Over the past several decades, scientists have struggled in fits and starts to get a handle on sexual orientation. Born or bred? Can it change during one's lifetime? A handful of studies in the 1990s, most of them focused on men, suggested that homosexuality is hardwired. In one study, researchers linked DNA markers in the Xq28 region of the X chromosome to gay males. But a subsequent larger study failed to replicate the results, leaving the American Academy of Pediatrics and the American Psychological Association to speculate that sexual orientation probably has multiple causes, including environmental, cognitive, and biological factors.
Today, however, a new line of research is beginning to approach sexual orientation as much less fixed than previously thought, especially when it comes to women. The idea that human sexuality forms a continuum has been around since 1948, when Alfred Kinsey introduced his famous six-point scale, with 0 representing complete heterosexuality, 6 signifying complete homosexuality, and bisexuality in the middle, where many of the men and women he interviewed fell. The new buzz phrase coming out of contemporary studies is "sexual fluidity." "People always ask me if this research means everyone is bisexual. No, it doesn't," says Lisa Diamond, PhD, associate professor of psychology and gender studies at the University of Utah and author of the 2008 book Sexual Fluidity: Understanding Women's Love and Desire. "Fluidity represents a capacity to respond erotically in unexpected ways due to particular situations or relationships. It doesn't appear to be something a woman can control." Furthermore, studies indicate that it's more prevalent in women than in men, according to Bonnie Zylbergold, assistant editor of American Sexuality, an online magazine.
In a 2004 landmark study at Northwestern University, the results were eye-opening. During the experiment, the female subjects became sexually aroused when they viewed heterosexual as well as lesbian erotic films. This was true for both gay and straight women. Among the male subjects, however, the straight men were turned on only by erotic films with women, the gay ones by those with men. "We found that women's sexual desire is less rigidly directed toward a particular sex, as compared with men's, and it's more changeable over time," says the study's senior researcher, J. Michael Bailey, PhD. "These findings likely represent a fundamental difference between men's and women's brains."
This idea, that the libido can wander back and forth between genders, Diamond admits, may be threatening and confusing to those with conventional beliefs about sexual orientation. But when the women she's interviewed explain their feelings, it doesn't sound so wild. Many of them say, for example, they are attracted to the person, and not the gender—moved by traits like kindness, intelligence, and humor, which could apply to a man or a woman. Most of all, they long for an emotional connection. And if that comes by way of a female instead of a male, the thrill may override whatever heterosexual orientation they had.