What is Sexual Fluidity?

There are four phenomena related to sexual orientation: (1) sexual behavior (2) self-reported sexual identity (3) self-reported sexual attraction (4) physiological sexual arousal (Bailey et al., 2016). 

With respect to these four phenomena, Kanazawa (2017) argues that sexual fluidity has three distinct facets: 

1. Nonexclusivity: Sexually oriented towards both sexes, in any of the four phenomena (e.g., bisexual, mostly-heterosexual, mostly-homosexual)
2. Change: Sexual orientation changes over time or in different situations, in any of the four phenomena (e.g., day-to-day changes, longitudinal changes, situational changes)
3. Variance: Any one of the four phenomena is at odds with any of the other four phenomena (e.g., sexual fantasy is different from sexual identity and/or behavior)

Diamond et al. (2020) propose a different scheme, where situational change is separated from day-to-day change:

1. Nonexclusivity: "overall erotic responsiveness to one's less-preferred gender"
2. Situational Change: "situational variability in erotic responsiveness to one's less-preferred gender"
3. Variance: "discrepancy between the gender patterning of one's sexual attractions and the gender patterning of one's sexual partnering"
4. Day-to-Day Change: "instability in day-to-day attractions over time"

While these schemes help clarify the meaning of sexual fluidity, they have some problems.

Kanazawa's (2017) scheme is particularly flawed in how it utilizes all four phenomena relating to sexual orientation. As Bailey et al. (2016) explain, sexual identity and sexual behavior are not always reliable measures of a person's sexual orientation. A homosexual who identifies as "heterosexual" and enters a heterosexual marriage is still homosexual. There are also cases where self-reported sexual attraction is less reliable than physiological sexual arousal. When physiological sexual arousal is well-measured and inconsistent with any of the other four phenomena, physiological sexual arousal is the best measure of sexual orientation in males (Bailey, 2009)(Bailey et al., 2016). On the other hand, physiological sexual arousal is generally not concordant with sexual attraction in women, (Chivers et al, 2010)(Chivers, 2017), possibly due to the differences between female proceptivity and female arousability (Diamond, 2007). Between the two options, it is more sensible to follow Diamond et al.'s (2020) scheme, where "erotic responsiveness" (self-reported sexual attractions) are measured instead of sexual identity or sexual behavior. 

For these reasons, it is questionable whether Variance should be considered an aspect of sexual fluidity. This effectively describes closeted homosexuals and bisexuals as "sexually fluid". Additionally, Nonexclusivity is a redundant term. It is the same as bisexuality when bisexuality is defined to include mostly-heterosexuals and mostly-homosexuals.

Furthermore, Diamond et al.'s (2020) also has several self-admitted limitations, including their reliance on self-reported sexual attraction. The four different facets of sexual fluidity were calculated like so:

1. Nonexclusivity ("overall erotic responsiveness to one's less-preferred gender"): composite index of self-reported sexual attractions to less-preferred gender (1) over the course of the previous year (2) day-to-day, over the course of 2 weeks (3) during laboratory assessement
2. Situational Change ("situational variability in erotic responsiveness to one's less-preferred gender"): standardized residuals from regression analysis to predict each of the three measures described under Nonexclusivity from each of the others
3. Variance ("discrepancy between the gender patterning of one's sexual attractions and the gender patterning of one's sexual partnering"): standardized residuals from regression analysis to predict ratio of sexual partners (sexual behavior) from self-reported sexual attractions
4. Day-to-Day Change ("instability in day-to-day attractions over time"): dynamic (in)stability of self-reported sexual attractions recorded day-to-day, over the course of 2 weeks

Luoto & Rantala (2022) explain the problem with self-reported sexual attraction and identity:

"...assessments of the prevalence or fluidity of women's sexual orientations may be confounded by the person-based nature of many nonheterosexual women's sexual attractions. In contrast to most men, most women require emotional involvement to engage in a sexual relationship...It is therefore important to understand that defining a bisexual woman's sexual orientation merely by asking which sex she is attracted to at an arbitrary point in time may be misleading. One may be erroneously led to believe that her sexual orientation has undergone shifts from heterosexual to homosexual or to bisexual in the course of her life. This is because romantic love causes one to focus one's energy and attention solely on the object of one's love...Should the love object be male, the woman might be inclined to identify as heterosexual. Should the love object be female, the woman may be inclined to identify as homosexual. If feelings of romantic love towards that person subside, the woman's "momentary sexual orientation" may undergo another shift, giving a muddled view about her sexual orientation. This does not ultimately boil down to sexual malleability nor to fundamental changes in the woman's sexual orientation...but to the fact that nonheterosexual women's attractions are sometimes person-based rather than sex-based...Determining women's sexual orientation through an introspective sense of their sexual orientation at an arbitrary point in time can therefore be problematic if a person-based attraction should at that specific point in time bias it to one end of the male-female gender spectrum." 

In addition to other Limitations, Diamond et al.'s (2020) admit there are "inherent weaknesses" to self-reported measures and that their study involved a small sample size. Due to its low statistical power and reliance on self-report, it is premature to conclude that these measures of sexual fluidity are truly distinct from female bisexuality (Nonexclusivity).

In spite of these limitations, I would argue that Situational Change is a meaningful concept. Women of all sexual orientations seem to show Situational Change (Diamond et al., 2020), possibly due to the fact that many women's attractions are "person-based" instead of "sex-based" (Diamond, 2014)(Luoto & Rantala, 2022). Women's variability in Situational Change could also arise from sex differences in response to the visual stimuli presented during laboratory assessment (Rupp & Wallen, 2008)(Rupp & Wallen, 2009). Situational Change is at least meaningful as "person-based"-ness, where it is conceptualized as a distinct dimension from attraction to the sexes. Women show varying levels of "person-based" attraction, just as they show varying levels of androphilia and gynephilia. It is possible that Situational Change can also be expanded to different situations or contexts from the ones studied by Diamond et al. (2020). Either way, Situational Change is probably sex-typed characteristic, with differences between the sexes and sexual orientation effects.

Day-to-Day Change is also a well-defined facet of sexual fluidity that is distinct from bisexuality. Women also show greater Day-to-Day Change than men, as do bisexuals compared to other sexual orientations (Diamond et al., 2017). This facet of sexual fluidity could probably be expanded to Temporal Change, itself being a multifaceted concept that includes (1) Day-to-Day Change (2) Longitudinal Change (3) Cyclical Change. Indeed, Diamond et al. (2020) note that Longitudinal Change is probably another important facet to sexual fluidity which they were unable to assess due to the study's limitations. Longitudinal Change has been reported in women of various sexual orientations, but is more common in bisexuals or 'fluid lesbians' than 'stable lesbians' (Diamond, 2005)(Savin-Williams et al., 2012)(Diamond, 2016). Cyclical Change is also a feature of women's sexuality due to the hormonal cycles of female biology (Diamond & Wallen, 2011)(Suschinsky et al., 2014)(Slob et al., 1991)(Wallen & Rupp, 2010). 

When sexual fluidity is defined in terms of Situational Change and Temporal Change, it is overlaps with but is distinct from bisexuality, and is an important concept with respect to female sexuality.

Sexually Fluid, or Nonoriented? 

Women's sexuality is characterized by nonexclusivity (bisexuality), and sexual fluidity (Situational Change and Temporal Change), along with "person-based" attraction and nonspecificity. If women's attractions are nonexclusive, nonspecific, "person-based" and sexually fluid, does it make sense to conceptualize these as different traits, or "ought these dispositions be considered to reflect the absence of orientations" (Safron & Hoffmann, 2017) ?

Notably, most of Lisa Diamond's research has examined fluidity of self-reported sexual identity or sexual attractions instead of physiological sexual arousal. As Diamond & Rosky (2016) note that sexually fluidity "appears less common among individuals with exclusive attractions than those with bisexual attractions", are they correct in assuming sexual orientation is not immutable, or have they merely demonstrated that self-reported sexual identity and sexual attractions are subject to change? Raines et al. (2021) reported a change in physiological sexual arousal that accompanied a rather large change in self-reported sexual attractions (mostly-gynephilic to mostly-androphilic), but they neglected to describe the size of the change in physiological sexual arousal. As such, it is not clear whether physiological sexual arousal is as variable as self-reported sexual identity or sexual attractions in females.

Diamond (2016) explains the difference between sexual fluidity and bisexuality (nonexclusivity) like so: 

"One of the most common questions about sexual fluidity is "How does it differ from bisexuality?" After all, both sexual fluidity and bisexuality produce the same phenomenological result: sexual attractions for both men and women (although not always concurrently). The primary difference between sexual fluidity and bisexuality is that the latter is conceptualized as a stable sexual predisposition giving rise to consistent experiences of nonexclusive desires (i.e., desires for both men and women) over the life course. In contrast, sexual fluidity is conceptualized as a capacity for change in erotic responsiveness. For some individuals, this capacity may never be expressed. Others may only encounter one or two circumstances over their lifespan which give rise to changes in sexual feelings. Hence, although both bisexuality and sexual fluidity can produce nonexclusive sexual attractions, such attractions are expected to be a regular feature in the lives of bisexually oriented individuals, whereas they may prove more sporadic and/or context-specific for individuals who are highly sexually fluid."

I'm not sure if I agree with the description of bisexuality as "a stable sexual predisposition giving rise to consistent experiences of nonexclusive desires" (see aforementioned quote from Luoto & Rantala, 2022). 

Diamond et al. (2017) write: 

How Does Sexual Fluidity Differ from Bisexuality? 

Sexual fluidity has been defined as a capacity for change in attractions which results from an individual’s heightened erotic sensitivity to situational and contextual influences (Diamond, 2008b). In contrast, bisexuality is typically defined as the experience of (or capacity for) sexual attractions to both sexes, even if an individual ‘‘leans’’ more strongly toward one sex than the other (Diamond, 2008a; Rosenthal, Sylva, Safron, & Bailey, 2012). Conceptually, the key distinction between sexual fluidity and bisexuality concerns change in attractions. The potential for change in attractions is a defining feature of sexual fluidity, but not necessarily of bisexuality. Research indicates that bisexual orientations may be just as enduring and biologically based as exclusive same-sex orientations (Bailey, Dunne, & Martin, 2000; Diamond, 2008a). Yet empirically, it is often difficult to distinguish between sexual fluidity and bisexuality given that the most salient observable manifestation of sexual fluidity is a shift from exclusive to nonexclusive attractions (for example, a heterosexual woman unexpectedly developing same-sex attractions or a lesbian woman developing other-sex attractions, as in Diamond, 2008b). Individuals who describe their sexuality as‘‘fluid’’ frequently report transitions to bisexual attractions, bisexual behavior, and even bisexual identification (Diamond, 2008b; Katz-Wise, 2015; Kinnish et al., 2005; Weinberg et al., 1994).

How, then, can researchers distinguish between sexual fluidity and bisexuality? Maybe all individuals who perceive that their attractions have changed and expanded over time are simply bisexual (without being aware of it). Answering this question is important for informing our basic understanding of gender and sexual orientation. For example, some researchers have argued that bisexual orientations—in both men and women—are fundamentally more ‘‘open’’ and flexible than exclusive same-sex or other-sex orientations(Ross, Daneback, & Månsson, 2012; Weinberg et al., 1994). If this is the case, then it might be more accurate to view sexual fluidity as a consequence of bisexual attractions, rather than viewing bisexual attractions as a consequence of fluidity.

A similar discussion is found in Diamond et al. (2020): 

Theoretically, a capacity for bisexual attractions may predispose individuals to sexual fluidity given that situational, interpersonal, and contextual factors may “push” bisexual attractions toward one gender over another at different points in time. This is consistent with the fact that bisexually attracted individuals report more longitudinal change in their attractions than exclusively attracted individuals (Diamond, 2008b, 2016), less day-to-day stability in sexual attractions (Diamond, Dickenson, & Blair, 2017), and more genital arousal to their less-preferred gender in the laboratory (Chivers, Bouchard, & Timmers, 2015). Hence, one might argue that sexual fluidity is simply an outgrowth of bisexuality, consistent with the common notion that bisexual orientations are fundamentally more “open” and flexible than exclusive same-sex or other-sex orientations (Ross, Daneback, & Månsson, 2012; Weinberg, Williams, & Pryor, 1994). 

Although Diamond et al. (2020) found differences between sexual fluidity and bisexuality (see aforementioned discussion), this study relied on self-report. They have failed to consider the possibility that the sexually fluid respondents were bisexual (nonexclusive) all along, "without being aware of it". 

Studying "self-reported sexual attraction to each gender", Diamond et al. (2017) found that bisexuals showed lower day-to-day stability in attractions to "less-preferred" gender, but not "more-preferred" gender: 

We found that women showed lower day-to-day stability than men for attractions to both the ‘‘more-preferred’’ and ‘‘less-preferred’’ gender, suggestive of a generalized gender difference in erotic sensitivity to context. Yet individuals with bisexual patterns of attraction only showed lower day-to-day stability in their attractions to the ‘‘less-preferred’’ gender. This finding is consistent with other research arguing that a fundamental difference between individuals with bisexual versus exclusive patterns of attraction concerns the nature of their attractions to the‘‘less-preferred’’ gender. As summarized by Rieger et al. (2005), bisexuals as a group show stronger attractions to their less-preferred gender than do exclusively attracted individuals, and hence smaller gaps between the magnitude of their more-preferred and less preferred attractions. The present research expands this characterization by showing that the‘‘less-preferred’’ attractions of bisexual individuals are also less stable (at a day-today level) than those of exclusively attracted individuals, showing less of a tendency to gravitate toward a person-specific‘‘setpoint.’’

 Yet when it came to the day-to-day stability of attractions to the more-preferred gender, bisexually attracted individuals showed  as much stability as did exclusively attracted individuals. Hence, these findings do not support a notion of bisexuals as globally flexible and variable in their attractions. Rather, it is their daily attractions to the less-preferred gender that render them distinct from exclusively attracted men and women. They also proved distinct from exclusively attracted individuals in their retrospective changes: Bisexually attracted individuals recalled larger post adolescent changes in attractions to both the more-preferred and less-preferred gender. As noted earlier, such changes may have different determinants than day-to-day changes, underscoring the importance of future research incorporating measures of both short-term and long-term changes in attractions, and which differentiates between assessments of the magnitude versus the temporal patterning of change.

The above suggests that the assumption that bisexuality is "a stable sexual predisposition giving rise to consistent experiences of nonexclusive desires" appears to be faulty. As such, I am no longer certain that female sexual fluidity (Situational Change and Temporal Change) describe different phenomena from female bisexuality (nonexclusivity), or if these are merely outgrowths of women being "nonoriented" (Bailey, 2009). 

Where I describe women as "nonoriented", I am referring to "heterosexual" or "androphilic" women, who are the majority group. I think it is more accurate to describe gynephilic women as "weakly oriented", where they are not as "nonoriented" as androphilic women but more "nonoriented" than men. 

Related Blog Posts

Stable Lesbians' Attractions are not Person-Based

Lisa Diamond's Four Elements of Sexual Fluidity

Stable vs. Fluid Lesbians

References

Bailey, J. M. (2009). What is sexual orientation and do women have one?. In Contemporary perspectives on lesbian, gay, and bisexual identities (pp. 43-63). New York, NY: Springer New York. https://doi.org/10.1007/978-0-387-09556-1_3

Bailey, J. M., Dunne, M. P., & Martin, N. G. (2000). Genetic and environ mental influences on sexual orientation and its correlates in an Australian twin sample. Journal of Personality and Social Psychology, 78, 524–536. doi:10.1037/0022-3514.78.3.524.

Bailey, J. M., Vasey, P. L., Diamond, L. M., Breedlove, S. M., Vilain, E., & Epprecht, M. (2016). Sexual orientation, controversy, and science. Psychological science in the public interest, 17(2), 45-101. https://doi.org/10.1177/1529100616637616

Chivers, M. L. (2017). The specificity of women’s sexual response and its relationship with sexual orientations: A review and ten hypotheses. Archives of Sexual Behavior, 46(5), 1161-1179. https://doi.org/10.1007/s10508-016-0897-x

Chivers, M. L., Bouchard, K., & Timmers, A. D. (2015). Straight but not narrow: Within-gender variation in the gender-specificity of women’s sexual response. PLoS ONE, 10(12), e0142575. https :// doi.org/10.1371/journ al.pone.01425 75.

Chivers, M. L., Seto, M. C., Lalumière, M. L., Laan, E., & Grimbos, T. (2010). Agreement of self-reported and genital measures of sexual arousal in men and women: A meta-analysis. Archives of sexual behavior, 39(1), 5-56. https://doi.org/10.1007/s10508-009-9556-9

Diamond, L. M. (2005). A new view of lesbian subtypes: Stable versus fluid identity trajectories over an 8-year period. Psychology of Women Quarterly, 29(2), 119-128. https://doi.org/10.1111/j.1471-6402.2005.00174.x 

Diamond, L. M. (2007). The evolution of plasticity in female-female desire. Journal of Psychology & Human Sexuality, 18(4), 245-274. https://doi.org/10.1300/J056v18n04_01

Diamond, L. M. (2008a). Female bisexuality from adolescence to adult hood: Results from a 10yearlongitudinal study. Developmental Psychology, 44, 5–14. doi:10.1037/0012-1649.44.1.5. 

Diamond, L. M.(2008b). Sexual fluidity: Understanding women’s love and desire. Cambridge, MA: Harvard University Press.

Diamond, L. M. (2014). Gender and same-sex sexuality. In D. L. Tolman, L. M. Diamond, J. A. Bauermeister, W. H. George, J. G. Pfaus, & L. M. Ward (Eds.), APA handbook of sexuality and psychology, Vol. 1. Person-based approaches (pp. 629–652). American Psychological Association. https://doi.org/10.1037/14193-020

Diamond, L. M. (2016). Sexual fluidity in male and females. Current Sexual Health Reports, 8(4), 249-256. https://doi.org/10.1007/s11930-016-0092-z

Diamond, L. M., Alley, J., Dickenson, J., & Blair, K. L. (2020). Who counts as sexually fluid? Comparing four different types of sexual fluidity in women. Archives of Sexual Behavior, 49(7), 2389-2403. https://doi.org/10.1007/s10508-019-01565-1

Diamond, L. M., Dickenson, J. A., & Blair, K. L. (2017). Stability of sexual attractions across different timescales: The roles of bisexuality and gender. Archives of Sexual Behavior, 46(1), 193-204. https://doi.org/10.1007/s10508-016-0860-x

Diamond, L. M., & Rosky, C. J. (2016). Scrutinizing immutability: Research on sexual orientation and US legal advocacy for sexual minorities. The Journal of Sex Research, 53(4-5), 363-391.

Diamond, L. M., & Wallen, K. (2011). Sexual-minority women’s sexual motivation around the time of ovulation. Archives of Sexual Behavior, 40, 237–246. https://doi.org/10.1007/s10508-010-9631-2

Kanazawa, Satoshi (2017) Possible evolutionary origins of human female sexual fluidity. Biological Reviews, 92 (3). pp. 1251-1274. ISSN 1464-7931. https://doi.org/10.1111/brv.12278

Katz-Wise, S. L. (2015). Sexual fluidity in young adult women and men: Associations with sexual orientation and sexual identity development. Psychology & Sexuality, 6(2), 189–208. doi:10.1080/19419899.2013.876445.

Kinnish, K. K., Strassberg, D. S., & Turner, C. W. (2005). Sex differences in the flexibility of sexual orientation: A multidimensional retrospective assessment. Archives of Sexual Behavior, 34 (2),173–183. doi:10.1007/s10508-005-1795-9.

Luoto S, Rantala MJ. Female Bisexuality. In: Shackelford TK, ed. The Cambridge Handbook of Evolutionary Perspectives on Sexual Psychology. Cambridge Handbooks in Psychology. Cambridge University Press; 2022:94-132.

Raines, J., Holmes, L., Watts-Overall, T. M., Slettevold, E., Gruia, D. C., Orbell, S., & Rieger, G. (2021). Patterns of genital sexual arousal in transgender men. Psychological Science, 32(4), 485-495. https://doi.org/10.1177/0956797620971654 

 Rieger, G., Bailey, J. M., & Chivers, M.L. (2005). Sexual arousal patterns of bisexual men. Psychological Science, 16, 579–584.

Rosenthal, A. M., Sylva, D., Safron, A., & Bailey, J. M. (2012). The male bisexuality debate revisited: Some bisexual men have bisexual arousal patterns. Archives of Sexual Behavior, 41, 135–147.

Ross, M. W., Daneback, K., & Månsson, S.-A. (2012). Fluid versus fixed: A new perspective on bisexuality as a fluid sexual orientation beyond gender. Journal of Bisexuality, 12 (4), 449–460. doi:10.1080/15299716.2012.702609.

Rupp, H. A., & Wallen, K. (2008). Sex differences in response to visual sexual stimuli: A review. Archives of sexual behavior, 37(2), 206-218. https://doi.org/10.1007/s10508-007-9217-9

Rupp, H. A., & Wallen, K. (2009). Sex-specific content preferences for visual sexual stimuli. Archives of Sexual Behavior, 38(3), 417-426. https://doi.org/10.1007/s10508-008-9402-5

Safron, A., & Hoffmann, H. (2017). What does sexual responsiveness to one’s nonpreferred sex mean?. Archives of Sexual Behavior, 46(5), 1199-1202. https://doi.org/10.1007/s10508-017-0954-0

Savin-Williams, R. C., Joyner, K., & Rieger, G. (2012). Prevalence and stability of self-reported sexual orientation identity during young adulthood. Archives of sexual behavior, 41(1), 103-110. https://doi.org/10.1007/s10508-012-9913-y

Slob, A. K., Ernste, M., & Van der Werff ten Bosch, J. J. (1991). Menstrual cycle phase and sexual arousability in women. Archives of Sexual Behavior, 20(6), 567-577. https://doi.org/10.1007/BF01550955

Suschinsky, K. D., Bossio, J. A., & Chivers, M. L. (2014). Women's genital sexual arousal to oral versus penetrative heterosexual sex varies with menstrual cycle phase at first exposure. Hormones and Behavior, 65(3), 319-327. https://doi.org/10.1016/j.yhbeh.2014.01.006

Wallen, K., & Rupp, H. A. (2010). Women's interest in visual sexual stimuli varies with menstrual cycle phase at first exposure and predicts later interest. Hormones and behavior, 57(2), 263-268. https://doi.org/10.1016/j.yhbeh.2009.12.005

Weinberg, M.S., Williams, C.J., & Pryor, D.W. (1994). Dual attraction: Understanding bisexuality. New York: Oxford University Press