Religions provide a common moral compass for their believers. For instance, all faiths promote some version of the Golden Rule as one of their major tenets. Many also enforce dietary restrictions in the form of guidelines about what’s appropriate to eat or not and on what occasions. There may also be regulations about clothing, social interactions, and when to work or rest.

Another universal feature of religions around the world is sexual conservatism. All faiths condemn or at least discourage premarital or extramarital , insisting instead that sexual activity is only acceptable within committed and religiously sanctioned unions, most typically between a man and a woman of child-bearing age. The reasoning goes something like this: Sex is about procreation, and so you should only engage in the act if you’re willing to stick around and help your partner raise the children you produce.

Thus, it seems that one function of religion is to enforce conservative attitudes about sex for the purpose of encouraging its members to pursue a lifestyle conducive to raising families. However, Arizona State University psychologist Jordan Moon and his colleagues propose that we may have put the causal relationship between religion and sexual conservatism in the wrong order. That is, instead of religion making people conservative, they argue, people with restrictive reproductive attitudes seek out religion to bolster those values.

Humans vary in the degree to which they pursue short-term versus long-term strategies. Some people have dozens or even hundreds of sex partners during their lifetime, while others remain committed to a single partner until death. In a modern industrialized society, a mixed strategy seems to be the norm. In young adulthood, we may have one or more short-term sex partners before entering into a committed and monogamous relationship. We may also revert to short-term mating if that marriage fails, at least until we find another long-term partner. Psychologists refer to this relative preference for short- or long-term mating as sociosexuality.

Data show a clear link between sociosexuality and , or how serious you are about your religious beliefs. In fact, a number of lifetime sex partners is a very good predictor of church attendance. After all, you’ll find little social support at any church for a promiscuous lifestyle, but if you publicly espouse the attitude that sex is only appropriate within the confines of marriage, you’ll find plenty of people who share your values.

The relationship between sexual attitudes and religious observance is only correlational, so we can’t say for sure which causes the other. It could be, as generally believed, that religious belief leads to conservative sexual attitudes. But it could also go the other way, as Moon and his colleagues propose. Additional data are needed to help us discern the direction of causality’s arrow.

One piece of evidence that Moon and colleagues offer is the observation that women are more likely to be regular churchgoers than men. We also know that women are more likely to espouse a preference for long-term monogamous relationships than are men. According to the argument, a woman seeking a long-term relationship may choose to attend church because she knows she has a greater chance of finding a like-minded mate there that at, say, a bar or a gym. And if she’s already married, she’ll want to bring her husband to church with her so he’ll clearly get the message that thou shalt not commit .

Notice that the preceding argument actually begs the question. That is, it assumes men and women choose to attend church in order to bolster their preference for long-term monogamous relationships. But this is exactly what Moon and his colleagues are trying to demonstrate. So even if the above scenario rings true, it’s really not evidenced either way.

What’s needed is a “third variable” that relates to both religiosity and sociosexuality. One possibility is the issue of trust. Prior studies have shown that religious people are perceived as more trustworthy than nonreligious people. This is true even when the target person is a member of a different religion. For instance, Christians judge Muslims as more trustworthy than atheists. Ironically, even atheists rate Christians or Muslims as more trustworthy than other nonbelievers. These facts demonstrate that the perceived trustworthiness of religious people isn’t due to any sort of in-group .

But where does this trustworthiness come from? One possibility comes from the fact that both Christians and Muslims believe they’ll be punished for their sins, and this motivates them to lead honest lives. Keep in mind that we’re talking about perceptions of trustworthiness, not an actual degree of honesty—whether believers are indeed more trustworthy than nonbelievers is a question for another study.

Since we all know people who profess religious faith but lead lives of sin, maybe church membership alone isn’t an especially reliable indicator of trustworthiness. Instead, what we want to see is a commitment in action. And what greater commitment do we make in life than entering into a monogamous relationship for the purpose of raising a family? While confer many long-term benefits, in the short run they’re often exceedingly . There’s hardly a spouse alive who hasn’t felt the temptation at some point to walk out the door or just not go home. And yet we persevere in the commitment for decades. Clearly there is an honest signal of dependability and trustworthiness.

In an experiment, Moon and colleagues presented research participants with one of four scenarios, disguised as a social media profile. In two of the scenarios, the person was described as “Christian,” and in the other two as “nonreligious.” Likewise, the person was described as wanting to get married and raise a family in two of the cases, and as wanting to remain single and “play the field” in the other two. (In other words, the researchers crossed religiosity with sociosexuality.) Participants were asked to rate their perceptions of the person on a number of characteristics, including trustworthiness.

If religion confers trust, the Christian should be judged as more trustworthy than the nonbeliever, regardless of sociosexuality. Instead, the researchers found that both the Christian and the nonreligious person were equally trusted—as long as they said they wanted to get married and raise a family. Likewise, when the person said they wanted to play the field, they were judged as untrustworthy, whether they were religious or not.

These results indicate that sociosexuality is a more important indicator of trustworthiness than religiosity. The findings also suggest that people trust religious believers more than nonbelievers because they infer that churchgoers are more likely to commit to marriage and family, the litmus test of reliability. Furthermore, it’s not a religion’s moral code in general (prohibitions against , stealing, and so forth) that make its believers appear more trustworthy but specifically its injunctions against premarital and extramarital sex.

Moon and colleagues offer one more piece of evidence that people seek out religion as a means of bolstering their chosen long-term mating strategy. The researchers note that church attendance in adulthood follows an inverted U-shaped curve, with the bulk of attendees being married couples with children. Parents will say they do this because they believe religious instruction is good for the kids, but moms and dads benefit as well. At church, they meet other couples who are facing the same stresses in and the same strains in marriage that they are. They learn they’re not alone or unique, and the social support they receive in religious fellowship can help mend the cracks that inevitably creep into any long-term relationship.

Both religiosity and sociosexuality are complex human phenomena which no doubt have mutual influences on each other. Religions around the world preach the of committed monogamous relationships. Those with a preference for a long-term mating strategy will find such sermonizing appealing and joining a fellowship of like-minded souls validating. Meanwhile, those who are inclined toward a short-term mating strategy will find little affirmation in church. Rather than convincing people of the value of committed sexual unions, religions attract members who already favor but seek validation for their belief.