A new study out of Arizona State University has some interesting findings on people's self described religiosity as a mating strategy:
This correlation is interesting, but I think you have to be careful on how to interpret the results. It's not saying that being religious makes someone a better mate or more faithful. Rather, these people think that others will view high religiosity more favorably. Religious people generally see religiosity as a "good" trait, so they may exaggerate their beliefs when in a competitive environment.
To probe the relationship between sex and God more explicitly, Kenrick and colleague Yexin Jessica Li presented hundreds of students at their university with dating profiles of highly attractive men or women, then probed them about their religious beliefs. A control group of 1500 students merely filled out the religion survey.
Men and women who looked at attractive members of the same sex reported stronger religious feelings than those who checked out prospective mates or just filled in the survey. They were more likely to say "I believe in God" and "We'd be better off if religion played a bigger role in people's lives.""It's an interesting and surprising phenomenon," says Kenrick, who speculates that people ramp up their belief in a system that tends to enforce monogamy when they're confronted with fierce sexual competition.
For some anecdotal evidence, I know I did this when I was trying to woo a Lutheran in high school. I was still agnostic then, but I would ramp it up to vague philosophical deist around him. I wasn't purposefully trying to deceive him; it was subconscious. But it worked - we ended up dating for nine months.
If you had a bunch of nonbelievers competing for a mate, we may have the exact opposite effect - we'd exaggerate our skeptical thinking because we see that as a "good" trait to have. We may be extra careful about saying something superstitious or making emotional arguments. Or if I was wooing a vegetarian, I probably wouldn't order a steak for dinner and wear a fur coat. It's human nature to modify your behavior in order to make others happy or find a mate, and this study illustrates that religious belief is no different - a behavior subconsciously used to suit your needs in social situations, not necessarily something you believe in for its truth.