Everyone has a sexual fantasy—a specific type of sex or a certain place or position that excites you whenever you think about it. But for most of us, our favorite fantasy is a closely guarded secret. We worry that it's too edgy or weird, and we'll be judged for it. Or there's an element of danger that makes it too risky.

One sex researcher is making the case that your go-to sexual fantasy probably isn't as unusual as you think. That's what we learned from the upcoming book Tell Me What You Want: The Science of Sexual Desire and How It Can Help You Improve Your Sex Life by Justin Lehmiller, PhD. After conducting a survey, Lehmiller identified seven fantasy themes that rank as the most popular among Americans. The top three on his list are fantasies that just about everyone has had at one time or another.

Here, he breaks down each one, telling Heath about the psychology behind the fantasy, why it's completely normal, and how you can approach your partner and make it happen IRL.

Group sex

This popular fantasy includes everything from a menage a trois to a multi-person orgy, and it can include men, women, and both. Why is it so common? Even though you might love and feel close to your partner, monogamy can get, well, dull.

“It’s human nature to grow bored with sexual routines—and it’s easy to fall into a routine when you have just one partner for a very long period of time,” Lehmiller says. “Group sex provides an opportunity to spice things up.” If you find yourself fantasizing about group sex often, he suggests this could signal that your real-life sex life has become predictable. Other reasons could be that you’re a “sensation seeker” or extravert.

Rough sex

Glued to the TV whenever 50 Shades of Grey is on? You're not alone. Millions of people fantasize about participating in rough action, such as S&M (sadism and masochism) or BDSM (bondage, discipline, submission, and sadomasochism).

“BDSM is a popular sexual desire in part because participating in it changes your state of mind,” Lehmiller says. “People who take on submissive roles experience an escape from self-awareness, while those who take on dominant roles experience enhanced focus. In both cases, these psychological changes make you less likely to be distracted and, therefore, more likely to let go and enjoy the experience.”

What kind of person fantasizes about sex as an expression of power? Lehmiller says you could be seeking out something different, or that you find yourself distracted during sex. It could also be one way some people learn to cope with sexual anxiety.

Thrill-seeking, adventurous sex

Turns out boredom is behind this sexual fantasy as well. “Thrill-seeking activities are largely popular for the same reason as group sex: They help to fend off boredom in the bedroom,” Lehmiller says. “Having sex in new locations and trying new positions or activities has the potential to amp up our arousal and give us those feelings of excitement that we crave.”

Sex on a beach, anal sex, joining the mile high club, and bringing food into the bedroom are other examples of fantasies that are all about increasing novelty and excitement. If it's your favorite fantasy theme, it could signal that you’re looking for a break from your routine sex life, or that you’re trying to find some sort of escape, he says.

Fetishes and taboo sex acts

“A big part of the reason taboo activities are appealing is because we come to want what we’re told we can’t have,” Lehmiller says. “This is a basic principle of psychology called reactance, and it applies to both sexual and non-sexual things. If you tell people not do something, no matter what it is, this is going to make some people want to do it.”

Taboos or fetishes—think being a peeping Tom or finding sexual gratification in an object, like shoes or nylon stockings—might also be tempting if you’re part of a social group that has strict rules about appropriate sexual behavior, Lehmiller says.

Non-monogamous sex

Open relationships and polyamory are increasingly acceptable lifestyle choices for lots of couples—and they're sexual fantasies for many people who are in traditional monogamous relationships. Desiring a non-monogamous relationship "is not just about meeting sexual needs, but fulfilling various emotional and intimate needs, too,” Lehmiller says. “Nonmonogamy is appealing to many people because it’s hard for one partner to be everything to us in all ways.”

Lehmiller says that a person who has non-monogamy fantasies might be someone whose sexual or romantic needs aren’t being met. On the other hand, it could also suggest that you’re more extroverted, or you don’t tend to get jealous.

Passionate, romantic sex

This fantasy theme is about the trappings of seduction: candlelit dinners, mind and body intimacy, and a partner who deeply desires you. “Feeling wanted and connected to other people is a basic human need,” he says. “Our sexual relationships have the potential to fulfill this need by demonstrating in clear and unambiguous terms that we are desired." Having a partner who is intensely passionate about you, adds Lehmiller, is a great way of validating our need for social belonging and intimacy.

If you find yourself fantasizing about sexual passion, it’s possible that you don’t feel desired enough in real life. Lehmiller says that people who do not feel good about themselves or their relationships are more likely to fantasize about adding passion to their lives.

Homoerotic sex and gender-bending

Fantasies involving someone of the same gender can be very surprising for some people, and it may make them question their own sexual orientation. But while issues with sexual orientation might be driving the fantasy, Lehmiller believes it's more a response to a ho-hum sex life.

“Testing the boundaries of your gender and sexual orientation can be sexually appealing for a few reasons,” he says. “Obviously, one is introducing some novelty or excitement. However, another is breaking a taboo—doing something that you’re not ‘supposed’ to do.” Curiosity about trying something different or escaping society pressure to conform are potential factors, he says.

How to indulge your fantasy IRL

Having a conversation with your partner about the fantasy scenario raging in your head can be challenging and nerve-wracking. Understandably, you're worried about being laughed out or considered freaky. And that rejection on the part of your significant other can have deep emotional repercussions.

Lehmiller suggests going about it like this. “Consider sharing your ‘vanilla’ fantasies first—the ones that you think your partner would be most likely to be on board with,” he says. “Building up trust and comfort with each other can help lay the groundwork for sharing—and maybe even exploring—more adventurous desires later on.”

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Lehmiller also says it’s important to be comfortable with your fantasies before you can communicate it to your partner and act on it.

“A lot of times, people don’t share their fantasies because of their own personal feelings of guilt, anxiety, or embarrassment,” he says. “In cases like this, you need to figure out how to come to terms with your desires. Professional counseling might be warranted in some cases because tackling shame can be a tough thing to do on your own.”