Imagine hearing your wife whisper in your ear, telling you all the naughty things she did with a coworker in the backseat of your car. Instead of getting jealous, it turns you on. Maybe you enjoy the idea of how desirable your wife is. Or maybe you want to watch while she cheats on you, taunting you, forcing you to get involved in humiliating ways. Welcome to “cuckolding,” a taboo fetish that is far more common than you might think.

By definition, of course, a cuckold is the “husband of an adulteress.” The phenomenon itself is nothing new (see the works of Shakespeare or Chaucer). It might even be considered universal, since dozens of languages have a term that refers to it. Today’s cuckolding fetish, however, takes the deception and betrayal out of cheating—both partners are in on the secret.

While the average person may think the idea of sharing a spouse is horrific, the NASCA (North American Swing Club Association) estimates that at least 15 percent of married couples have opted for the swinger lifestyle. While swinging isn’t exactly cuckolding, the idea of willfully sharing a partner remains. According to Dr. Paul Abramson, a professor of psychology at UCLA and lead singer of Crying 4 Kafka, “Traditional American heterosexual relationships are built on monogamy. Cuckolding would thus be relationship suicide. But for relationships that have different boundaries, the impact might be trivial.” He says that if 50 percent of all marriages end in divorce, cuckolding can’t be the only thing to blame.

According to the General Social Survey conducted by the National Opinion Research Center, 19 percent of men and 14 percent of women admitted (key word: admitted) to having an extra-marital affair. Those statistics make sense considering the popularity of cheating websites like AshleyMadison.com that tout over 8 million members (that’s roughly about 2.5 percent of the U.S. population). Technology, of course, makes it easier to have a discreet affair.

Take Tinder, the newest hook-up craze. Download the app, find people within a certain radius, and swipe left or right based on whether you think the person is attractive. While the exact amount of booty calls generated by Tinder is impossible to pin down, Tinder founder and CEO Sean Rad told TechCrunch that the app witnesses 3.5 million matches along with 350 million swipes a day. And how many of those people are already in a relationship? Infidelity isn’t always the death of a relationship. For some, it seems to be a spark.

Some believe that cuckolding is really just exposed infidelity. In some ways, it spices up a sex life without the added guilt of cheating. While this fetish isn’t for the insecure, it’s certainly not for monogamists. (It’s definitely not for me.)

Isadora Almen, a licensed psychotherapist and board certified sexologist, says that the cuckold phenomenon cannot be explained any more than someone’s desire for bosomy blondes or being spanked. It’s an individual kink, one that she’s been answering questions about since the ‘80s. Almen says a man wouldn’t feel like he was a victim. Instead, he might think of himself as “particularly generous in seeing to his woman’s pleasure.” She adds a warning: “I wouldn’t recommend it as a sex therapist for spicing up one's love life. It could lead to jealousy and resentment. It’s pretty out there for most people and in many cases it’s the woman who is resentful and not the man whose kink it is.”

It’s not always about acting out a fantasy, sometimes it’s enough to just watch. Mean Cuckold is the highest selling DVD producer and director Glenn King has ever released. King says people are bored with regular sex. “Cuckolding is a way to humiliate a slave or explore sexuality," he says. "Infidelity is just performing the physical act of cheating on your spouse. You could say though, that infidelity is one way to cuckold a submissive.”

The act of cuckolding can often be filed under the female domination tab, as is evident in King’s series. There are three types of cuckolded men: the submissive, forced bisexual, and the voyeurs. “Submissives are into humiliation,” King says. “They fantasize about being degraded and humiliated by a beautiful woman. Second, you have guys who want to be pushed into exploring their darkest fantasies: forced bisexuality. They want to be pushed by their mistress into doing things they would never do, like worshipping another man. Then lastly, we have voyeurs, who just enjoy watching their lover get pleasured by another man. And to take it a step further, for those older males who grew up in the South, watching your woman have sex with a black man is absolutely shocking.”

If cuckolding is just another kink, like BDSM, why do so many shy away from ever mentioning it? Almen says it’s really all in the definition. “Cuckolding has always had with it the element of shame,” she says. “It really points the finger of shame at a man whose woman would go outside the relationship.”