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Many men and women who identify as heterosexual—and may well be married—have about same- sex. Some even engage in periodic same-sex play, and wonder if they’re really gay/lesbian. A good deal of hetero-focused features “girl-girl” scenes. And many people who identify as gay/lesbian have had heterosexual experiences.

That’s bisexuality, “swinging both ways,” or being “AC/DC.”

But bisexuality has long been a controversial concept for many. Some authorities have argued that it doesn’t exist—that people are straight, homosexual, or . Others have dismissed bisexuality as youthful experimentation along the road to embracing one’s “real” .

However, the weight of the research shows that bisexuality is real—not a passing fancy but quite often a lifelong orientation. Just as some heterosexuals still believe (incorrectly) that homosexuality is “abnormal,” some heterosexuals and homosexuals feel the same way about bisexuality (also incorrectly).

Does Bisexuality Exist?

Researchers first described bisexuality during the 19th century. Their observations culminated in the early 1950s when Alfred Kinsey of the University of Indiana, America’s first scientific sex researcher, argued in favor of a “sexual continuum.” Kinsey’s huge survey of Americans’ showed that most people are exclusively heterosexual or homosexual, but that some fall in between in various degrees of bisexuality. (Kinsey himself was bisexual—married and mostly heterosexual, but with some homosexual interest and many gay experiences.)

But as soon as scientists first described bisexuality, other investigators insisted that it didn’t exist. Their dismissals rested on three arguments:

Bisexuals were heterosexuals who were “just experimenting.”

Bisexuals were people confined in single-gender institutions (prisons, monasteries) who reluctantly made do with the only available gender.

Bisexuals were homosexuals who did not want to be stigmatized as such, and so they feigned to the opposite sex.

These dismissals are still with us today. College women involved with other women are sometimes called LUGs, or "Lesbians Until Graduation"—when, presumably, their youthful experimentation ends and they revert to their “real” (and straight) orientation. Meanwhile, some lesbians and gays view bisexuality as a cowardly refuge for homosexuals who lack the courage to come out.

As many heterosexuals began celebrating sex for pleasure (as distinct from procreation) during the so-called Sexual Revolution of the 1960s and 1970s, homosexuals began celebrating their own sexuality—and fighting prejudice and against them. Around the same time, bisexuality emerged in the media spotlight. A 1974 Newsweek article was titled “Bisexual Chic: Anyone Goes.” Around that time, the first bisexual organizations formed—in Boston, a bisexual discussion group, the Bivocals; and out west, the San Francisco Bisexual Center, which published a newsletter, the BiMonthly. Still, however, research into bisexuality remained scant. The Journal of Bisexuality did not begin publishing until 2001, and books about homosexuality outnumber books on bisexuality by at least 100 to one.

Ironically, as bisexuality gained more media notice, some homosexuals stepped up their attacks, calling it a “cop-out” or a “betrayal” of bisexuals’ presumed “true nature” as homosexuals.

Starting in 1981, AIDS transformed our understanding of bisexuality, as a surprising number of ostensibly heterosexual, often married men began turning up with the disease. It soon became apparent that sexual identification was often distinct from sexual behavior. Men could identify as hetero and live hetero lives, yet have periodic, even regular, homosexual experiences—not just experimentally, but over the long term.

However, in a 2005 study that made headlines, Northwestern University researchers declared that bisexuality did not exist. They asked 101 young men—30 of who identified as straight, 38 as gay, and 33 as bisexual—to watch erotic videos with their genitals wired to detect arousal. The straight men were aroused only by heterosexual videos and the gays only by homosexual action. Among the men who identified as bisexual, three-quarters were aroused by the gay videos and one-quarter by the straight porn, with none aroused by both. The researchers’ conclusion: straight, gay, or lying.

Bisexual groups savaged the study because the researchers had recruited participants by in gay periodicals, possibly skewing the results. Six years later, the researchers repeated their study, this time recruiting through online sites catering to bisexuals. They found that, in fact, most self-identified bisexuals became aroused by both straight and gay erotic videos.

Prevalence?

From 2006 to 2008, the Centers for Disease Control and Prevention’s National Survey of Family Growth surveyed Americans on their sexual orientation, and found that 16% of women and 5% of men declined to select straight or gay, insisting that they were somewhere in the middle, attracted to both genders to varying degrees.

Age-Related

In Kinsey’s studies, about 4% of women and 10% of men admitted having had sex with both men and women, but only 2% of women and 5% of men claimed to be truly bisexual. This suggests that some bisexuality may actually be youthful experimentation—but not all.

A study by Morton Hunt for Playboy in the mid-1970s found that about 15% of post-pubertal men, and 10% of women, had had sex with both genders. But Hunt and other researchers found that considerably lower proportions maintained a lifelong as bisexual—just 3% of women and 5% of men. (For comparison, depending on the study, 5% to 10% of the adult population identifies as homosexual.)

In 2015, in surveys of American and English adults, the market research firm YouGov stratified sexual orientation by age group and found that bisexuality is more prevalent among the young than the old:

Completely heterosexual or homosexual:

Age 18-29: 66%

Age 30-44: 75%

Age 45-64: 90%

Age 65+: 93%

Varying degrees of bisexuality:

Age 18-29: 29%

Age 30-44: 24%

Age 45-64: 8%

Age 65+: 7%

Why do fewer people identify as bisexual as they age? It’s unclear, but presumably, social pressure pushes at least some bisexuals to choose either straight or gay.

Prejudice Against Bisexuals

In the U.S., homophobia has become increasingly culturally unacceptable, yet “biphobia” is alive and well. A 2013 University of Pittsburgh study showed that many straight and gay people reacted negatively to bisexuality with 15% of straight men insisting that bisexuality doesn’t exist. Compared with heterosexuals, lesbians and gay men were less prejudiced against bisexuality, but still, many showed little sympathy for swinging both ways.

A study of college students’ attitudes in the mid-1990s asked participants if they considered homosexuality acceptable or unacceptable: 43% said male homosexuality was unacceptable, while 38% said the same about lesbianism. Significantly larger proportions, however, disapproved of bisexual men and women—61% and 50%, respectively.

Other studies have shown that, compared with impressions of gay men and lesbians, more people believe that bisexuals are promiscuous, unfaithful to their lovers, unable to make a long-term commitment to a single person, and more likely to infect a lover with a sexually transmitted infection.

Many homosexuals continue to believe that bisexuality is a “phase” in the process of coming out. In one study, 80% of lesbians felt that way about bisexual women.

The Real Lives of Bisexuals

One myth about bisexuals is that they are involved with both men and women simultaneously. Available studies suggest that only a minority of bisexuals maintain simultaneous relationships with both genders. They are more likely to switch back and forth. In one report, self-identified bisexuals were asked if they had been sexually involved with both men and women during the past 12 months. About two-thirds said yes (66% of the men, 70% of women). However, only about one-third said they’d ever been simultaneously involved with both genders.

Another myth is that bisexuals are more promiscuous than straights or gay/lesbians. The research is scant, but one study of 105 bisexual men, aged 19-62, found a lifetime average of 23 male sex partners and 23 female. This suggests that bisexual men have more lovers than the typical heterosexual, but fewer than many gay men. (There have been no studies of women bisexuals’ numbers of lifetime partners.)

It’s Not Easy Being Bisexual

Bisexuals talk about “coming out twice"—once as gay or lesbian in a heterosexual world when they acknowledge their attraction to their own gender, and then again when they acknowledge their continuing attraction to the opposite sex. This process is more complex than coming out as homosexual, and typically takes longer. Most gays and lesbians realize they are homosexual in their teens or early 20s. But most people don’t realize they are bisexual until their late 20s.

Once individuals come out as bisexual, they often find it to be socially isolating. Gays and lesbians are much more numerous, with a robust culture that includes publications, meeting places, even neighborhoods in many cities. Bisexuality is comparatively invisible, although the internet has provided a welcome sense of community. (A Google search of the term “bisexual” produces 108 million hits.)

If you’re bisexual, or think you might be, you’re not alone. In addition to Alfred Kinsey, here’s a partial list of famous bisexuals: Singers Lady Gaga, Debby Harry, Janis Joplin, Amy Winehouse, Billie Holiday, and Bessie Smith; actors Marilyn Monroe, Anthony Perkins, Greta Garbo, James Dean, Drew Barrymore, Montgomery Clift, Anne Heche, Laurence Olivier, Lindsay Lohan, and Sal Mineo; writers Oscar Wilde and Gore Vidal; dancers Isadora Duncan and Alvin Ailey; conductor Leonard Bernstein; and artist Frida Kahlo. Learn more about bisexuality here.