only 37% strongly “strongly agreed”, not the 54% he reported. So don’t expect to find a massive effect.

  4. @Neal – Thanks so much for running the numbers!

  5. Jason Kerwin

     /  December 24, 2012

    You’re totally right, Dan, but I take issue with your describing this as “research”. This is theoretically uninformed, statistically unsound data mining, and nobody should make it out of undergrad without realizing it’s garbage. If I wrote a blog post about every single surprising correlation I found in a dataset, the internet would be filled to the brim with the nonsense I posted. Only in very rare cases can we draw the conclusion that X causes Y when X and Y are positively correlated. Reverse causality is only one of many sources of potential error in this reasoning – Jay brings up another one, and there are many more.

    To me the real question is how to properly mock this guy for continuing to do this.

  6. Thinking of porn in other cultures, the Kama Sutra came to mind. So, I bopped over to Wikipedia. The Hinduism section of the Wikipedia article Religion and homosexuality doesn’t seem very positive on gay marriage.

    Are there any other societies in time+space where pornography was as pervasive as it is now in Western society?

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