Evidence that Bisexuality in Women is a Third Sexual Orientation, not a Transitional Stage

A longitudinal study published in 2009 found evidence that bisexuality was a stable sexual orientation and that bisexuals were as likely as lesbian or heterosexual women to commit to long-term relationships.

The study, authored by Lisa M. Diamond, investigated whether bisexuality was best considered a transitional stage, a third sexual orientation, or the result of increased sexual fluidity in women.

The study follows up on a previous experiment authored by Lisa M. Diamond in 2000. In that study, the author examined the changes in sexual attraction, behavior, and identity of 80 lesbian, bisexual and “unlabeled” women for two years. She found that although these women changed their sexual identities and sexual behavior, their sexual attractions remained fairly constant. As the author explains,

“although sexual attractions appear fairly stable, sexual identities and behaviors are more fluid. This fluidity may be an inevitable consequence of the fact that most young women in this sample […] experience attractions for both sexes. This nonexclusivity leaves open the possibility for multiple identities and behaviors over time, even when attractions remain stable.”

According to the transitional model of bisexuality, bisexuality is merely a phase in which people experiment with their sexuality until they develop a heterosexual or lesbian orientation. For these so-called “bi-curious” individuals, bisexuality is an intermediate sexuality that eventually develops into either an exclusively same-sex or exclusively other-sex orientation. In contrast, the the third orientation model views bisexuality as its own unique orientation, like heterosexuality and lesbianism. Finally, others view bisexuality as a poignant manifestation of the sexual fluidity which all individuals are capable of.

The study collected data from 79 bisexual, lesbian, and “unlabeled” women for ten years.

The results supported both the third orientation model and the sexual fluidity model of bisexuality, but not the transitional model. As the author reports,

“Over 10 years, 2/3 of women changed the identity labels they had claimed at the beginning of the study […] Yet, contrary to the ‘transitional stage’ model, more women adopted bisexual/unlabeled identities than relinquished these identities.”

Furthermore, 92% of the women that identified themselves as bisexual or unlabeled at the beginning of this study still identified themselves as bisexual or unlabeled at the conclusion of this study, ten years later. According to the transitional model, as women discover their “true” identities, the rate of bisexuality should decrease, but the opposite appears to be true. Women were more likely to change their sexual identity to bisexual or unlabeled than to lesbian or heterosexual.

As expected, bisexual and unlabeled women had a lower percentage of same-sex attractions than lesbian women. Overall, this difference was consistent over years. Although, from year to year, bisexual women were more likely to have fluctuations in their preferences for same-sex or other-sex partners.

Bisexuality no doubt does represents a transition or period of questioning for many women, but the results of this study clearly indicate that this is not universality applicable.

Identity change more common than identity stability

One of the interesting findings of this study was that change in sexual identity was more common than identity stability. 67% of the women in this study changed their sexual identity at least once and 36% changed their identity more than once. This finding supports the “sexual fluidity” model, which claims that women have the capacity to be attracted to both sexes. As their life circumstances and relationships change over time, women change their sexual identity to more accurately reflect their personal attractions and relationships.

Bisexuality and Monogamy

One of the stereotypes of bisexual or “bi-curious” women is that they cannot commit to long-term relationships. The current study makes such assumptions doubtful.

As the author explains,

“By the 10-year point, more than 60% of the […] bisexuals were involved in relationships lasting longer than 5 years, and 30% had undergone either conventional marriages or commitment ceremonies.”

In fact, the bisexuals were more likely to be in a monogamous relationship by the end of this study than the lesbian, unlabeled, or heterosexual women.


Diamond, L.M. (2000). Sexual identity, attractions, and behavior among young sexual-minority women over a 2-year period. Developmental Psychology, Vol 36, No 2: 241-250.

Diamond, L.M. (2009). Female bisexuality from adolescense to adulthood: Results from a 10-year longitudinal study. Developmental Psychology, Vol 44, No 1: 5-14.