What Is Sexual Fluidity, Really?

"My guy pretty like a girl. And he got fight stories to tell," Frank Ocean sings on his new single. "I see both sides like Chanel."

Ocean is one of a growing number people—albeit, probably the one with the highest profile—who in recent years have begun to publicly resist strict labels on their sexuality. It could also explain why, especially among students in my human sexuality classes, one of the most frequent questions I get is on the topic of sexual fluidity. Thanks in part to celebrities like Ocean—not to mention Miley Cyrus , who identifies as pansexual, and Kristen Stewart, who has said that she's bisexual but also declared herself "so gay " on a recent Saturday Night Live episode, sexual fluidity is having a moment.

And what I've found is that people are intrigued, but also confused. So, what exactly does it mean to be sexually fluid? Let's start with the basics: The term first gained widespread popularity after the publication of a 2008 book, Sexual Fluidity: Understanding Women's Love and Desire , by the researcher Lisa Diamond, a psychologist at the University of Utah.

In short, sexual fluidity refers to the idea that a person's attractions, and therefore their sexual identity—lesbian, gay, bisexual, heterosexual—can change over time. That's not a new idea: More than 70 years ago, sex researcher Alfred Kinsey and his team noticed this possibility when they interviewed thousands of Americans about their sexual lives and experiences. It wasn't unusual for people to describe sexual attractions to or even sexual behaviors with members of both sexes. There are at least two beautifully written and acted scenes depicting this in the film Kinsey that come to mind, which you should watch if you haven't yet. (Full disclosure: I work with the Kinsey Institute, which continues to research human sexuality.)

To describe this "shifting" in scientific terms, Kinsey and his colleagues created what they called the Heterosexual-Homosexual Rating Scale—commonly known as "the Kinsey Scale." On one end of the scale, a rating of zero means "exclusively heterosexual" and on the far end a six refers to being "exclusively homosexual." Yet in their research, they noted that many people's sexual behavior was somewhere in between, and there could actually be movement along the scale over the course of a person's lifetime.

That idea is clicking with a lot of people today: For instance, maybe a woman was always into men and identified as heterosexual. Then she developed a particularly close emotional bond with another woman (emotional attachments are a common pathway to sexual fluidity, though certainly not the only way), and found herself sexually attracted.

Sometimes, women who go through this experience still consider themselves heterosexual, but into women. That's where it can get confusing: Their attraction shifts, but they still identify with the same orientation. Other women come to identify as bisexual or lesbian, both in identity and attraction. All of this underscores how personal and subjective, ultimately, a person's sexual identity is. Put simply, you get to come up with your own identity and describe it as you see fit.

That's something I remind my students when they describe their interests or behaviors and ask me to tell them "what they are." That's not for me to decide: As a researcher, I often have participants describing their identity as everything from "open" to "it's the person, not the gender" to "bicurious" and "it depends."

Obviously, these gray areas can be hard to accept if you're someone who believes we're all born with a single, persistent sexual orientation. Decades worth of research, however, suggests that's just not the case: Sexual orientation is in fact highly complex, and there are likely multiple influences on who you're attracted to and who you have sex with—including medications your mother may have taken while pregnant and even, if you're a guy, your birth order.

Most of the research to date, however, has focused more on women than men. So far, it seems that more women than men report changes in their sexual attractions and identities—particularly women who are sexual minorities, like lesbian and bisexual women. Bisexual men, as you might expect, also report higher than average levels of fluidity. And as I mentioned before, it's not unusual for some hetero-identified people to describe having had some kind of intimate same-sex experience. Even people who identify as asexual have experienced these shifts.

So why should all this matter to you? For one thing, if you find yourself attracted to a gender you were never into before, it's important to know that those feelings aren't rare or weird or abnormal. And if a friend or family member or partner shifts, understanding this basic fact may help you to be more compassionate and accepting—especially when other people might not be as understanding.

Love and sexual attraction are complex. Sometimes things make perfect sense and it's easy to rationalize why we've fallen for someone. Other times, however, I'm hard pressed to put it any better than the French writer Michel de Montaigne. "If pressed to say why I loved him," de Montaigne once wrote, "I can only say because it was him, because it was me."

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