If researchers seem a bit, well, voyeuristic with regard to people's sex lives, there's good reason for it: In heterosexual marriages, the happier people are with the sexual lives, the happier they are with their relationships. And if you want to know how much a newlywed couple is enjoying and having sex — and really, who doesn't — then look at their personalities.

Specifically, look at the wife's personality. If she's super curious about life and easy to be around, it's more likely that the couple is getting laid, or so says a new study. The man's personality, on the other hand, doesn't seem to have much of an effect on how often the couple has sex.

In a new study of 278 heterosexual newlywed couples, Florida State University psychologists Andrea L. Meltzer and James K. McNulty asked participants to keep daily diaries — a more reliable way of measuring sexual frequency than asking people to retrospectively remember — and take a personality test of their so-called Big Five personality traits, the most agreed-upon personality model.

Unlike the Myers-Briggs and its peers, the Big 5 has repeatedly held up in empirical testing. The traits are conscientiousness, or how likely you are to be on time to meetings and reply to emails; agreeableness, or how eager you are to please people; openness to experience, or how much you crave adventures; neuroticism, or how much you react to the sundry difficulties of life; and extraversion, or how much you want to hang out. For a book-length survey, read Me, Myself, and Us: The Science of Personality and the Art of Well-Being, by Brian Little.

The researchers asked three different samples of newlyweds, mostly aged between their mid-20s and early-30s, to keep the diaries for two weeks, writing down what they did that day. They were asked to report whether they had sex every day, and, if they did, how satisfied they were with it on a seven-point scale. The couples averaged having sex on three to four days in that two-week period.

Previous studies have found that men want and initiate sex more than women, the authors say, prompting women to be labeled as "the 'gatekeepers' of sex within relationships." Traditionalist as this idea may be, the authors wrote that their own findings support it as well: The higher a wife rated on openness to experience or agreeableness, the more often the couple had sex. The husband's personality, on the other hand, was not a predictor of sexual frequency.

Sexual satisfaction was another story. In this case, both partners' personalities mattered. For men and women, higher levels of neuroticism were linked with lower levels of satisfaction. Intriguingly, husbands' openness was negatively correlated with satisfaction, while for wives it was the opposite. And it was the individual's personality — not their partner's — that correlated with satisfaction.

But, as the authors note, this study — comprising 14 days for couples who are perhaps still in the honeymoon phase — should not be taken as representative of all couples in all stages of relationships of all time. Plus, it would also be useful to get more queer relationships in the mix, and Meltzer told Science of Us that future research would benefit from examining them. Also, since so much of sexuality is informed by culture and upbringing, it would be fascinating to see how people in more "liberated" areas like New York or San Francisco compare with those in more conservative enclaves.

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But no one really knows how much sex a "happy" couple — married or not — is "supposed" to have. "What I can say is that, in a number of studies of newlywed couples (most of whom are extremely happy), couples report having sex approximately every three to four days," Meltzer said in an email. "I am not sure, however, how frequently 'happy' couples who have been married longer (or even dating couples) have sex."

Indeed, when one team of researchers asked couples to double the amount of sex they were having, it turned sex into a chore for the participants — and they liked it less.