At one time or another, everyone has discovered that being told not to do something only serves to make us want to do it even more. It is a basic part of human nature to feel a magnetic attraction toward the taboo. As someone who studies sex and relationships for a living, I see this all of the time in my work: people are attracted to whom and what they are told they can’t have.

This pattern of behavior occurs so often that sex therapist Jack Morin gave it a formal name: the erotic equation. He describes it as a mathematical formula of sorts:

Attraction + Obstacles = Excitement

The basic idea is that if a person experiences even a slight attraction to someone or something, any obstacles to acting on that attraction will only enhance its appeal.

This equation is of particular relevance to my research because it helps to explain where a lot of human sexual fantasies and desires come from. We have all been told there are certain things we cannot or should not do when it comes to sex (such as mixing pleasure with pain or playing with power), but instead of abiding by these social prescriptions, we tend to eroticize them in a major way.

As those who have read my book Tell Me What You Want (2018) are aware, I spent two years conducting the largest and most comprehensive survey of sexual fantasies ever undertaken in the United States. This survey formed the basis for my book and involved 4,175 Americans from all 50 states. I tried to collect as diverse of a sample as possible in terms of sexual orientation and gender, political and religious background, race, and age in order to look at what people from all walks of life fantasize about.

When I analyzed the content of people’s favorite sex fantasies of all time, I found that for people of all backgrounds, sexual taboos were extraordinarily common. Not only were taboo elements present in most people’s favorite sex fantasies, but nearly everyone said they had fantasized about doing something taboo at least once before.

The most popular taboo of all was BDSM: bondage, discipline, dominance, submission, sadism, and masochism. Basically, what we are talking about here are activities that involve themes of power, control, and rough sex—think things like pegging, nipple torture, or being “forced” to have sex. BDSM has long been viewed as a taboo act in the United States, in part, because American psychologists and psychiatrists historically classified sadomasochism as a mental disorder. The cultural narrative around BDSM is that this is an unhealthy and dangerous activity. To engage in it—or to even express interest in it—is to violate a big taboo.

BDSM is not a universal taboo, of course. The entire concept of a sexual “taboo” is inherently arbitrary because what is considered taboo in one time, context, or culture may be considered perfectly normal in another. As a result, the taboo allure of BDSM is something that varies across social groups, which is a fact I saw play out in my data.

Through my study I discovered that BDSM is more of a taboo for some Americans than it is for others. One example is the differences I found between political parties. It is well known that in Democratic circles, having a “level playing field” and promoting equality are popular values, whereas power differentials—especially in sexual contexts—are taboo. It is for this reason that many Democrats support policies that ban relationships between superiors and subordinates in both the workplace and in academia, with some going so far as to suggest that such relationships can never be consensual because they involve a power differential.

So, what did I find when I looked at Democrats’ sexual fantasies? I found that Democrats reported more fantasies featuring BDSM, including forced sex, than did Republicans, for whom power play is not quite so taboo.

This difference makes sense when taking into consideration that Republicans tend to endorse more traditional gender roles, and those roles have an inherent power differential. Compared to Democrats, Republicans tend to face stronger moral prohibitions against things like non-monogamy and same-sex attraction, which means that fantasizing about sex with more than one partner or having “gay sex” would be taboo.

Guess what I found when I looked at Republicans’ sex fantasies? Compared to Democrats, Republicans reported more fantasies about all kinds of non-monogamy, including infidelity, swinging, orgies, and cuckolding (a practice that involves watching your partner have sex with someone else). Also, among men who said they were exclusively heterosexual, more reported same-sex fantasies to the extent that they described themselves as Republican rather than as Democrat.

In other words, we seem to be drawn to whatever is considered taboo for us based on the social groups to which we belong.

So, what is up with this erotic equation? Why are Democrats drawn to BDSM and forced sex, while Republicans are drawn to non-monogamy? Why do human beings want what we are told we are not “supposed” to want in the first place?

The answer to these questions can be explained by a psychological principle known as reactance. The basic idea is that when our choices are limited or we perceive a threat to our freedom to behave how we want to it creates a state of unpleasant arousal because we feel as though we have lost something. When faced with unpleasant arousal, we seek to resolve it. In this case, we have a tendency to do so by asserting our freedom to act—or rather, to have sex—as we please. In other words, we react to restrictions by reestablishing our freedom to choose our own destiny.

This means that if you find yourself turned on by something that might be considered taboo—like forced sex—you are not alone, despite the fact that you may think this makes you a “deviant” person. I see in my research on sex fantasies that the more rare and taboo people think their fantasies are, the more shame, guilt, and embarrassment they feel about them. The more of this anxiety that people feel about their sexual turn-ons, the less likely they are to communicate their sexual wants and needs with their partners and the more likely they are to be dissatisfied with their sex lives and relationships.

What we need to do, then, is to help everyone understand that having taboo sex fantasies and desires—whether they are about BDSM, non-monogamy, fetishes, or something else—does not make them a “pervert,” nor does it make them a bad person. The truth is that if you are turned on by taboos, you are actually pretty normal and maybe not quite as kinky as you think. Because it turns out that to want what you are told you can’t do or shouldn’t have is simply to be human.