Paul and Leah met a decade ago, both in their mid-twenties, on a blind date that was truly blind. Social media and smart-phone selfies were not yet a big thing, and they lived in different cities. After a marathon call lasting three hours, Paul got on a plane and met Leah in the lobby of the department where she was working on her master’s degree. He still remembers the elevator door opening, the green corduroy skirt she was wearing, their eyes meeting for the first time. After dinner at a nearby restaurant, they went back to Leah’s place to watch a movie she needed to see for a class. They didn’t get to the second scene. A few minutes in, Leah made the first move. (Several names have been changed in this story to protect the anonymity of sources.)

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Three months and three hot and heavy visits later, they were living in the same city. Married a year later. They both remember those early days as blissful and lusty.

Fast-forward eight years. Paul still wanted sex as much as ever, but Leah hardly wanted it at all. “I’m more demanding, more interested than she is, and need more than she does,” he said. “But if you have to ask for it, beg for it, or fight for it, it takes the fun out of it.” The reasons for the change will be familiar to any couple that stays together long enough—the birth of a child stealing sleep and free time, a stressful family medical crisis, up and down careers creating mortgage worries.

According to a 1995 paper by US sociologist Vaughn Call that drew on the National Survey of Families and Households—which 13,000 individuals completed in the late ’80s—the average frequency of intercourse drops by nearly half during the first year of marriage. After that initial dip, the decline correlates with age. Couples typically have sex eight to twelve times a month in their twenties and six to eight times a month in their thirties and forties. There’s a dearth of such data in Canada, but a 2011 Canadian Living Intimacy Survey found that while 53 percent of us would like to have sex a few times a week, the majority—39 percent—are making do with a few times per month. For 23 percent, it is even less. As Call’s study noted, “Some couples stop having sex or have it very infrequently, and this cessation is not limited to couples over the age of 60.”

Paul and Leah never reached complete abstinence—at least, not for more than a few weeks—but the slowdown caused friction and threatened their marital harmony. “We kept circling around the same discussion,” Leah said. “He was always taking it personally that I wasn’t getting turned on and wasn’t interested. I was always saying, Listen, we’ve got little kids. I’m tired. It’s not about you. I’m not fired up in general. And I’m not thinking about other guys.” She paused. “But it’s hard to not take it personally,” she admitted. “I could see it was hurting him.”

Eventually, they came to an agreement. Paul wouldn’t expect Leah to actively desire sex, but he would still make demands and even be a little pushy about it. Her concluding proposition to Paul was this: “I’m asking you and giving you permission to take the lead and to not feel bad about it. Don’t feel you’re being too aggressive.’ ”

University of Toronto psychologists Emily Impett and Amy Muise call such an arrangement a form of sexual sacrifice: that is, having sex with your partner when you’re not in the mood. Unlike many of their colleagues, though, they see this as a good thing.

“One of the greatest sources of conflict in relationships is around sexuality, and it’s something we don’t know very much about,” says Impett, who founded the university’s Relationship and Well-being Lab (RAWLab for short) in 2010. The trim thirty-nine-year-old is one of the few social psychologists with a background in the study of both relationship theory and sexuality. “I don’t mean you’re getting into a heated brawl, but just conflicts of interest. How do couples navigate that? ” Her collaborator, Muise, also combined the two fields in her doctoral work at the University of Guelph, in Ontario. She joined the lab as a post-doc in 2011. Together, they are interested in how we negotiate our sense of self within relationships, and how our most intimate connections affect our general level of happiness. They are also at the forefront of research into how to keep desire alive in a long-term commitment.

I first met the researchers in January. At the time, Impett, who bears more than a passing resemblance to the actor Sarah Polley, and Muise, a stylish thirty-two-year-old with a heart-shaped face made for television, were running their lab out of a notably unsexy two-storey, temporary building on the university’s Mississauga campus. A series of nondescript offices led down a long hallway of grey carpet; at one end, there was an observation area—an office with cameras on the ceiling and a one-way mirror. It had seen very little action. Instead, information flowed directly from bedrooms to the lab’s computers in the form of thousands of questionnaires and daily logs.

The majority of research has had a “laser focus on risk avoidance and prevention,” as Impett and Muise noted last year in the American Psychological Association’s debut handbook on sexuality. Sex has more often been studied within the context of disease, death, and coercion—necessarily important places to start, but there are compelling reasons to look at it from a positive angle, as well.

Sexual satisfaction is strongly linked with overall mental and physical health, according to the scant research available. Two long-term studies—one of more than 2,000 Taiwanese men and women older than sixty-five, and another of 3,000 Welsh men between forty-five and fifty-nine—found individuals who were more sexually active had lower mortality rates. A Swedish study found that men over seventy who were still having sex were less likely to die in the ensuing five years. (All three studies controlled for overall health to neutralize the fact that healthier people might have more sex.) Meanwhile, social psychology studies have found that people in committed romantic relationships are happier and healthier, and that sexual satisfaction helps keep people together for longer.

Despite such evidence, researchers are only now exploring the most basic questions about how sex functions in relationships. Impett and Muise are especially interested in the role that sexual sacrifice could play in successful long-term monogamy: “When the desire is high for both of you, it might feel like you’re always making this autonomous decision to have sex,” said Muise. “But over time, it’s unlikely that you’re going to always be in the mood at the exact same time. Compromises will have to be made.” This observation has led to one of the most controversial questions she and Impett have pursued: Should the decision to have sex always default to the low-desire partner?

Martha, a woman in her late thirties, recently ended a relationship with a man she’d been with for several years—because they were no longer having sex. She still wanted to, but he didn’t. When problems arose between the two partners, he would withhold physical affection. “It made me feel like there was no baseline of trust,” Martha said. “I wanted him to think, We’re having a difficult time, but I can still trust you and connect on a non-verbal level.”

When enough of those problems had accumulated, he stopped making romantic overtures altogether. “In the last year of the relationship, he did not initiate once,” she said. “I could understand if it was a phase, but that was too much.”

Martha tried to become the initiator, but was met with rejection. “It’s embarrassing when you start making out with someone and they’re like, ‘No,’ ” she said. “It’s embarrassing to have read them wrong and it’s embarrassing that you made your desire transparent.”

But Martha wasn’t sure she wanted pity sex, either. “I feel when people have desire for each other, it blinds them to the imperfections of the other person. You can feel less self-conscious when you’re having sex,” she said. “But if the other person isn’t aroused when they’re getting me off, I feel grotesque. If you think of a vagina out of context, on the subway, it’s kind of alarming and odd and a weird thing. But if you have desire, then the vagina is an interesting and hot thing. If you sense the other person isn’t into it, you wonder, What are you seeing right now? ”

Until Impett and Muise came along, most researchers in the field explored only the negative outcomes of sexual sacrifice. They use a different term: sexual compliance. If someone is having sex when they don’t really want to, the theory goes, a manipulative partner may have primed them to fear saying no. They may be suffering from low self-esteem. Going through with it leads to an entrenchment of the problem.

Impett and Muise acknowledged the existence and dangers of compliance, but wondered whether it might not be the whole story. Communal theory—established in social psychology in the early ’80s—suggests we benefit from being altruistic in our relationships instead of viewing them as a tit-for-tat exchange of resources. The interdependence theory of the ’90s observed that we can sometimes feel better about ourselves when we take a hit for our partner. But no one had applied these ideas to the bedroom. Impett and Muise wanted to know: Could a tendency to place a partner’s carnal needs first actually boost levels of desire in the partner doing the sacrificing?

Their answer, published last year in the journal Social Psychological and Personality Science, was a qualified yes. “Popular perception suggests that marriage (or a long-term partnership) marks the end of sexual desire in a relationship,” they wrote in a paper entitled “Keeping the Spark Alive.” But, they added, “Not all couples experience these declines…and some are able to maintain strong feelings of passion and desire for several decades.” Such couples, they argued, have higher levels of something they called sexual communal strength, meaning they were more likely to put a partner’s needs first.

RAWLab’s study followed forty-four heterosexual couples over the course of several months. (Their work has also included same-sex couples, just not yet enough to be statistically significant or to compare with heterosexual couples.) The researchers began with questions that would reveal how communally oriented their subjects were. How likely are you to sacrifice your own needs to meet the sexual needs of your partner? How far would you be willing to go to meet his or her needs? How easily could you accept not meeting your partner’s needs? Cross-referencing the answers with reports on daily interactions—and increased or decreased feelings of desire and relationship satisfaction—allowed them to create a portrait of what kind of person is having the best sex in marriage. The study, now just one of several run along similar lines, confirmed its hypothesis: those who put their partners’ needs first maintained a higher pitch of desire over the course of the experiment. This was true regardless of gender, age, how long they’d been in the relationship and how happy they were with it, and whether or not they had children. Moreover, these people were also more likely to report being more sexually satisfied and happier in their relationship four months later.

Impett and Muise suspect sexual communal strength could point the way to that holy grail of the long-term relationship—everlasting sexual interest. If so, this challenges the modern Western assumption that the individual will and wish are king. In the context of the brand of individualism that we live with today, passionate love is thought of as something we feel, and should feel before acting. Impett and Muise’s research tells a different story: love is something we do, and it is in the process of giving that we feel it.

Linda and Frank are a married couple in their fifties. They met when Linda was in her late twenties and recently divorced. On the rebound, the relationship started off as just physical, but over time she and Frank began dating in earnest. Next year, they celebrate twenty-five years together.

“When we have fights, we don’t ever let it get in the way of sex,” said Frank. Linda said she doesn’t understand women who withhold sex from their husbands. “I remember being at the gym, in the change room, and hearing these shocking conversations. The women would bitch about their partners always wanting sex, or how they thought it was really funny to withhold it as a punishment. One time I confronted them and asked, ‘Don’t you miss sex? Aren’t you punishing yourself when you do that? ’ One of them said, ‘Oh, my vibrator satisfies me better than my husband does.’ ”

Linda is happy to give even if she’s not turned on: “I may have a lot on my mind, but it doesn’t mean I don’t want him to have pleasure.” Frank also taught her, she said, to let him return the favour. “For most women who constantly give, it’s not easy to receive. But when someone genuinely wants you to receive, no matter whether they’re in the mood, it’s a gift. What you can give them back for that is receiving without guilt.”

In the last few years, the couple has had to transition to a new, more challenging phase of their sex life: she’s been going through menopause and he’s been having a harder time getting erections. Keeping intimacy a priority as they always have, Linda and Frank have had to work through those changes and make some adjustments. “If you don’t talk about it, your partner will think it’s them,” Linda said. Frank added, “You have different equipment that you’ve got to work with now.” Even though Linda understood the changes in her husband’s function, she still needed the reassurance: “I still would wonder, Are you sure it’s not me? ”

Their strong communal bond may also be the reason they were able to weather an affair four years ago, when Linda’s best friend and Frank “crossed a boundary that never should have been crossed.” The couple went to counselling. Throughout, Linda was determined to remain physically close with Frank. “You have to choose to forgive someone, and then really forgive them and let it go,” she said. “Or else get out. It is hard for me sometimes, but he’s punished himself way more than I have wanted to punish him. I don’t think our sex life should have to suffer.”

The suggestion that anyone, but especially a woman, should force herself to have sex with her partner conjures up the old ghost of “wifely duty.” The term refers to a host of things a woman was supposed to do as far back as the Middle Ages, but it’s most often recalled these days when talking about sex.

“It was a woman’s moral and legal duty to submit,” Elizabeth Abbott, a social historian, explains in A History of Marriage. “A husband could take legal action against a wife who managed to withhold sex, but a wife could not lay rape charges against a husband who forced sex on her.” The good wife wasn’t supposed to possess any desire, merely tolerating sex “to satisfy her husband’s sexual needs,” writes Abbott.

Last year, Impett and Muise found themselves entangled in controversy when their work—along with that of several other researchers—was mentioned by Wall Street Journal columnist Elizabeth Bernstein, who profiled a couple that had been struggling with a desire discrepancy. Reasons for their problems were outlined—she’d had a miscarriage early on that affected her libido, and the two had wed before testing their physical chemistry—but the article focused mainly on the scientific evidence of a man’s emotional and physical need to have sex. Bernstein, as well as the couple themselves, suggested this solution: that the woman figure out how to fulfill his want. “For me to feel good about myself, I needed her to have sex with me,” went one of the husband’s more inflammatory quotes. “Otherwise, I thought she didn’t love me.”

The response was swift. The most sarcastic retort came from New York magazine, which referred to the article as “the story of Chris and Afton Mower, high school sweethearts turned Mormon newlyweds whose marriage has improved drastically since Mr. Mower taught his wife that not having sex with him amounts to cruel and unusual punishment.”

Online, Jezebel writer Lindy West argued that making the specific origins of this couple’s problem secondary to the discussion of a male need for sex was deplorable: “When talking about sex, female trauma is not subordinate to male frustration. Men not ‘getting’ enough sex from their chilly wives (as though wives couldn’t possibly want sex, or be justified in not wanting it) has been our oversimplified narrative for generations. Prioritizing men’s sexual issues over women’s is not a revolutionary, maverick stance—it is the status quo dressed up as progressive pablum.”

Sexual coercion remains a real concern. One woman I spoke with described how subtle these negative sacrifices can be. “One time, I was hanging out with this guy, and I was young, and I realized, Oh, he wants sex. And I felt too weird and self-conscious to say no. I decided to give him a blow job and get it over with. It was not a good feeling,” she said. “So many women have had an experience of feeling pressured to do something they didn’t really want to, and those events can’t help but leave an emotional impression: I’m trapped in this guy’s car, and now I have to give him a hand job. Or, he’s my professor, so I have to do something.”

Still, Muise doesn’t believe critics should dismiss the husband’s needs outright. “One of the reasons I think the WSJ article garnered such strong reactions is because any time we think about women engaging in undesired sex, we think about rape and sexual assault,” Muise wrote in a follow-up blog post on Psychology Today:

Certainly, part of this stems from the way that men’s positions of power in many societies have been leveraged to their sexual advantage, but neither the article nor the research more broadly is suggesting that women (or anyone) engage in something that makes them feel violated, or that men (or anyone) have the right to sexual coercion. Instead, I am suggesting that we make room for the idea that sexual needs can be important in a relationship. Given that many couples are sexually exclusive, romantic partners play a key role in meeting each other’s sexual needs.

Muise added the taboo nature of sex in North America can obscure the fact that we do things all the time for our partners when we’re not in the mood: “Had the WSJ article been about giving a partner a back massage when you are not in the mood, or going to a partner’s work event when you would rather stay at home and relax, I doubt it would have been so controversial (regardless of which gender was meeting their partner’s needs).”

Wifely duty is a repugnant notion, sure, but what of a two-way spousal duty? What if our partner’s specific desires around sex are something we should want to fulfill?

Reading this article could improve the sex in your marriage—at least, that’s in line with the hypothesis that Impett and Muise plan to test. The RAWLab team recently won a five-year grant that will (among other things) fund a study in which the researchers explain to a group of couples the benefits of being communally oriented in their sex lives, to see whether awareness of the concept leads them to adopt this strategy.

“If we can get people to construe the self in more interdependent terms,” as Impett and her co-authors wrote in another article, then “we may be able to prevent them from experiencing some of the costs of giving in to a partner to avoid negative outcomes.”

The motivation behind an act of sexual sacrifice is crucial, which is in keeping with previous findings from general sacrifice theory research. Impett and Muise’s work has already demonstrated that having communally oriented sex to achieve a positive “approach” goal (e.g., wanting to give your partner pleasure, or to feel closer to your partner) puts you on the upward desire spiral. But if you don’t score high in communal strength, and if your motivation comes from “avoidance” goals (having sex to get your partner off your back, or succumbing to their needs to avoid upsetting them), you’ll experience what they call “negative outcomes”—a drop in desire.

Although we may not yet know how people can deliberately increase their communal strength, studies outside the sphere of sexuality have already shown it is possible to prime or boost your inclination toward approach-goal motivations. When people are told to think about having a good time with a person they are about to meet, they report a better experience than those trying to avoid having a bad time and making a poor impression. “In the moment, people could focus on what they might like about the sexual encounter: I’ll feel closer to my partner, or my partner will feel really good,” suggested Muise.

Lori Brotto, a psychologist who runs the Sexual Health Laboratory at the University of British Columbia, integrates some of Impett and Muise’s motivation research into her clinical work. In her private practice for couples and monthly group sessions for men and women, she too has observed that avoidance goals usually worsen clients’ problems with chronic low desire. “They may be still having sex, but for bad reasons,” she said. “To avoid a fight. To avoid a partner being grumpy the next week. That fosters resentment.” As part of treatment, she presents clients with a list of eighty reasons to have sex, which she adapted and shortened from University of Texas at Austin researchers Cindy Meston and David Buss. When Brotto nudges clients toward approach-oriented reasons, the response is usually positive: “They’ll say, Okay, that makes sense. I could try that on.”

Not everyone finds trying on reasons to have sex easy, however. Vicki, who joined Brotto’s group in her late-fifties, lost all interest in sex when she entered menopause. The timing was odd because she was six months into a new relationship, when sex is usually easy and flowing. “My body just didn’t respond, almost overnight,” she said, noting that she’d never had any issues before, including in an earlier marriage. The following two years were difficult for the new couple. They still had sex, but it was what she described as “accommodating sex,” with an avoidance goal in mind. “One of my greatest fears was that if I didn’t co-operate—that’s what it feels like in those moments—he would leave me for someone else.”

Vicki didn’t immediately take to the list of eighty reasons to have sex: “As one of the girls in the room said, ‘Why would I want to pretend? If I don’t have desire, why would I have to fake it? ’ ”

A therapist helped her to finally identify a reason to do it—“to be closer.” She craved intimacy, despite her diminished desire. Starting with exercises that involve scheduled daily periods of non-sexual touching, Vicki hopes to work back up to enjoying sex. And at least one of her reasons is a communal one: “I don’t eat meat, but my boyfriend is a meat-and-potatoes guy, so I cook meat regularly for dinner. When you’re in a relationship, it’s not about you all the time. If it’s something that is important and matters to him or that he really likes, why wouldn’t I do that? ”

A week after Valentine’s Day, Impett and Muise gathered in RAWLab’s conference room with the eight graduate and undergraduate students who make up their team. Lisa Day, a twenty-four-year-old Ph.D. candidate, was practising a mouthful of a talk: “To Do It or Not to Do It? How Communally Motivated People Navigate Sexual Interdependence Dilemmas.” Much of the material was familiar to her lab mates: Day noted that 80 percent of the 336 men and women who took part in her study could remember a time in the last month when their partner desired sex and they didn’t. Those who were high in sexual communal strength were more likely to do it when they were not in the mood, and their overall satisfaction with their relationship improved.

But the discussion that followed illustrated how many aspects were still unexplored. Muise wondered aloud what would happen if you flipped the research question on its head: Instead of asking whether a communal partner would have sex when he or she is not in the mood, what about a communal individual respecting a partner’s need to not have sex? And what happens when two communally oriented people with different libidos are in a relationship? “Maybe they will be more accurate in knowing whose need is stronger in the moment,” Muise suggested. “You really want to have sex, and I only kinda don’t want to,” Impett joked.

There was discussion, too, about how to distinguish communal strength from harmful, unmitigated communion—a social psychology term that describes a partner always doing what his or her partner wants, to the exclusion of his or her own needs. And maybe, Impett suggested, there are some circumstances when avoidance goals are okay. A mother of two, she wondered whether the transition to parenthood might be a time when having sex for any reason at all is preferable to letting sexlessness take hold. It was enough to make your head spin.

What about when we do sacrifice ourselves sexually, someone asked. Hide this from our partners? The commonly held notion among social psychologists is that our sense of authenticity will suffer if we secretly sacrifice ourselves, which can lead to conflict and disconnection. Not so for the highly interdependent, according to another RAWLab study. Communally oriented subjects gained self-esteem by protecting their partners by telling white lies. Apparently, we want our partners to want to give us what we need, but if they don’t really want to do that, hiding that fact from us is a good thing for everyone involved. Applying those conclusions to sex is on RAWLab’s long to-do list.

At our first meeting, I asked Impett if she was trying to save monogamy. She demurred, saying she supports open relationships if both partners are in agreement. She’s more interested in finding a way to make our long-term commitments last. (She and her own partner have been together for nine years, and married for more than six.) “People get into a relationship and expect that their desire is going to be high because they’ve finally found this right person, and that they’re going to maintain this desire,” she said. “I think a lot of times when desire declines, people think they’re not with the right person anymore. They get out of the relationship, or have an affair, or start a new relationship. And that’s why we see this serial monogamy. People should be making decisions based on much more information.”

In the conclusion to “Keeping the Spark Alive,” Impett and Muise observed that you can’t very well flex your sexual communal strength unless you first know your partner’s needs. But most of us are more willing to be candid about our preferences with a complete stranger than with the person in our life we’re most afraid of offending—and losing.

For Paul, opening up about his sexuality was key in resolving the deadlock with Leah. Three years ago, he told his wife to get dressed up to go “somewhere sexy.” He’d never been to the Feminist Porn Awards, an annual event in Toronto that’s billed as “the longest running celebration of erotica focused on women and marginalized people.” It blew his mind. “You see lesbians, gays, transgendered people, and people with disabilities—all fucking on the big screen,” he remembers. “Dildos, music, screaming, yelling, cross-dressers. And you see it all in a really friendly environment.”

After the date, he obsessively read everything he could find about the award winners. He learned about Jiz Lee, a gender philosopher and gender-queer performer who lives in San Francisco. Paul was particularly touched by the story of a transgendered man who, at seventeen, felt constrained by the culture of his Texas hometown and ran away to Los Angeles. “It’s not that I’m looking to be a transgendered porn star,” he said. “It’s just cool. It’s inspiring to see people follow their dreams. If a guy in Texas can go to LA and become an award-winning porn star, then I can have a conversation with my wife about my feelings and interests.”

Leah found Paul’s appreciation of queer porn confusing, and they had to talk a lot before either could figure out how it might actually be a good thing for them. “In the end, it was about curiosity and open-mindedness and a healthy sex drive,” Paul said. “Once we got our heads around it, a lot of conversations fell out of that. We started watching some porn together. We’re still pretty vanilla, but it was liberating to have these conversations.”

She remembers the Feminist Porn Awards as less pivotal, but agrees it helped them refresh their relationship. “We’ve shared more, and I think our sex has gotten more personal, more open,” she said. “Dirtier, probably. We have a very good sense of what we like. But it’s a tricky one. There are some things that I know Paul would like me to do more of that I’m not super comfortable with, and I feel some guilt about that.”

Paul had to get over the thought that Leah was sacrificing herself out of pity. He had to remember that she really did want to be intimate and that he could let the rejections roll off his back. “You gotta get it started somehow,” he said. “Then you’re having a little bit more sex. And then all of the sudden, I’m happier. And that makes her happier. And then the sex gets better, then life gets better, then sex gets better, then life gets better.”

Leah doesn’t know if they’re having sex more often, but agrees that the quality has improved. “You need an acceptance on the one hand of a partner’s lowered libido,” said Leah. “On the other hand, there has to be a demonstrated effort to care about the other person.” Her rejections only stick about a quarter of the time now. “We found a way to dispel the feelings of hurt and disappointment,” she added. “It feels more passionate and more loving, and more accepting of what we need.”

* An earlier version of this article quoted a source who said that “Sex columnist Dan Savage is always advising you to do whatever your partner wants, regardless of your own boundaries.” This is a mischaracterization of Savage’s advice. While Savage encourages partners to be sexually generous with one another, he has never said that people should ignore their own boundaries. The Walrus regrets the error.

This appeared in the September 2014 issue.

Micah Toub Micah Toub is the author of Growing Up Jung: Coming of Age As the Son of Two Shrinks, a memoir.