Recently I read the Harvard Journal of Law & Public Policy article by Sherif Girgis, Robert P. George, and Ryan T. Anderson, titled “What Is Marriage?” (The article, I am told, has been extensively revised and expanded, and has just been released as a book.) Their explanation of marriage’s distinctiveness as a one man-one woman union includes the following claim:

Marriage has its characteristic structure largely because of its orientation to procreation; it involves developing and sharing one’s body and whole self in the way best suited for honorable parenthood—among other things, permanently and exclusively.

Given that I study the sexual and relationship lives of emerging adults, I couldn’t help but note the contrast between this description of marital sexuality and how sex is portrayed in modern pornography. Indeed, the latter redirects sex—by graphic depiction of it—away from any sense of it as a baby-making activity. Porn also undermines the concept that in the act of sexual intercourse, we share our “body and whole self … permanently and exclusively.” On the contrary, it reinforces the idea that people can share their bodies but not their inmost selves, and that they can do so temporarily and (definitely) not exclusively without harm.

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. (These are not your grandfather’s Playboy.) 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.

With this in mind I began to wonder about a possible link between porn and sentiment toward same-sex marriage, given the latter’s blending of something conventional—marriage—with something less conventional—homosexuality. Now, before you jump off my train of thought, let me assure you of where it’s not headed. I’m not talking about any correlation between same-sex relationships and porn use (although that would be an answerable research question).

Nor am I talking about women’s support for same-sex marriage. Women typically aren’t as into porn as men are, and yet women in general tend to support same-sex marriage more readily than do men. A recent Gallup poll noted that 56 percent of women favor it, while only 42 percent of men do. No, this theory is not about women. It’s about men—those Americans with the more significant penchant for porn and the more misgivings, on average, about same-sex marriage. Does heightened porn use matter for fashioning attitudes about marriage?

If Girgis, George, and Anderson are onto something by arguing that marriage has a characteristic structure that is—if I’ve hypothesized correctly—undermined by porn, then men with more frequent-use patterns should be less supportive of “traditional” marriage and more supportive of redefinition efforts. While I realize that eight of the top ten states in terms of online porn consumption voted Republican in the 2008 presidential election, I’m analyzing individuals’ survey responses, not state-level data, which prevents me from falling into the trap of the ecological fallacy, or deducing things about individuals from the groups of which they are a part.

Data from the New Family Structures Study reveal that when young adult Americans (ages 23-39) are asked about their level of agreement with the statement “It should be legal for gays and lesbians to marry in America,” the gender difference emerges, just as expected: 42 percent of men agreed or strongly agreed, compared with 47 percent of women of the same age. More men than women disagreed or strongly disagreed (37 versus 30 percent), while comparable levels (21-23 percent) said they were “unsure.”

But 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.

The same pattern emerges for the statement, “Gay and lesbian couples do just as good a job raising children as heterosexual couples.” Only 26 percent of the lightest porn users concurred, compared to 63 percent of the heaviest consumers. It’s a linear association for men: the more porn they consume, the more they affirm this statement. More rigorous statistical tests confirmed that this association too is a very robust one.

Theoretically, the same pattern should hold when considering support for marriage in general. And it does, though not quite as distinctively. The less time spent viewing porn, the less critical men are of the institution of marriage. Forty-nine (49) percent of the lightest porn users “strongly disagreed” with a statement suggesting that “marriage is an outdated institution” (and an additional 26 percent simply “disagreed” with it), compared with 14 percent of the heaviest porn users.

Of course, correlation doesn’t mean causation, and I’m not suggesting causation here. 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?) Still, we should consider alternative explanations. What might predict both porn use and support for new family forms? Religion? Politics? While religiosity indeed matters for perceiving marriage as outdated, it does little to alter the stable link between porn use and same-sex marriage support. The same is true of political affiliation. It matters. It just doesn’t weaken the association between porn use and supporting nontraditional family forms.

In the end, contrary to what we might wish to think, young adult men’s support for redefining marriage may not be entirely the product of ideals about expansive freedoms, rights, liberties, and a noble commitment to fairness. It may be, at least in part, a byproduct of regular exposure to diverse and graphic sex acts.