Case Study 10.1: Sexual Fluidity Across the Life Course

Lisa Diamond's Decade-Long Research Program

In the mid-1990s, developmental psychologist Lisa Diamond set out to track the lives of women who identified as lesbian, bisexual, or unlabeled — women whose sexualities already existed outside the mainstream narrative of fixed, lifelong heterosexual orientation. She interviewed them in depth about their attractions, relationships, identity labels, and experiences of desire. Then she came back and did it again. And again. For ten years.

The result was one of the most rigorous longitudinal studies of sexual orientation ever conducted, and its findings, published in the 2008 book Sexual Fluidity: Understanding Women's Love and Desire, challenged assumptions held simultaneously by conservatives, liberals, and LGBTQ+ advocates.

What the Study Found

Diamond recruited 100 young women, aged 16 to 23, at the study's outset. They were drawn from lesbian and bisexual community events, college LGB organizations, and social networks, and they were followed through biennial interviews until 2005. By the final wave, 89 women remained in the study with largely complete data.

The central finding was this: over ten years, about two-thirds of the women changed their self-identified sexual orientation label at least once. These changes were not primarily responses to social pressure — Diamond carefully assessed whether identity shifts tracked changes in actual attraction patterns, and for a majority of those who relabeled, they did. Women who had identified as lesbian reported genuine, sometimes surprising attractions to specific men. Women who had identified as bisexual sometimes experienced years-long periods of predominantly same-sex attraction before attraction to men re-emerged.

Crucially, these changes were not uniformly directional. Women did not simply "convert" toward heterosexuality, as conversion therapy proponents would have hoped. Changes occurred in every direction. And women who adopted the label "unlabeled" — declining to identify as gay, bisexual, or straight — showed, paradoxically, more stability in their underlying attraction patterns than labeled women, perhaps because they were less bound by the identity expectations that come with labels.

Diamond also documented that shifts in attraction were more likely to be triggered by specific relationships and emotional intimacy than by shifts in sexual fantasy. A woman might maintain consistent erotic fantasies while finding herself genuinely attracted to a specific person of a gender she had not previously experienced as attractive. This suggested to Diamond that romantic love and sexual desire — while obviously connected — are not the same system, and that romantic bonding may activate desire in ways that cross the boundaries of dispositional sexual orientation.

What the Media Got Wrong

Diamond's findings were quickly appropriated for purposes she had explicitly warned against. Conservative commentators cited her work as evidence that sexual orientation is a choice and that LGBTQ+ people can and should change their attractions — a conclusion that Diamond rejected forcefully and specifically. Her data showed spontaneous, non-deliberate shifts in attraction, not willed change produced by therapy, religious commitment, or effort. The distinction is critical: something can be malleable without being voluntary.

Progressive voices, meanwhile, sometimes misread the findings as a threat to LGBTQ+ rights — suggesting that if orientation can change, it is somehow less real, less deserving of legal protection. This reading confuses mutability with inauthenticity. Hair color is mutable; it is still real. Desires that evolve over time are still genuine desires at each moment of their expression.

A third misreading came from popular women's magazines, which characterized Diamond's work as proving that "all women are bisexual." Diamond's sample was deliberately drawn from non-heterosexual communities, and her findings cannot be extrapolated to the general population of women.

Challenging Both Fixed-Biology and Pure Social Construction

Diamond's findings sit uncomfortably for partisans on both sides of the nature-versus-nurture debate.

For strict biological determinists — who hold that sexual orientation is fixed at birth (or in prenatal development) and unchanging throughout life — the documented pattern of genuine attraction shifts is difficult to accommodate. The data are not compatible with a model in which sexual orientation is a simple binary trait determined by genetics or prenatal hormone exposure and then frozen.

For pure social constructionists — who hold that sexual orientation is entirely a product of social learning and therefore fully malleable with the right intervention — Diamond's findings also cause problems. The women in her study were not primarily changing their attractions in response to social incentives; if anything, identifying as lesbian in the mid-1990s carried social costs. And the attraction shifts they reported often surprised and unsettled them — they were not produced by cultural expectation but sometimes contradicted it.

What Diamond's model offers is a middle path: sexual orientation as a dispositional tendency (likely with biological underpinnings) that is nonetheless organized through a behavioral and affective system flexible enough to produce genuine change across the life course. The biology is real; so is the plasticity.

Questions for Discussion

1. Diamond's study recruited from non-heterosexual community spaces. How might this sampling choice affect the generalizability of her findings about fluidity? What would a study design look like that could address this limitation?

2. The finding that romantic intimacy can produce attraction across the grain of established orientation patterns has been called the "love trumps orientation" finding. What does this tell us about the relationship between the bonding system and the sexual system? How does it relate to the co-evolutionary model?

3. Diamond's work has been extended (with mixed results) to samples of men, with preliminary findings suggesting that male desire may show less fluidity on average than female desire. If this sex difference is real, what co-evolutionary explanation would you offer? Consider: hormonal differences, social costs of same-sex behavior for men versus women, cultural availability of "bisexual" as a legitimate male identity.