Sex out of obligation, or "duty sex", is voluntary intimacy not out of desire but out of a sense of duty: to preserve the relationship, avoid hurting a partner, or avoid a quarrel. A new study published in the journal Evolutionary Psychology examines which factors are associated with this motivation.
Scientists from the University of Texas at Austin surveyed 252 students (176 women and 76 men) aged 18 to 24, with an average age of about 19. All participants had a partner and had had sex in the previous four weeks. About three quarters were in serious relationships, the rest were dating casually; the average relationship length was just under 15 months.
Participants completed an online survey in which they rated the frequency of duty sex (using four items related to fear that a partner would stop loving them, become angry, not want to be with them, or leave), the likelihood of a partner's infidelity, their own attractiveness and their partner's attractiveness, as well as their level of neuroticism, a personality trait meaning emotional instability and a tendency to anxiety.
On average, people rarely had duty sex: on a scale from 4 to 20 points, women averaged 5.24 and men 4.76, with no statistically significant differences between the sexes. All three main hypotheses were confirmed: the higher the perceived likelihood of a partner's infidelity, the more often participants reported duty sex (an average probability of 11% among women and just under 10% among men). Such sex was also more frequent among those who considered their partner more attractive than themselves; this association was statistically significant among women but not among men. In addition, higher neuroticism was associated with more frequent duty sex in both sexes, although the effect was modest.
The authors emphasize that this is a correlational study, meaning it shows a statistical association but does not prove a cause-and-effect relationship. For example, anxiety about infidelity may lead to duty sex, or both may be caused by pre-existing problems in the relationship. In addition, the sample included only young students, so the results may not extend to older age groups or to spouses with long-standing relationships. The scientists also did not measure emotional abuse or manipulation in relationships.
"Sex is not always motivated by a desire for physical or emotional pleasure," says lead author F. Cid Dagan. "Our results show that one reason is to prevent a partner from leaving." At the same time, he cautions against interpreting the findings as a recommendation: explaining the evolutionary function of a behavior does not mean that people should behave that way.