When word spread that cheating website Ashley Madison was one big sausage fest, with some sources claiming that up to 95 percent of its users were male, no one was that surprised. Conventional wisdom says that women are hard-wired for monogamy; that guys are the ones who can’t keep it in their pants.

But here’s a little secret: Women are every bit as likely to stray as men are.

In a recent study from Indiana University, about 20 percent of both men and women copped to having cheated on their current partners. Other research confirms that the two-timing stats are even between the genders.

One of the researchers behind the Indiana study, Kristen Mark, Ph.D., says this is a big shift: Male philanderers used to outnumber women. But it’s unclear whether more women are cheating now, or if they’re just more willing to admit it to researchers.

You can blame infidelity on evolution, but in 2015, it’s about more than trying to propagate the human race.

People get bored and curious, according to Mark’s research. No matter how much you love your partner, sex for the 752nd time with him or her probably won’t seem as exciting as illicit first-time sex with a stranger at the bar. You get tempted, and without adequate self-restraint—or with adequate doses of Jack Daniel’s—you falter.

Still, men and women tend to cheat in different ways—which may explain why the Ashley Madison user base is allegedly all male, says Paul Hokemeyer, Ph.D., a licensed marriage and family therapist based in Los Angeles and Telluride.

The site caters to what many guys want: Sex with no strings attached, says Hokemeyer.

Many women, on the other hand, tend to look for an emotional connection to accompany sex—even if it is extramarital, he says. They crave the boost in oxytocin, the feel-good hormone, they get from connecting with someone else.

For this reason, female infidelity may often be less premeditated than, say, signing up for an affair website to find a sex partner, says Mark. Women may be more apt to meet someone first—for example, at work or out at a bar—feel sparks, form a relationship, and then cheat.

The downside: While men tend to compartmentalise their affairs—“it’s just sex”—women sometimes become more wrapped up in them, says Hokemeyer.

“Women are invested in outcomes and value the process of connection,” he says. “They feel the intensity of the affair, rather than thinking of it as inconsequential or without meaning and impact.”

The good news is that the strength of your relationship plays a major role: Women in happy unions are far less likely to cheat, according to Mark’s research.

(To affair-proof your relationship, just make sure you stay connected, says Hokemeyer. Don’t let small squabbles snowball, and don’t let any anger or resentment build up.

“It may be the last thing you feel like doing, but attending to the small breaches will prevent you from having to close the huge abyss that results from infidelity down the road,” he says.