Actress Cynthia Nixon made headlines recently when she said during an interview that she “chooses” to be a lesbian. “I’ve been straight and I’ve been gay, and gay is better,” she said. “For me, it is a choice.” As you might expect, her comments – published in a New York Times Magazine profile - set off a firestorm of controversy, with gay activists and others worrying that Nixon’s words would give credence to those who claim that being gay is a conscious decision, not a genetic certainty. (She later clarified that she identifies most closely as a bisexual, which, she says, is a “fact,” not a choice.) But, divisive wording aside, there may be something to Nixon’s remarks. The actress, who was once in a long-term relationship with a man and who is now engaged to a woman, appears to be an example of what scientists are now terming “sexual fluidity.” In other words, she may be attracted to a specific person rather than a particular gender. It’s a phenomenon that Lisa Diamond, a University of Utah psychology professor, has studied extensively. In her 2008 book, “Sexual Fluidity: Understanding Women’s Love and Desire,” she writes that women’s sexuality appears to be much more fluid than men’s, and that this fluidity tends to involve three main characteristics: – Non-exclusivity in attractions: can find either gender sexually attractive – Changes in attractions: can suddenly find a man or woman sexually attractive after having been in a long-term relationship with the other – Attraction to the person, not the gender Research seems to support the idea that some women are able to move between relationships with both genders without blinking an eye - and that labels matter little. In a 2008 study, Diamond followed 70 lesbian, bisexual, and “unlabeled” women over the course of 10 years. During that decade, two-thirds of the women changed their initial identity labels, and one-third of these changed labels at least twice. And although conventional wisdom suggests that more women would transition out of the bisexual and unlabeled groups and into the more “standard” groups of heterosexuality or homosexuality, this was not the case. As Diamond writes, “More women adopted bisexual/unlabeled identities than relinquished these identities; few bisexual/unlabeled women ended up identifying as lesbian or heterosexual. Overall, the most commonly adopted identity was ‘unlabeled.’” So is sexual fluidity unique to women? Possibly, says sexuality educator Emily Nagoski, author of the "Good in Bed Guide to Female Orgasms." “Making space for fluidity as a legitimate part of sexual orientation would help women, but it surely couldn’t hurt men. Men have some fluidity too, just not as much,” she writes. “It’s different for girls, this sexual orientation thing.” She points to a variety of studies that help bolster this idea: For instance, research in men has found genetic differences that may be associated with homosexuality, but similar inheritability of sexual orientation has not yet been identified in women. Plus, Nagoski adds, “Women’s experience of sexual orientation is more discontinuous and variable than men’s, which more typically emerges early and stays the same over different situations.” So, while most men tend to identify themselves as straight, gay, or bisexual relatively early in life, many women may have relationships with both men and women without choosing a specific sexual orientation. Women may also be more receptive than men to a variety of sexual cues. For their recent book, “A Billion Wicked Thoughts,” neuroscientists Ogi Ogas and Sai Gaddam analyzed a billion web searches, a million websites, a million erotic videos, a million erotic stories, millions of personal ads and tens of thousands of digitized romance novels in order to better understand the sexual differences between men and women. They concluded that a single cue triggers arousal in the male brain, but that women’s brains require multiple cues to become aroused. Similarly, research from the University of Toronto found that while men who identified themselves as heterosexual or homosexual became sexually aroused by straight or gay pornography, respectively, women were much more complicated: Regardless of their identified orientation, straight, gay, and bisexual women became physically aroused by a whole range of sexual imagery, including male–male, male–female, and female–female pornography. They were even turned on by images of mating monkeys, although they didn’t admit it. Of course, we shouldn’t interpret these findings as proof that all heterosexual women are sexually attracted to other women, or to monkeys for that matter. But they do suggest that women may be more capable of finding people and things attractive, no matter what orientation they claim. Perhaps that’s why an estimated 95% of straight men who fantasize about or partake in threesomes are only interested in being with two women, while more heterosexual women are open to adding another woman or man to the mix. In the end, Cynthia Nixon’s comments and the conversation they’ve started may reveal less about the actress’s romantic leanings than our own preconceived notions about sexual orientation. Maybe the lesson here is that love and lust are about people, not about labels - and I think that can only be a good thing.