People like to say that American culture has a puritanical streak: one that entails, among other things, a certain haughty piousness, instilled by the killjoys who reached New England’s shores in the 17th century. Yet the Pew Research Center, in a pair of reports released last month, asked participants in various countries about a host of moral issues—and found few in the United States that were widely condemned. Spanking children? Doctor-assisted euthanasia? Clear majorities said they weren’t morally wrong. Gambling? Marijuana use? Compared with respondents in many nations, Americans were notably permissive. The poll also revealed clear political divides: Republicans were much more likely to oppose homosexuality and divorce, for instance, and Democrats were more likely to reject the death penalty and extreme wealth.Only one behavior, in fact, received near-unanimous disapproval: infidelity. Ninety percent of Americans said that a married person having an affair is morally wrong, and their position didn’t differ dramatically based on political party, age, or gender. Compare that to Germany and France, where participants were roughly split down the middle.The Pew poll is one of many suggesting that when it comes to monogamous commitment, Americans aren’t messing around. Well—technically they are: Studies indicate that a third to half of people in the U.S. have been sexually unfaithful, according to the evolutionary biologist Justin Garcia’s new book, The Intimate Animal. If you were to include “emotional infidelity” or kissing, which apparently some people don’t think is cheating, the numbers would rise. But that hasn’t stopped Americans from judging cheaters, even as attitudes toward other sexual behavior—premarital sex, casual sex, the use of contraception—have loosened.[Read: The basic drive that humans might be losing]No one wants to be deceived. Yet disdain for cheating seems to derive less from a simple desire for honesty and more from a commitment to the couple as an exclusive unit. Consensual nonmonogamy is widely stigmatized; one 2021 study found that of participants who weren’t personally interested in engaging in polyamory—meaning multiple romantic relationships—only 14 percent said that they respect people who do practice it. And of course, there are many ways to betray a partner that have nothing to do with sex—and that many people seem more willing to forgive. For a qualitative study, Jenny van Hooff, a sociologist at Manchester Metropolitan University, interviewed a woman whose partner had racked up a massive amount of debt without her knowledge; collectors came and stripped the house of her belongings, and she herself had to pay back what was owed. “But it’s so much better,” she told van Hooff, “than if he cheated on me.”Monogamy, it seems, is one of the few moral rules that Americans feel they can grasp onto, in an age when many no longer look to religion or a unified culture for social norms. It serves many people well: Committing to one partner, growing together through change, and staying loyal even when it’s difficult can grant them profound purpose. Yet other sources of meaning and community exist, too—and other ethical obligations. The intensity of the American allegiance to monogamy might reveal something about national priorities: a sense of duty to ourselves, our partners, and our household—perhaps more than to anything or anyone outside of it.Amy C. Moors, a psychologist at Chapman University, likes to play a game with her students. She tells them that in the United States, people who get married can receive a certain number of federal benefits. She names some examples: joint income-tax filing, medical decision-making authority, the ability to sponsor someone for immigration. Then she asks how many laws they reckon consider marital status in determining who’s eligible. No one has ever guessed more than 100.The answer is more than 1,000. Some of these laws are enormously consequential: They could grant someone housing assistance, or custodial rights, or bereavement leave after a partner dies. Others are niche: One concerns who can inherit land on Lake Michigan’s Sleeping Dunes National Lakeshore, now that it has become a national park. But Moors’s point is that compared with other countries, the U.S. offers an especially robust package of spousal perks.Americans are motivated to think of marriage, in other words, as the key to a stable and virtuous life. Fewer have actually been getting hitched, but that might be a testament to how seriously the institution is taken; people tend now to think of matrimony as something for which they need to prepare—save up money, get their career in order, find their soulmate. And monogamy is commonly associated with all kinds of positive traits: It receives what psychologists call a “halo effect.” In one study, when Moors and her colleagues described fictional characters as monogamously coupled, participants were more likely to see those characters not only as good partners but as good people—ones who recycle and tip generously and walk their dog regularly.[Read: The slow, quiet demise of American romance]Van Hooff thinks that esteem is actually part of why infidelity is so despised: The more that you depend on monogamous partnership, the more terrified you are of losing it. She’s based in the United Kingdom, but she sees a lot of similarities between her country and the United States—both are societies, she told me, where many people get the bulk of their support from a partner or nuclear family, rather than from broader networks of, say, friends or congregants or extended kin. Americans especially, van Hooff said, tend to value self-improvement as a kind of ongoing project, and a relationship can be one way to feel they’re accomplishing what they’re meant to. Any threats to that source of security and identity can feel catastrophic. And the average couple today spends a great deal of time together—more than those in generations past, according to one analysis. When partners are so deeply enmeshed in each other’s lives, the idea that one might not always know what the other is doing, or what they desire, can be disturbing. The monogamous ideal sits on a pedestal so tall that it’s wobbling like a Jenga tower.The irony, van Hooff believes, is that the same individualistic tendencies that might make cheating such a frightening prospect may also make it tempting. “We’re encouraged to maximize personal fulfillment, which means that the self-sacrifice involved in not having affairs,” she said, “is harder to sustain.”Other factors, too, have paved the way for adultery. FDA approval of Viagra, in 1998, marked a rise in older men cheating. New technologies have made beginning and carrying out affairs easier, though they have also made it easier to get caught. (One woman van Hooff interviewed discovered her husband’s infidelity when he was out and a string of messages popped up on his iPad; by the time he came home, she was waiting with the evidence printed out.) And people are living longer now. Promising to be faithful forever is a more ambitious claim.You might think that in 2026, a clear solution to the cheating problem exists: People should just be open about their interest in sleeping with or dating other people. “Ethical” or “consensual” nonmonogamy is a more visible option than it once was. But van Hooff’s interview subjects haven’t viewed this as a clean fix. Some of them, even when faithfulness feels hard, simply don’t want to open their relationship. Others are scared to cause friction by mentioning the possibility.They’re not wrong to be scared. Psychologists have found that consensual nonmonogamy has a negative “halo effect”: In one study, characters described as nonmonogamous were judged less caring, less reasonable, and less likely to floss. Carrie Jenkins, a philosopher studying romance at the University of British Columbia, has written about nonmonogamy and practices it herself—and she regularly gets hate mail. That she would take interest in this subject might seem logical; thinking about the nature of love is literally her job. She never suggests that monogamy is inferior to other relationship structures, merely that it’s not the only one. Yet her work seems to make people powerfully, emotionally defensive.Jenkins suspects that monogamy is simply so integral to American identity that any alternatives are “received as an attack” on the collective—rather like rooting against your home team. Although she’s British and lives and works in Canada, she has noticed that much of her hate mail refers to “American values.” One correspondent, inviting Jenkins to choke herself, added, “God bless America” and a quick ode to “Freedom” and “second Amendment rights.”[Read: Why marriage survives]Yet nonmonogamy, like infidelity, is quietly common at the same time that it’s publicly unpopular. In its 2024 Singles in America survey, conducted with the dating company Match, the Kinsey Institute found that nearly a third of participants had at some point been in a consensually nonmonogamous relationship—including polyamory, open relationships, or swinging (not casual dating). Moors—the Chapman University psychologist, who’s also a research fellow at Kinsey—likes to point out that this is similar to the share of Americans who have a pet cat, and greater than the share who are left-handed or speak a language other than English at home. And though consensual nonmonogamy has frequently been described in the press as an elite fad, research doesn’t back up that idea. One 2018 study found that participants in polyamorous relationships were more likely than those in monogamous ones to make less than $40,000 a year. In both 2016 and 2021, the Kinsey Institute found no association between polyamory and any religion, race, political affiliation, geographic location, or income category. “Polyamorists,” a press release states, “were as likely to be Republican or Democrat, poor or wealthy, white or Black, on the coasts or in the middle of the country.”If nonmonogamy seems to come up largely in the context of Brooklyn moms or Portland kombucha brewers, that’s likely because these are the ones who feel at ease talking about it openly. Moors has spoken with many people who just carry on making private agreements with their partners, selectively telling people close to them. They’re not cheating, but they still have to live with secrecy—and maybe some shame: Ethical nonmonogamists themselves have been shown to rate monogamous subjects more favorably than nonmonogamous ones.So an odd kind of paradox has arisen. Nonmonogamy has gained real attention; a growing number of people are practicing some form of it. Yet instead of becoming normalized, the practice has mainly triggered a whole lot of pushback. Over the 15 years that Jenkins has been studying polyamory, she told me, cultural attitudes have been “quite regressive.” Even in progressive circles, which might profess to be more welcoming to some groups on the margins, the argument is often that nonmonogamy is bad for feminism, that it’s essentially a way for men to justify cheating. (See recent debates about Lindy West and Lily Allen.) The idea that consensual nonmonogamy is generally harmful for women isn’t particularly well supported by research, but it might allow people who identify as open-minded to feel that their discomfort with nonmonogamy is rational, even just. Another message that Jenkins gets from strangers is the kind that professes concern over her best interest—warning her to be monogamous for her own good.What a tortured relationship Americans have with monogamy. They can’t live with it; they can’t live without it. Pundits who panic about monogamy’s demise aren’t necessarily wrong. Only a minority of Americans live up to the nuclear-family model: two married parents with kids, all under one roof, their relationship not open or adulterous. Maybe people are so protective of monogamy because they can sense that it really is vulnerable. The problem is that they end up putting immense pressure on the custom to provide them with purpose and complete fulfillment. It’s perhaps no wonder that so many people cheat; they may want more from their relationship than it can ever really give them. The glass gripped too tightly will shatter.None of this is to say that we should celebrate affairs. But I do believe that all of the self-appointed moral umpires could “take the temperature down,” as van Hooff put it. So many people are taught to tremble at the idea of infidelity. And it can be absolutely devastating, of course—not only for the partner who’s cheated on but also potentially for kids who pick up on what’s happening. But relationships survive infidelity all the time. Just like a million other mistakes, she said, it’s a “normal human failing.”Van Hooff has found that cheating usually has less to do with unhappy relationships and more to do, frankly, with mortality. Extramarital affairs are less common among young adults than among people in their 50s and up, who might have been in the same job, seeing the same friends, carrying out the same routines for decades—but who don’t want to stop growing or to run out of time for new experiences. She has a lot of empathy for the adulterers she’s interviewed, who tend to feel horrible about their betrayal but exhilarated by the idea of trying on an alternate future—especially in a society that doesn’t always grant older people new opportunities, or make them feel seen at all.[Read: The existential terror of monogamy]As for ethically nonmonogamous partnerships, psychologists have found that they’re about equal to monogamous ones in terms of relationship satisfaction, commitment, and sexual satisfaction. “If you like monogamy, go and do that,” Moors summarized. “And if you like consensual nonmonogamy, go do that.”I found the Pew results a little tragic—not because monogamy is a bad thing to go to bat for, but because we have limits on our moral energy and attention. What does it say that participants were collectively most critical of cheating, the consequences of which are usually limited to an individual or a family, and least critical of eating meat? I’m not a vegetarian, so I’m not judging from on high, but I was struck by the fact that 96 percent of respondents said the latter is morally acceptable.So many people seem to be yearning for belonging and direction, and they’re searching for it in partnership, in the nuclear family, in the monogamous ideal that connects diverse Americans at one fragile point of unison. But that very priority might be distracting them from any broader sense of connection—from feeling, finally, like they’re part of something bigger.When you buy a book using a link on this page, we receive a commission. Thank you for supporting The Atlantic.