Why Sexual Desire Is So Important to a Relationship

Sex is important for maintaining happy romantic relationships. You don’t have to rely on complicated research methods to know that. You may ask people directly why they have sex and learn that they often have sex to strengthen their relationships¹. They also act accordingly. For example, when experiencing intense passion for a partner and satisfying sex, people are likely to express affection for this partner and to have positive feelings about their relationship^2,3. Even merely fantasizing about having sex with current partners predicts actual engagement in behaviors that improve the relationship, such as expressing love for the partners or complimenting them⁴ (Read more here).

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Sexual desire, however, tends to decline over time, with many couples failing to maintain sexual fulfillment in their long-term relationships⁵. Sometimes this decline in desire indicates broader relationship problems. In our recent research⁶, we propose that sexual desire serves as a gauge of a partner’s value as a mate that ensures that only relationships with valued partners will be sustained. Specifically, desire (or lack of) may either foster a relationship with a valued partner or reduce investment in a relationship with a partner who no longer seems suitable.

To test this possibility, we conducted five studies that examined whether experiencing sexual desire for one’s partner increases the likelihood of engaging in behaviors that help maintain a satisfying intimate relationship over time (e.g., sacrificing to benefit the partner). We also explored whether perceptions of partner mate value explain why desiring this partner motivates enacting such behaviors.

In the first and second studies, romantically involved participants relived an activity they experienced with their partner, which was either sexual or non-sexual. Then, participants rated their desire to do something that would make their partner happy (Study 1) or disclosed a recent personal event to their partner during a videotaped face-to-face interaction (Study 2). Judges who watched these interactions evaluated the partner’s behavioral expressions of responsiveness to the discourses (behaviors that signal understanding and caring, such as listening and communicating feelings of affection for the partner).

We focused on the provision of responsiveness because such expressions of caring and concern signal that a partner is willing to invest in the relationship and can be counted on to support the other partner’s needs. We found that experiencing sexual desire for a partner led to an increased desire to do something that would make this partner happy as well as to behaving more responsively to this partner’s disclosures.

In our third study, we sought to demonstrate that perceiving partners as valued mates increase the desire for these partners, thereby motivating investment in maintaining the relationship with them. To do so, romantically involved participants recalled an event in which they either highly valued or less valued their partner. Then, participants rated the extent to which they experienced the sexual desire for their partner and marked how many spa treatments (out of 5) they wished to transfer to their partner in case of winning a lottery, which was conducted at the end of the study. The transferred number of spa treatments was used as an indicator of investment in the relationship. We found that recalling an event in which one’s partner was valued increased sexual desire for this partner. Increased desire, in turn, predicted transferring more spa treatments to the partner.

In our fourth study, we explored whether these findings would apply in settings that are more natural. To do so, both members of the participating romantic couples completed a daily diary for three weeks in which they independently recorded their perceptions of their partner’s value as a mate (e.g., “If my partner were single, he would have been romantically pursued by opposite-sex individuals”), their desire to have sex with this partner (e.g., “I was very interested in having sex with my partner today”) and the extent to which their partner had behaved positively toward them on that day (e.g., “My partner behaved thoughtfully toward me today”).

In the last study, we investigated whether our model would extend to sacrificing for the partner, which is another, more costly behavior that signals caring about a partner’s well-being. For this purpose, at monthly intervals over the course of six months, both members of dating couples reported on their partner’s mate value, feelings of passion for their partner, and sacrifices for their partner (e.g., “I often put aside my own interests for the sake of my relationship with my partner”). In both studies, we found that perceiving partners as valued mates predicted desire for these partners, which, in turn, predicted engagement in behaviors that help promote relationship well-being (behaving positively toward partners and sacrificing for them).

Overall, our findings demonstrate that sexual desire functions as a mechanism that encourages investment in partners who are perceived to be worth retaining. Such dynamics, however, may vary over the course of relationships, as the future may carry with it unwanted changes in the way partners are perceived. In the early stages of relationship development, people often disguise their flaws, later gradually becoming inattentive to each other’s needs, for example. Social status, health, physical attractiveness, and well-being may also ebb (and rise) with time.
Declines in sexual desire may be driven, at least in part, by such changes in perceptions of partners’ value that may eventually deter future investment in the current relationship. Couple interventions that focus on the reduction of negative relationship processes that erode the perception of one’s partner mate value can enhance sexual desire and thereby contribute to maintaining the relationship over the long term.

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