Meredith Chivers' Ten Hypotheses

In "The specificity of women's sexual response and its relationship with sexual orientations", Meredith Chivers (2016) proposed the following ten hypotheses as potential explanations for the gender-nonspecific sexual responses of androphilic women:

• [H1] Erotic plasticity: Women are more sexually malleable than men.
• [H2] Preparation hypothesis: Unlike in men, women's bodies automatically respond to any sexual stimulus, in order to protect the vaginal lumen from unwanted sex
• [H3] Sexual objectification of women's bodies: The eroticization of women's bodies in popular media causes all women to develop same-sex sexual attraction
• [H4] Identification with sexual pleasure: Heterosexual women are turned on by lesbian porn, not because they are attracted to other women, but because they identify with the women shown on screen.
• [H5] Fertility-dependent change in specificity of sexual response: Women's sexual response towards men varies with hormonal cycle.
• [H6] Magnitude of sexual response: The magnitude of sexual response to preferred stimuli among heterosexual women is, on average, lower than men's, due to differences in male and female physiology.
• [H7] Early neurohormonal events affect response specificity in adulthood: In addition to sexual orientation, category-specificity is sexually differentiated via prenatal hormones.
• [H8] Gender-specific sexual response reflects "masculine" sexual and nonsexual traits in gynephilic women: In females, masculinization of nonsexual behaviors is accompanied by greater category-specificity of sexual response.
• [H9] Greater variability in sexual rewards among androphilic women: Because women are more likely to orgasm from sex with other women, homosexual women develop stronger sexual preferences for women, but heterosexual women do not develop stronger sexual preferences for men.
• [H10] Nonsexual motivations to attend to sexual stimuli interact with stimulus potency to produce nonspecific response: Women capture the attention of heterosexual women for nonsexual reasons, such as intrasexual competition. 

[H1] Erotic plasticity can be disregarded because it is a "circular argument". [H8] Gender-specific sexual response reflects "masculine" sexual and nonsexual traits in gynephilic women can also be disregarded, because it was tested and disproven (Rieger et al., 2016).

The remaining hypotheses can partially, but not completely, explain androphilic women's lack of gender-specificity. [H3] Sexual objectification of women's bodies does not explain why androphilic men are not aroused by women's bodies. [H4] Identification with sexual pleasure and [H6] Magnitude of sexual response fail to explain why gynephilic women display greater gender-specificity while androphilic women do not. [H10] Nonsexual motivations to attend to sexual stimuli interact with stimulus potency to produce nonspecific response could explain androphilic women's visual attention towards other women, but does not explain why this causes genital arousal. 

[H2] Preparation hypothesis was reviewed by Lalumière et al. (2022), who concluded that "the evidence is favorable but not entirely convincing, and more work is required to reach a firm conclusion". 

[H5] Fertility-dependent change in specificity of sexual response is similar to Diamond's (2008) theory involving proceptivity and arousability. Some evidence in support of this theory has been reported in androphilic and nonheterosexual women (Suschinsky et al., 2014)(Diamond & Wallen, 2011). 

[H7] Early neurohormonal events affect response specificity in adulthood explains why XY CAIS individuals are female-typical in their sexual response, while XX CAH individuals are male-shifted(Hamann et al., 2014)(Meyer-Bahlburg et al., 2008). If gynephilia and gender-specificity can both be caused by male-shifted brain sexual differentiation, this would explain the association between gynephilia and gender-specificity in females. However, it is doubtful that neurohormonal events account for the entirety of this difference, nor is it clear whether this differentiates during the prenatal stage or a different developmental period.

In animal models, "different aspects of neural sexual differentiation may be mediated ["organized"] at different times", including the prenatal, neonatal, and pubertal periods (Burke et al., 2023)(Hines, 2011). Male-typical hormone levels are necessary "across all critical developmental periods" for complete masculinization (Burke et al., 2023). If this is true in humans, it could also be the case that female-typical hormone levels are necessary at all critical periods for complete feminization of sexual behavior and preference. 

If androphilia and gender-nonspecificity are distinct aspects of female sexuality, it could be that androphilic males are only partially feminized in their sexuality, being sexually oriented towards men but not gender-nonspecific. XY CAIS individuals could be more fully feminized, being sexually oriented towards men and female-typical in their gender-nonspecificity.

[H9] Greater variability in sexual rewards among androphilic women suggests that the difference in gender-specificity is not congenital but learned. Contrary to [H7], it is possible that reliability of orgasm reinforces gender-specificity of sexual response. All men and gynephilic women show gender-specific responses because men are more likely to reliably orgasm during sex, and women are more likely to reliably orgasm from sex with other women. Androphilic women are uniquely gender-nonspecific, due to the unreliability of a woman's orgasm during heterosexual intercourse. 

While it is difficult to attribute sex differences in gender-specificity to learning, it is possible that sexual orientation effects between gynephilic and androphilic women are learned. Because women identified as gynephilic are also more likely to have more positive sexual experiences with women, it is unknown whether differences in sexual response are the result of an innate sexual orientation or conditioned from reliable orgasm. However, [H9] does not explain why childhood sex-atypicality predicts gynephilia in women(Tolman, 2018), why the onset same-sex sexual attraction typically predates first same-sex sexual behavior (Savin-Williams & Diamond, 2000)(Fisher, 2012)(McClelland et al., 2015)(de Graaf & Picavet, 2017)(Tolman, 2018), or the higher rate of nonheterosexuality in XX CAH individuals (Meyer-Bahlburg et al., 2008). 

Rather than an "either/or" choice, it is likely that prenatal factors and learning both have a role in shaping sexual orientation.

EDIT: Once again, I neglected to incorporate information from the Commentaries and Chivers' (2017) Response to Commentaries. 

In her Response to Commentaries, Chivers (2017) elaborates on two additional hypotheses proposed by Luoto & Rantala (2017):

• [H11] Nutritional Hypothesis: Women's bodies are sexualized via their association with breastfeeding 
• [H12] Alloparenting: If the father of her children dies or abandons her, it is adaptive for a woman to have the capacity for same-sex relationships.

Like [H3], [H11] Nutritional Hypothesis does not explain why androphilic men are not aroused by women's bodies. Chivers (2017) is skeptical of [H12] Alloparenting, noting that sexual reinforcement of alloparenting favors has not been demonstrated "in any animal species", even bonobos. 

Diamond's (2017) Commentary defends [H4] and [H10], as does Safron & Hoffmann's (2017) Commentary. Indeed, Safron & Hoffmann (2017) raise a thirteenth intriguing hypothesis:

• [H13] Male Homonegativity: "androphilic women may experience relatively reduced social pressure to inhibit responses to nonpreferred stimuli, due to greater homophobia often directed at male, relative to female, same-sex attraction in some cultures"

Chivers (2017) elaborates:

"Sexual fluidity, at least in terms of a capacity to respond to nonpreferred sexual stimuli, may then not be a phenomenon unique to women (Diamond, 2016). We are currently investigating these hypotheses in my laboratory, seeking to understand correlates of genital response to male sexual stimuli in gynephilic men. We have data suggesting that homonegativity is associated with patterns of visual attention to nonpreferred sexual stimuli (Tassone, Dawson, & Chivers, 2017). It could be that gynephilic men modulate genital responses to male sexual stimuli through allocation of attentional resources; genital responses are triggered by prepotent sexual features within male sexual stimuli, and by diverting attention away from these cues, gynephilic men avoid experiencing greater sexual response to nonpreferred stimuli. Safron and Hoffman (2017) proposed similar ideas, suggesting that androphilic women may have fewer incentives to modulate sexual response to female cues than gynephilic men do to male sexual cues."

Average prevalence of sexual orientation categories
Bailey et al (2016)

In theory, [H13] could explain why gynephilic men are more gender-specific than androphilic women, but it fails to explain why androphilic men are more gender-specific in their physiological sexual arousal than gynephilic women. In response to the counterpoint "why are gay men specific?" to which Safron & Hoffmann (2017) respond: "most men are not gay, and there may be population-level filtering effects wherein only the most specific and androphilic men go on to adopt gay identities." 

If [H13] Male Homonegativity is right, we would expect there to be more lesbian-identified women than gay-identified men, due to lower social pressure to inhibit female homosexuality. Instead, research has found that there are more exclusively androphilic men than there are exclusively gynephilic women (Copen et al., 2016)(for review, see Bailey et al., 2016; Semenyna et al., 2022). In Safron & Hoffmann's (2017) description of "population-level filtering effects", they seem to be unaware of the history behind research on male bisexuality. There was a period of time where sex researchers debated the existence of bisexual men, because so many of the "most specific and androphilic men" adopted "bisexual" identities (Rieger et al., 2005). This trend is called "transitional bisexuality", and suggests that the percent of men who are exclusively androphilic is probably even larger than reported (Blanchard, 2023)(Semon et al., 2017). As such, [H13] cannot, on its own, account for the sex difference in specificity of arousal.

Safron & Hoffmann (2017) also defend [H3], raising the following points:

"Firstly, it is not clear that gay men have as much experience looking at sexualized images of women as do androphilic women (e.g., fashion magazines). Secondly, eroticized images of women may be particularly relevant to androphilic women by virtue of social comparison (consistent with Hypothesis 10). Third, object of desire self-consciousness theory suggests that women may self-eroticize...which could potentially contribute to nonpreferred responding."

The above theories suggest that sex differences in specificity of arousal could be due to sociocultural factors instead of biology. Although these are intriguing, "the near-perfect quasi-experiment" suggests otherwise (Bailey et al., 2016). 

Bailey et al. (2016) argued against [H3], stating that, "One possibility is cultural—namely, Western cultures produce omnipresent depictions of female beauty, which are often sexualized, and exposure to these images from an early age may sensitize both men and women to experience sexual arousal to the female body. Although this explanation might account for heterosexual women’s genital arousal to female stimuli, it cannot account for the fact that homosexual men, who have experienced just as much exposure to sexualized images of women, do not experience sexual arousal to female stimuli. Similarly, exposure to sexualized images of women fails to account for the fact that homosexual women show more genital arousal to male sexual stimuli than homosexual men show to female sexual stimuli."

Chivers (2016) makes a similar comment: "gay men are as exposed to sexualized imagery of women, but they do not demonstrate nonspecific sexual response patterns."

Safron & Hoffmann (2017) also defend [H1] from the claim that it is a circular argument, noting that erotic plasticity, nonspecific arousal, and sexual fluidity could have a common mediator of incentive motivation, with circular causation creating positive feedback loops between the three processes.

Safron & Hoffmann's (2017) is brief, but recommended to those with an interest in understanding the mechanisms behind sexual orientation. 

Related Blog Posts

Two Additional Hypotheses to Meredith Chivers' 10 Hypotheses

References

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 (Original work published 2016)

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• Tassone, D., Dawson, S. J., & Chivers, M. L. (2017, April). Homonegativity predicts rapidvisual detection and visual avoidance of non-preferred sexual stimuli in gynephilic men. Poster presented at the meeting of the Society for Sex Therapy and Research, Montreal, PQ.
  
  Tolman, D. (2018). The Cambridge Handbook of Sexual Development. The Cambridge Handbook of Sexual Development. https://doi.org/10.1017/9781108116121