The Science Behind Why Monogamy Really *Does* Work

And 7 other sex truths you need to know now.

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Finally—some science you can bring into the bedroom. How often a couple should have sex is an age old question, something we've discussed over and over again. But how necessary is it for a successful relationship? And just what makes a relationship work? We sat down with Amy Muise, Ph.D., a social psychologist who studies sex and relationships, AKA a sexpert (that's sex expert). She published a study in Social Psychology & Personality Science that might just answer these questions once and for all. 

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MC: Just how important is sex in romantic relationships?

AM: It's important! How satisfied people are with their sex lives is linked to how satisfied they are with their relationship overall. For most people, the first year or two of a relationship are the most intense—"the honeymoon period." During this time, couples are more adventurous and interested in doing a lot of sexual things with their partner. You move from that stage to a different one within two years plus or minus six months.

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MC: Is it all downhill from there?

AM: After a period of time in a relationship you sort of form an attachment bond with the person, meaning that you more fully commit to them and you start to feel more secure about the relationship. Passionate love for some couples remains and often stays or dwindles over time whereas companionate love, that security, often increases over time. 

"It's not that people having sex more than once a week are less happy, it's just that the association between well-being and sexual frequency doesn't increase beyond once a week."

MC: You recently published the study "Sexual Frequency Predicts Greater Well-Being, But More is Not Always Better." Can you explain your research?

AM:We looked at well-being, which is assessed by happiness, satisfaction with life and romantic relationship satisfaction, and the frequency of sex. Around a frequency of once a week we see a leveling off. It's not that people having sex more than once a week are less happy, it's just that the association between well-being and sexual frequency doesn't increase beyond once a week.

MC: Did it surprise you that once a week is the magic number?

AM: I suspected after a certain frequency that engaging in more frequent sex would no longer continue to be associated with greater well-being. What did surprise me is that we did this across a number of studies and very consistently we found this same point—once a week.

MC: But how often are couples actually having sex?

AM: Once a week tends to be the approximate average, which I found surprising. The take home message is that it's important to maintain the sexual connection with your partner but you don't have to aim to have sex every day.

"The take home message is that it's important to maintain the sexual connection with your partner but you don't have to aim to have sex every day."

MC: Did this differ between men and women?

AM: The findings were consistent for men and women. It surprises a lot of people because men typically have higher levels of desire than women and want to engage in sex more frequently, but I didn't find gender differences in the associations.

MC:  So, what is the secret to a happy long-term relationship?

AM: People who value how satisfied their partners are and are invested in seeing their partners happy tend to fare well. It's called a partner-focused or relationship motivation to maintain a partner's happiness and a good relationship. There are a lot of reasons to have sex, but the people who pursue sex to enhance their intimacy, for the betterment of their relationship, or to meet a partner's needs maintain higher desire and are more satisfied.  

MC:  Even with this in mind, rates of infidelity are high. Is monogamy realistic for most couples?

AM: Monogamy is an ideal for many couples. When we think about the biology of this, we certainly have these mechanisms built in to attach and bond to another person. In addition to this, it's what we're culturally told should be part of a relationship, especially long-term. The vast majority of couples, whether they're successful at it or not, have some sort of monogamous agreement. There are some couples that have an explicit agreement to be non-monogamous, estimated to be less than 10 percent, which is still significant. It's important to find a partner that wants a same thing and then you can work to have the kind of relationship you want. Non-monogamy can be successful for some couples, it depends on what they want.

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