Men and women report similar levels of “duty sex,” and similar reasons behind it

People have sex for many reasons beyond physical pleasure or having children, and sometimes those reasons involve a sense of obligation. A new study published in Evolutionary Psychology suggests that individuals who worry their partner might cheat, who see their partner as a more desirable catch than themselves, or who experience higher levels of emotional instability tend to report having sex out of duty more often. The findings are consistent with the idea that obligation-based sex may function as a strategy to keep a romantic relationship intact when people sense it might be at risk.

“Duty sex” refers to consensual sexual activity motivated by a feeling of obligation rather than personal desire. People typically engage in duty sex to maintain their romantic relationship, protect their partner’s feelings, avoid an argument, or prevent their partner from leaving. While this behavior is related to the broader psychological concept of sexual compliance, which covers any consensual sex that a person does not actively desire, duty sex specifically describes encounters driven by a sense of duty to one’s partner.

Although engaging in sex out of obligation is relatively common in romantic relationships, it often comes with emotional drawbacks. Prior research has linked duty sex to lower sexual satisfaction among women, and sexual satisfaction tends to go hand in hand with relationship satisfaction and well-being. For instance, a study covered by PsyPost in 2024 found that women with a history of nonconsensual sexual experiences were 35 percent more likely to report frequent duty sex and experienced higher levels of sexual pain and lower sexual satisfaction than women without such histories.

To better understand what drives people to have sex out of obligation, F. Sid Dougan, a doctoral candidate in evolutionary psychology in the Buss Evolutionary Psychology Lab at the University of Texas at Austin, teamed up with Kate B. Metcalfe and Cindy M. Meston, who conducted that 2024 study, to examine the behavior from an evolutionary perspective.

“My colleagues, Kate Metcalfe and Dr. Cindy Meston, were already doing great work investigating Duty Sex from a clinical perspective, and they kindly invited me to share my thoughts on the subject,” Dougan told PsyPost. “Some past research had looked at certain factors that are associated with greater engagement in Duty Sex, but what I thought was missing from the puzzle was ‘why’ people engage in Duty Sex. To an Evolutionary Biologist/Psychologist like me, this means asking questions about ultimate evolutionary function – that is, 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.”

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From an evolutionary perspective, losing a partner would have carried steep costs for our ancestors’ chances of passing on their genes. Evolutionary psychologists argue that this pressure favored what they call mate retention tactics, which are behaviors aimed at keeping a partner invested in the relationship and preventing a breakup.

These relationship-preserving tactics generally fall into two categories. Cost-inflicting behaviors attempt to stop a partner from leaving by lowering their self-esteem or limiting their social options through tactics such as insults, putting down rivals, or even violence. Benefit-provisioning behaviors, on the other hand, aim to make the relationship more rewarding by showering a partner with gifts, affection, or compliments. The authors of the new study proposed that duty sex acts as a benefit-provisioning tactic, using sexual access to keep a partner satisfied and committed when the relationship feels threatened.

If duty sex is a tool for holding onto a mate, people should be more inclined to use it when they sense their relationship is in danger. One major threat to any romantic partnership is infidelity, which frequently leads to breakups. Another potential threat is a mismatch in what psychologists call mate value, which is a person’s overall desirability as a romantic or sexual partner based on traits like attractiveness, status, and personality. When someone believes their partner has a higher mate value than they do, they may worry that their partner will eventually leave them for a more desirable alternative.

Individual personality traits can also shape how people respond to relationship insecurities. Neuroticism is a core personality trait characterized by emotional instability, anxiety, and a tendency to experience negative emotions. People who score high in neuroticism tend to be especially sensitive to signs of rejection and worry more about losing their partners. Because prior work on duty sex focused mostly on women, Dougan and his team wanted to test whether infidelity fears, mate value gaps, and neuroticism predict duty sex across both men and women.

To test these predictions, the researchers recruited 252 sexually active university students between the ages of 18 and 24, with an average age of about 19. The sample included 176 women and 76 men who were all currently dating at least one partner and had engaged in vaginal, anal, or oral sex within the past four weeks. About three-quarters of the participants were in committed relationships, while the rest were casually dating, and the average relationship length was just under 15 months.

Participants completed a 45-minute online survey that measured their sexual motives, relationship perceptions, and personality traits. To measure duty sex, the researchers used a four-item questionnaire asking how often participants had sex out of fear that their partner would stop loving them, get angry with them, not want to be with them, or leave them. Responses were totaled on a scale ranging from 4 to 20, where a score of 4 meant the participant almost never or never had sex for any of those obligation-based reasons.

To gauge infidelity concerns, participants estimated the percentage likelihood, from 0 to 100 percent, that their partner would engage in five behaviors with someone else: going on a romantic date, kissing, having a one-night stand, having a brief affair, or having a long-term affair. Participants also rated their own overall desirability as a partner and their partner’s desirability on a 7-point scale, allowing the researchers to calculate the discrepancy between the two scores. Finally, participants completed a brief personality assessment to measure their levels of neuroticism.

Overall, most participants reported engaging in duty sex rarely. On the 4-to-20 scale, women averaged a score of 5.24 and men averaged 4.76, and the researchers found no statistically significant difference between men and women in how frequently they engaged in duty sex overall.

That lack of a gap between men and women was unexpected for Dougan. “A big difference between men and women across cultures is that men have much higher sex drives than women on average,” he explained. “Therefore, engaging in sex with a male romantic partner might be an especially effective mate retention tactic for women, but less so for men with female romantic partners, given women’s lower sex drives. For this reason, I thought that women might engage in more Duty Sex than men on average.”

When looking at the combined sample of men and women, all three of the researchers’ main predictions were supported. Participants who perceived a higher probability that their partner might cheat reported engaging in more duty sex, a pattern that held true when analyzing women and men separately. On average, women estimated an 11 percent chance of partner infidelity, while men estimated just under 10 percent, and higher estimates tracked with higher duty sex scores.

“Sex isn’t always motivated by desires for physical and emotional pleasure,” Dougan said. “People have sex for all sorts of reasons, and our findings suggest that one of these reasons is to prevent their romantic partners from straying elsewhere.”

These findings align with research covered by PsyPost in 2025, which found that experimentally triggering fears of a partner cheating increased jealousy and made people more likely to use both affectionate and controlling mate retention behaviors over the following month. While that earlier study examined broad relationship maintenance behaviors following an experimentally induced threat rather than obligation-based sex specifically, both studies link concerns about unfaithfulness to efforts to preserve a relationship.

Perceiving oneself as less desirable than one’s partner was also associated with higher duty sex scores across the combined sample. When the researchers analyzed the sexes separately, this link was statistically detectable among women, with duty sex increasing most noticeably among women who viewed themselves as substantially less desirable than their partners. While the association was not statistically significant within the male group alone, a direct statistical comparison between men and women showed no significant difference in how mate value gaps related to duty sex across the sexes.

This pattern is consistent with recent work on how desirability gaps shape sexual behavior. A study covered by PsyPost earlier this year found that women who view their partner as more desirable than themselves report a stronger drive to sexually satisfy them, which was indirectly linked to initiating sex more often, performing oral sex, and faking orgasms.

Similarly, a 2025 study covered by PsyPost found that men who see themselves as having lower mate value than their partners perform oral sex more frequently, a link explained by a stronger motivation to keep their partners sexually satisfied. Although those two studies focused on specific sexual acts driven by a desire to please a partner rather than sex motivated by obligation, they similarly suggest that feeling outmatched by a partner is linked to using sex as a relationship maintenance strategy.

Personality also played a role in the new study, as both men and women who scored higher in neuroticism reported engaging in more duty sex. This association remained present even when accounting for infidelity fears and mate value discrepancies, suggesting that neuroticism is linked to duty sex beyond what those relationship worries explain. However, the researchers noted that the size of this effect was modest, meaning that duty sex scores rose only slightly across the spectrum of neuroticism when other factors were held constant.

The researchers also looked at whether relationship length and commitment level were linked to duty sex. How long a couple had been together was not statistically related to duty sex for either men or women. Being in a committed relationship rather than casually dating was linked to more duty sex in the combined sample and among men, which the authors suggest may reflect the higher stakes of losing a partner when people have more invested. However, the difference between men and women on this measure was not statistically significant, and far fewer participants were casually dating, so the authors advise caution in interpreting this pattern.

Together, the main statistical model accounted for about 29 percent of the variation in duty sex scores across the sample.

“I think the practical significance of our findings is that Duty Sex shouldn’t automatically be viewed as something negative or dysfunctional,” Dougan noted. “We often assume that people should only engage in sex when they’re experiencing sexual desire, but sexual behavior can serve functions beyond immediate sexual gratification. Consensually engaging in sex to strengthen bonds within a romantic relationship might be a perfectly understandable response to the possibility of losing a valued partner. Our findings will hopefully encourage people to think about this behavior in terms of what motivates it, rather than simply assuming it’s always a problem.”

There are a few things to keep in mind when interpreting these results. Average duty sex scores sat very close to the minimum possible score of 4, so most participants rarely had sex out of obligation. The results indicate that when duty sex does occur, it tends to show up among people experiencing heightened relationship insecurities or emotional instability.

Dougan also cautioned against reading the findings as advice. “Natural selection works in the currency of reproductive success, not happiness or ethical conduct,” he told PsyPost. “Therefore, I really want to emphasize that explaining why a behavior might have evolved is not the same as saying that people ought to engage in it. Our study does not imply that people who aren’t experiencing sexual desire should still have sex with their romantic partners simply because doing so might help maintain their relationships.”

Because the study surveyed participants at a single point in time, it cannot establish cause and effect. For example, while worrying about infidelity might lead someone to have sex out of obligation, it is also possible that preexisting relationship problems cause both infidelity fears and duty sex simultaneously. In addition, the sample included only 76 men compared to 176 women, which gave the researchers less statistical power to detect smaller effects among men and makes it harder to draw firm conclusions about potential differences between the sexes.

The reliance on young university students in relatively new relationships also means the findings might not apply to older adults or married couples who have been together for decades. Nor did the researchers measure whether participants were experiencing emotional manipulation or relationship abuse. If an abusive partner intentionally insults someone to make them feel undesirable and replaceable, that manipulation could artificially inflate the gap in perceived mate value and pressure the victim into having sex out of fear or obligation.

Some of the measures were also fairly limited. Neuroticism was assessed with only two questions, which showed modest statistical reliability. The four duty sex questions focused entirely on fear-based motives, such as worrying a partner will get angry, lose feelings, or leave. That focus means the measure does not capture sex driven by a calmer, proactive sense of duty, and its overlap with worries about a partner straying could strengthen the apparent link between the two.

Future studies could track couples over time to see whether duty sex actually works as a strategy to prevent breakups, or if it breeds resentment and lowers satisfaction in the long run. The authors also suggest that future work should separate passive duty sex, where someone goes along with a partner’s request for sex to avoid a fight, from active duty sex, where someone intentionally initiates sex to keep their partner happy and secure.

“Looking forward, I’d like to conduct studies that distinguish between what I call ‘active’ and ‘passive’ Duty Sex,” Dougan said. “These two forms likely have very different motivations and consequences, in terms of individual wellbeing and relationship stability. Exploring this could provide valuable insights into understanding when Duty Sex might be beneficial or harmful to individuals and their relationships, and how best to address it in clinical settings.”

The study, “Who Engages in Duty Sex?—Infidelity Concerns and Mate Value Discrepancies,” was authored by F. Sid Dougan, Kate B. Metcalfe, and Cindy M. Meston.