Testing Biological Theories of Same-Sex Sexual Attraction and Transgender Identity: Somatic, Cognitive, Behavioural, and Demographic Markers

性别认同和性取向是性别心理上最大的两个差异。绝大多数人是顺性别(即男性认同为男性，女性认同为女性)，并表现出异性吸引力。然而，这些基本模式存在例外。相当多的少数人表现出同性的性吸引和/或变性者，因此为研究大脑、认知和行为的性别分化提供了独特的人类模型。荷尔蒙、遗传和免疫过程被假设为影响大脑的性别分化，并导致性别认同和性取向的性别差异。以前的研究考察了这些生物过程的躯体、认知、行为和人口统计学标志是否一方面区分了变性人和顺性人，另一方面也吸引了同性和异性。与变性人有关的生物标记物通常也与同性的性吸引有关。然而，由于没有研究直接比较同性吸引顺性和跨性别者的这些生物标志物，目前还不清楚这两种表型在多大程度上(如果有的话)受到不同生物过程的支持。*为了澄清这个问题，我们必须研究一个群体，在这个群体中，比较吸引顺性和跨性别者的群体是可行的。在西方国家，变性者很少见，而且很难在专科诊所之外进行研究。因此，拟议的研究将设在泰国，那里的顺性同性吸引相对普遍(2%-5%)，由于缺乏对性别表达的社会谴责，变性人同性吸引的发生率是其他人群的50至250倍。因此，泰国人口提供了一个难得的机会来比较同性性取向和变性者作为人类性别分化的模型。*泰国同性吸引顺性人和变性人的个体将在一套全面的相关生物标志物上进行比较。这些指标包括与产前雄激素暴露有关的几个指标：大脑结构(如皮质厚度、脑白质微结构)、二至四指比率、身体大小(如身高、体重)、脸部结构、认知能力(如心理旋转)和行为特征(如惯用手)。为了深入了解遗传和免疫因素，我们将分别检查跨性别者和同性性取向的熟悉度和参与者的出生顺序。*通过在一套全面的生物标记物上比较吸引顺性和变性者的同性个体，我的研究项目将改变我们对这些各自的人体模型和生物标记物如何揭示大脑、认知和行为的性别分化的理解。

Gender identity and sexual orientation are two of the largest psychological sex differences. The vast majority of people are cisgender (i.e., males identify as men, females identify as women) and exhibit opposite-sex attraction. Yet, exceptions to these fundamental patterns exist. Substantial minorities of people exhibit same-sex sexual attraction and/or transgenderism and, thus, provide unique human models for studying sexual differentiation of the brain, cognition, and behaviour.******Hormonal, genetic, and immunological processes have been hypothesized to influence sexual differentiation of the brain and lead to within-sex variation in gender identity and sexual orientation. Previous research examined whether somatic, cognitive, behavioural, and demographic markers of these biological processes differentiate transgender vs. cisgender individuals on the one hand, and same- vs. opposite-sex attracted individuals on the other. Biomarkers associated with transgenderism are often also associated with same-sex sexual attraction. Yet, because no studies directly compared these biomarkers across same-sex attracted cisgender vs. transgender individuals, it is unclear to what extent, if any, these two phenotypes are underpinned by different biological processes.******To clarify this issue, one must examine a population in which comparing groups of same-sex attracted cisgender vs. transgender individuals is feasible. In Western countries, transgenderism is rare and difficult to study outside of specialty clinics. Hence, the proposed research will be situated in Thailand where cisgender same-sex attraction is relatively common (2-5%) and, due to a lack of social censure regarding gender expression, transgender same-sex attraction is 50 to 250 times more common than in other populations. Thus, the Thai population provides a rare opportunity to compare same-sex sexual orientation and transgenderism as human models of sexual differentiation.******Thai same-sex attracted cisgender vs. transgender individuals will be compared on a comprehensive set of relevant biomarkers. These include several markers linked to prenatal androgen exposure: brain structure (e.g., cortical thickness, white matter microstructure), second-to-fourth digit ratio, physical size (e.g., height, weight), face structure, cognitive abilities (e.g., mental rotation), and behavioural characteristics (e.g., handedness). To provide insight regarding genetic and immunological factors, familiality of transgenderism and same-sex sexual orientation and participants' birth orders will be examined, respectively.******By comparing same-sex attracted cisgender vs. transgender individuals on a comprehensive set of biomarkers, my research program will transform our understanding of how these respective human models and biomarkers shed light on sexual differentiation of the brain, cognition, and behaviour.**