Andrew Gotzis, a Manhattan psychiatrist with an extensive psychotherapy practice, has been treating a straight couple, whom we’ll call Jane and John, for several years. They have sex about three times a week, which might strike many as enviable, considering that John and Jane—who are in their 40s—have been together for nearly two decades. Based on numbers alone, one might wonder why they need couples counseling at all.

But only one of them is happy with the state of play. And it isn’t Jane.

“The problem is not that they are functionally unable to have sex, or to have orgasms. Or frequency. It’s that the sex they’re having isn’t what she wants,” Gotzis told me in a recent phone conversation. And like other straight women he sees, “she’s confused and demoralized by it. She thinks there’s something wrong with her.” John, meanwhile, feels criticized and inadequate. Mostly he can’t understand why, if his wife is having sex with him and having orgasms, she wants more. Or different.

Despite “fears of seeming sex addicted, unfaithful, or whorish” (Gotzis doesn’t like these terms, but they speak to his patient’s anxieties, he explained), Jane has tried to tell John, in therapy and outside of it, what she’s after. She wants to want John and be wanted by him in that can’t-get-enough-of-each-other-way experts call “limerence”—the initial period of a relationship when it’s all new and hot. Jane has bought lingerie and booked hotel stays. She has suggested more radical-seeming potential fixes, too, like opening up the marriage.

Read: The “untrue” woman

Jane’s perseverance might make her a lot of things: an idealist, a dreamer, a canny sexual strategist, even—again channeling typical anxieties—unrealistic, selfish, or entitled. But her sexual struggles in a long-term relationship, orgasms and frequency of sex notwithstanding, make her something else again: normal. Although most people in sexual partnerships end up facing the conundrum biologists call “habituation to a stimulus” over time, a growing body of research suggests that heterosexual women, in the aggregate, are likely to face this problem earlier in the relationship than men. And that disparity tends not to even out over time. In general, men can manage wanting what they already have, while women struggle with it.

Marta Meana of the University of Nevada at Las Vegas spelled it out simply in an interview with me at the annual Society for Sex Therapy and Research conference in 2017. “Long-term relationships are tough on desire, and particularly on female desire,” she said. I was startled by her assertion, which contradicted just about everything I’d internalized over the years about who and how women are sexually. Somehow I, along with nearly everyone else I knew, was stuck on the idea that women are in it for the cuddles as much as the orgasms, and—besides—actually require emotional connection and familiarity to thrive sexually, whereas men chafe against the strictures of monogamy.

But Meana discovered that “institutionalization of the relationship, overfamiliarity, and desexualization of roles” in a long-term heterosexual partnership mess with female passion especially—a conclusion that’s consistent with other recent studies.

“Moving In With Your Boyfriend Can Kill Your Sex Drive” was how Newsweek distilled a 2017 study of more than 11,500 British adults aged 16 to 74. It found that for “women only, lack of interest in sex was higher among those in a relationship of over one year in duration,” and that “women living with a partner were more likely to lack interest in sex than those in other relationship categories.” A 2012 study of 170 men and women aged 18 to 25 who were in relationships of up to nine years similarly found that women’s sexual desire, but not men’s, “was significantly and negatively predicted by relationship duration after controlling for age, relationship satisfaction, and sexual satisfaction.” Two oft-cited German longitudinal studies, published in 2002 and 2006, show female desire dropping dramatically over 90 months, while men’s holds relatively steady. (Tellingly, women who didn’t live with their partners were spared this amusement-park-ride-like drop—perhaps because they were making an end run around overfamiliarity.) And a Finnish seven-year study of more than 2,100 women, published in 2016, revealed that women’s sexual desire varied depending on relationship status: Those in the same relationship over the study period reported less desire, arousal, and satisfaction. Annika Gunst, one of the study’s co-authors, told me that she and her colleagues initially suspected this might be related to having kids. But when the researchers controlled for that variable, it turned out to have no impact.

Read: Multiple lovers, without jealousy

Many women want monogamy. It’s a cozy arrangement, and one our culture endorses, to put it mildly. But wanting monogamy isn’t the same as feeling desire in a long-term monogamous partnership. The psychiatrist and sexual-health practitioner Elisabeth Gordon told me that in her clinical experience, as in the data, women disproportionately present with lower sexual desire than their male partners of a year or more, and in the longer term as well. “The complaint has historically been attributed to a lower baseline libido for women, but that explanation conveniently ignores that women regularly start relationships equally as excited for sex.” Women in long-term, committed heterosexual partnerships might think they’ve “gone off” sex—but it’s more that they’ve gone off the same sex with the same person over and over.

What does it all mean for Jane and the other straight women who feel stultified by long-term exclusivity, in spite of having been taught that they were designed for it and are naturally inclined toward it? What are we to make of the possibility that women, far from anxious guardians of monogamy, might on the whole be more like its victims?

“When couples want to remain in a monogamous relationship, a key component of treatment … is to help couples add novelty,” Gordon advised. Tammy Nelson, a sex therapist and the author of The New Monogamy and When You’re the One Who Cheats, concurs: “Women are the primary consumers of sex-related technology and lubricants, massage oil, and lingerie, not men.”

Of course, as Jane’s example shows, lingerie might not do the trick. Nelson explains that if “their initial tries don’t work, [women] will many times shut down totally or turn outward to an affair or an online ‘friend,’ creating … a flirty texting or social-media relationship.” When I asked Gotzis where he thinks John and Jane are headed, he told me he is not sure that they will stay together. In an upending of the basic narrative about the roles that men and women play in a relationship, it would be Jane’s thirst for adventure and Jane’s struggles with exclusivity that tear them apart. Sure, women cheating is nothing new—it’s the stuff of Shakespeare and the blues. But refracted through data and anecdotal evidence, Jane seems less exceptional and more an Everywoman, and female sexual boredom could almost pass for the new beige.

Read: Why are young people having so little sex?

It’s not uncommon for women to let their straight partners play in a “monogamy gray zone,” to give guys access to tensional outlets that allow them to cheat without really cheating. “Happy ending” massages, oral sex at bachelor parties, lap dances, escorts at conferences … influenced by ubiquitous pop-cultural cues, many people believe that men need these opportunities for recreational “sorta sex” because “it’s how men are.” It’s how women are, too, it seems.

Women cannot be pigeonholed; the glory of human sexuality is its variation and flexibility. So when we speak of desire in the future, we should acknowledge that the fairer sex thirsts for the frisson of an encounter with someone or something new as much as, if not more, than men do—and that they could benefit from a gray-zone hall pass, too.