Butch-Femme Identity and Visuospatial Performance Among Lesbian and Bisexual Women in China

Carving the Biodevelopment of Same-Sex Sexual Orientation at Its Joints

Sexual orientation is a core aspect of human experience and understanding its development is fundamental to psychology as a scientific discipline. Biological perspectives have played an important role in uncovering the processes that contribute to sexual orientation development. Research in this field has relied on a variety of populations, including community, clinical, and cross-cultural samples, and has commonly focused on female gynephilia (i.e., female sexual attraction to adult females) and male androphilia (i.e., male sexual attraction to adult males). Genetic, hormonal, and immunological processes all appear to influence sexual orientation. Consistent with biological perspectives, there are sexual orientation differences in brain development and evidence indicates that similar biological influences apply across cultures. An outstanding question in the field is whether the hypothesized biological influences are all part of the same process or represent different developmental pathways leading to same-sex sexual orientation. Some studies indicate that same-sex sexually oriented people can be divided into subgroups who likely experienced different biological influences. Consideration of gender expression in addition to sexual orientation might help delineate such subgroups. Thus, future research on the possible existence of such subgroups could prove to be valuable for uncovering the biological development of sexual orientation. Recommendations for such future research are discussed.

Mental rotation task performance in relation to sexual and gender diversity in Thailand

Neurohormonal theory argues that organizational effects of hormone exposure influence sexual orientation and gender identity, as well as sex differences in visuospatial cognition. This study examined mental rotation task (MRT) performance in a diverse Thai sample (N = 980). Thai culture has several third genders: individuals assigned male at birth (AMAB) who are feminine and attracted to cis men (i.e., sao praphet song); individuals assigned female at birth (AFAB) who are masculine and attracted to feminine individuals (i.e., toms); AFAB individuals who are feminine and attracted to toms (i.e., dees); and sexual orientation categories similar to Western culture (e.g., gay, lesbian, bi). On the MRT, straight cis men outperformed straight cis women. Results were consistent with organizational effects among AMAB individuals, with straight cis men outperforming gay cis men and sao praphet song. Among AFAB individuals, however, only bi and lesbian cis women outperformed dees. Overall, support for neurohormonal theory was limited among AFAB individuals, but MRT performance among AMAB individuals was consistent with organizational effects. This study informs our understanding of visuospatial sex/gender differences and the applicability of neurohormonal theory across cultures.

A Life History Approach to the Female Sexual Orientation Spectrum: Evolution, Development, Causal Mechanisms, and Health

Women's capacity for sexual fluidity is at least as interesting a phenomenon from the point of view of evolutionary biology and behavioral endocrinology as exclusively homosexual orientation. Evolutionary hypotheses for female nonheterosexuality have failed to fully account for the existence of these different categories of nonheterosexual women, while also overlooking broader data on the causal mechanisms, physiology, ontogeny, and phylogeny of female nonheterosexuality. We review the evolutionary-developmental origins of various phenotypes in the female sexual orientation spectrum using the synergistic approach of Tinbergen's four questions. We also present femme-specific and butch-specific hypotheses at proximate and ultimate levels of analysis. This review article indicates that various nonheterosexual female phenotypes emerge from and contribute to hormonally mediated fast life history strategies. Life history theory provides a biobehavioral explanatory framework for nonheterosexual women's masculinized body morphology, psychological dispositions, and their elevated likelihood of experiencing violence, substance use, obesity, teenage pregnancy, and lower general health. This pattern of life outcomes can create a feedback loop of environmental unpredictability and harshness which destabilizes intrauterine hormonal conditions in mothers, leading to a greater likelihood of fast life history strategies, global health problems, and nonheterosexual preferences in female offspring. We further explore the potential of female nonheterosexuality to function as an alloparental buffer that enables masculinizing alleles to execute their characteristic fast life history strategies as they appear in the female and the male phenotype. Synthesizing life history theory with the female sexual orientation spectrum enriches existing scientific knowledge on the evolutionary-developmental mechanisms of human sex differences.