Lisa Diamond, an associate professor of psychology and gender studies at the University of Utah, in January of 2008 published the results of a multi-year study of 79 women who did not self-identify as heterosexual. Professor Diamond's research began in 1995 when she conducted in-person interviews with the women, who identified themselves as lesbian, bisexual, or unlabeled but not heterosexual. The women were all between 18 and 25 years old at the time. Diamond then followed up with each woman every two years, in a phone interview. Dr. Diamond was researching the idea of bisexuality as a temporary stage of denial or transition, a stable "3rd type" of sexual orientation, or a heightened capacity for sexual fluidity.

Dr. Diamond discovered that the women who identified as bisexual continued to be attracted to both sexes, which supports the idea that bisexuality is a distinct sexual orientation, rather than a temporary phase, particularly since the study included women in a range of ages. Diamond further suggests that most women "possess the capacity to experience sexual desires for both sexes, under the right circumstances," and discovered that over time, bisexual women were more likely than lesbians to switch between describing themselves as bisexual and unlabeled, rather than to identify as lesbian or heterosexual. Some of the women created their own labels, including one who described herself as "reluctant heterosexual."

The women in the study who identify as heterosexual and who "experiment with same-sex desires and behaviors, but if they really are predominantly heterosexual, they may enjoy experimentation but may not change their sexuality." She also discovered that the women who identified as bisexual tended to be monogamous, and form long-term attachments, thereby debunking another bisexual myth. Roughly a quarter of the women said their choice of sexual partners was not affected by their partner's sex or gender. "Deep down," said one woman, "it's just a matter of who I meet and fall in love with, and it's not their body, it's something behind the eyes."

You can read about Professor Diamond's research in "Female Bisexuality From Adolescence to Adulthood: Results From a 10-Year Longitudinal Study" published in the January 2008 issue of Developmental Psychology, a journal of the American Psychological Association, or see a summary from USA Today.

After her initial study, Dr. Diamond discovered that some of her research was being wrenched out of context, particularly by Christian Right groups who want to argue that sexual orientation was a choice. What Dr. Diamond's research in fact indicated was that rather than being a conscious choice, something that could be controlled, many women experienced their sexual orientation as something that was fluid, a spectrum rather than a grid. By the tenth year of the study, two-thirds of the women had changed their identity label at least once. In subsequent research, Dr. Diamond discovered that "Eighty percent of the identity transitions that I've observed in the 13 years of the study have been transitions to either bisexual or unlabeled identities, from lesbian or heterosexual identities." In fact, current research suggests that "The exclusive categories [of heterosexual or homosexual] are actually the smallest categories, and those bisexual ranges are actually the largest ranges."