By Philip Uwaoma
Having sex because you genuinely want to and having sex because you are worried about upsetting your partner are two very different experiences. Yet, researchers say the second situation may have a deeper explanation than simply trying to keep a boyfriend, girlfriend, husband, or wife happy.
A new study published in the journal Evolutionary Psychology suggests that fear of a partner cheating could be the strongest reason some people agree to have sex even when they are not particularly interested.
The research, titled Who Engages in Duty Sex? Infidelity Concerns and Mate Value Discrepancies, was conducted by F. Sid Dougan, Kate B. Metcalfe, and Cindy M. Meston, researchers affiliated with the University of Texas at Austin.
Published online on October 15, 2026, the study examined whether people engage in what researchers call “duty sex” as a way of protecting their romantic relationships from possible breakups or infidelity.
Dougan explained the thinking behind the research, saying: “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.”
Why Some People Have Sex Even When They Are Not Interested
Duty sex describes sexual activity motivated by obligation rather than personal desire. Someone might agree to intimacy because they want their partner to feel loved, avoid an argument, prevent emotional distance, or reduce the possibility of being abandoned.
Previous research has explored these motivations, but Dougan and his colleagues wanted to investigate whether there could be an evolutionary explanation for the behavior. Their theory was that having sex out of obligation could function as a form of mate retention, meaning an attempt to keep a romantic partner from leaving or becoming interested in someone else.
The researchers recruited 252 sexually active adults in the United States, comprising 176 women and 76 men. Participants were between 18 and 24 years old, and most identified as heterosexual. Their relationship experiences varied considerably. Some had only recently started dating, while others had been with their partners for as long as 84 months, or seven years.
Participants answered questions about their backgrounds, sexual experiences, relationship status, and how frequently they had sex to prevent their partners from becoming angry, losing interest, falling out of love, or leaving them.
The researchers also examined three possible influences: perceived infidelity risk, differences in how participants rated their own attractiveness or desirability compared with their partners, and neuroticism, a personality trait associated with emotional instability and heightened anxiety.
Fear of Infidelity The Biggest Motivation
The findings revealed that fear of a partner being unfaithful was the strongest predictor of duty sex among the factors examined.
Both men and women reported engaging in the behavior more frequently when they believed their partners might cheat. Researchers suggested that someone who suspects their partner could become interested in another person might feel pressure to maintain sexual intimacy to reduce the chances of losing the relationship.
The researchers described this as a possible evolutionary mate-retention strategy. In simple terms, someone might agree to sex because they believe refusing their partner could create dissatisfaction, encourage infidelity, or eventually lead to a breakup.
Interestingly, women and men reported similar levels of duty sex. The average scores were 5.24 for women and 4.76 for men, on a scale ranging from four to 20. Neither the overall frequency nor the relationship between perceived infidelity risk and duty sex differed significantly between the sexes.
Another finding involved perceived attractiveness or desirability. People who considered themselves less desirable than their partners reported more duty sex overall. This association was statistically significant among women when researchers examined the sexes separately, although the researchers cautioned against concluding that the relationship was exclusive to women.
Neuroticism was another contributing factor. Participants with higher scores on this personality trait reported more duty sex, potentially because people who are more sensitive to rejection and relationship insecurity may feel greater pressure to keep their partners satisfied.
The study also found that people in committed relationships reported more duty sex than those casually dating. However, the length of a relationship did not significantly influence the behavior.
Researchers Warn Against Sweeping Conclusions
Despite the findings, the researchers stressed that duty sex was generally uncommon among participants. Most reported doing it infrequently, meaning the study does not suggest that most couples regularly have sex out of obligation.
There are also important limitations. The research relied on participants describing their own experiences, rather than researchers independently observing their relationships. Its 252 participants were predominantly young university students, with considerably more women than men.
The study was also cross-sectional, meaning it examined participants at one point rather than following their relationships over several years. Consequently, it cannot establish that fear of infidelity directly causes duty sex.
Importantly, the researchers acknowledged that having sex out of obligation does not necessarily produce the same outcome for everybody. While it might create temporary closeness for some couples, it could generate resentment and reduce sexual satisfaction for others.
They also called for future research to distinguish between people who reluctantly agree to sex to avoid conflict and those who actively initiate intimacy because they want to strengthen their relationships.
The authors concluded: “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.”
Ultimately, the findings offer an interesting perspective on why people sometimes have sex without feeling particularly interested. However, evolutionary explanations should never be mistaken for an obligation to provide sex. Consent, personal boundaries, and mutual willingness remain essential in every relationship.
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