Surprising fact about ‘duty sex’ revealed — and the real reason couples do it: study

Couples across the US are heeding the call of duty.

A new study seeks to find the evolutionary explanation for “duty sex,” IE couples who are getting it on out of obligation rather than desire.

Previous research has identified myriad factors that contribute to duty sex, including relationship preservation, safeguarding a partner’s feelings, mitigating conflict, or preventing abandonment.

However, this latest study, published in Evolutionary Psychology, aimed to discover the evolutionary benefit of obligatory sex.

“What reproductive advantages might this behavior have provided over our evolutionary history? I wanted to know if duty sex serves an ultimate function, and if so, what that function is,” explained lead study author F. Sid Dougan.

The study, published in Evolutionary Psychology, included 252 participants, 176 women and 76 men, between the ages of 18 and 24.

Most participants identified as heterosexual, and relationship length ranged from just beginning to 84 months.

Participants completed a survey that included questions related to “age, gender, race/ethnicity, education, sexual orientation, current relationship status, number of lifetime romantic and sexual partners, and current sexual activity (vaginal, anal, or oral sex).”

Participants also answered a questionnaire that explored how often they would engage in duty sex to protect their relationship.

Researchers evaluated “perceived probability of partner infidelity, mate value discrepancy, and neuroticism” to predict the likelihood of duty sex.

Results showed that men and women engaged equally in duty sex when they feared their partner would be unfaithful.

Indeed, fear of infidelity was associated with higher rates of duty sex than any other factors.

This is consistent with earlier findings that established couples engage in more “mate retention” behaviors when they perceive greater risk of infidelity or during periods of increased risk such as rough patches or prolonged separations.

Researchers believe that when someone suspects their partner might stray, having sex out of obligation may actually be an instinctive, evolved behavior meant to stop them from leaving.

The study revealed that relationship length had no bearing on the frequency of duty sex for either gender.

Interestingly, the study found that men and women participate in duty sex at the same rate, even though previous research suggests men have higher sex drives.

Researchers acknowledge the study’s limitations, including self-reported data, a small sample size, and participants who were predominantly young and in the early stages of their relationships.

In conclusion, the study authors underscored the importance of situating duty sex within an evolutionary framework:

“This work highlights how behaviors that appear obligation-based may reflect strategic responses to perceived partner loss risk, offering a foundation for future research on the role of sexual behavior in relationship maintenance.”