Valentine’s Day has come and gone, so our thoughts turn from romance, flowers and candlelit dinners to … cheating? Though this may risk spoiling the holiday spirit, I’ve got to say it: A lot of people in relationships cheat. My in-depth interviews with 120 straight and gay undergraduate men in Britain and the United States, as well as broader research into monogamy, has shown that people are unfaithful more often than not. As we munch on leftover heart-shaped chocolate, let’s take another look at what we’ve wrongly assumed about fidelity.

1. Cheating and affairs are more common among the rich, and less common in conservative cultures.

From golf star Tiger Woods to Republican presidential contender Newt Gingrich, cheating seems commonplace among famous and wealthy men. But although studies find that the more money and celebrity men have, the more likely they are to cheat, cheating is hardly just the domain of the rich and famous. In fact, according to Boston College economist Donald Cox, poorer women are more likely to cheat than wealthy women.

Nor do more socially conservative times erase infidelity. America today may seem more sexually relaxed than the button-down years immediately following World War II, yet pioneering research by Alfred Kinsey found that married men cheated at rates of around 50 percent. In 1953, Kinsey showed that 26 percent of married women had also been unfaithful. Estimates today find married men cheating at rates anywhere between 25 percent and 72 percent. Given that many people are loathe to admit that they cheat, research on cheating may underestimate its prevalence. But it appears that cheating is as common as fidelity.

2. If you really love your partner, you’ll remain faithful.

Perhaps one of the most tragic misconceptions about cheating is that people stray because they have fallen out of love with their partners. We are taught to value fidelity as the litmus test of a relationship and conditioned to feel victimized if one cheats on us. But my research shows that young men don’t cheat because they have fallen out of love with their partners. Rather, they cheat simply because they desire sex with someone else, even if they want to preserve their relationship.

I found that, though 78 percent of the men I interviewed had cheated on their current partners, only a handful said they cheated because they were near the end of their emotional relationships. And women may respond to similar pressures: According to a 1999 study in the Journal of Social and Personal Relationships, 68 percent of female undergraduates also cheat.

3. We generally agree on what counts as cheating.

In Kinsey’s day, the meaning of cheating was simpler — it involved physical contact with another person. But today, the Internet and its democratization of pornography not only make yesterday’s stigmatized bedroom activities seem mundane but also force us to ask what defines cheating. A few erotic text messages? Former congressman Anthony Weiner’s lewd pics? What about a live Internet sex show, or “camming” — online sex via webcam?

I’ve found little agreement on what counts as cheating among today’s youth. “If you’re just in some chat room masturbating, and you are watching other people you’re chatting with, that’s not really cheating, is it?” one of my participants said. “You’re not actually doing anything with them. It’s just fantasy.”

Others disagreed. One said, “It doesn’t matter whether it’s just chat or camming, you’re cheating.” Unsure of what form of cybersex might upset a partner, the strategy of almost all of the men I interviewed, gay or straight, was don’t ask, don’t tell.

4. Your partner won’t stray if you keep your sex life exciting.

If you’re in a relationship, spicing up the physical intimacy won’t prevent cheating. Worse, buying into this myth makes the wronged individuals blame themselves for their partner’s infidelity.

For most people, monogamy does not necessarily provide a lifetime of sexual contentment. This is perhaps particularly true for youth who have grown up in a pornified culture; men in my study found themselves increasingly less interested in sex with their partners as months passed. Within two years, almost all of my subjects had cheated. “At the start I wasn’t cheating on her,” one explained. “But it felt like I was getting the same old thing. I just needed some other sex.”

5. Most married people don’t cheat.

In a 1991 study, sex researcher Shere Hite found that 70 percent of married women have cheated on their partners; a 1993 follow-up study found that 72 percent of married men have as well. According to a 2004 University of Chicago study, 25 percent of married men have had at least one extramarital affair. And with over 12 million members looking for extramarital intimacy on website AshleyMadison.com (tagline: “Life is short. Have an affair.”), it’s easier than ever to break marriage vows. A wedding ring is not insurance against cheating.

Although society cherishes monogamy, for most couples, the expectation of exclusive sexual activity is unsustainable. We may need to investigate other relationship models: open arrangements, or what sex columnist Dan Savage calls “monogamish” relationships in which couples have flings, affairs or threesomes. These ways of loving, along with polyamorous relationships and even singlehood, should be as equally culturally valued as monogamy. Only when men and women are able to make sexual choices free of stigma will people be honest with their partners about their desires.