SEGM Guide


Dianna T Kenny

In the Booker prize winning book, Shuggie Bain, author, Douglas Stuart, describes his experience growing up “not like a normal boy” in the unforgiving slums of East Glasgow in Thatcher’s 1980s. As he slowly awakens to the reality that he is not like other boys, 

“[h]e… tried to find something masculine to admire about himself: the black curls, the milky skin, the high bones in his cheeks. He caught the reflection of his own eyes in the mirror. It wasn’t right. It wasn’t how real boys were built to be” (p. 11).

With no one to guide him, Shuggie struggles with the gulf between himself and society’s expectations of masculinity. His brother, Alexander, tries to show him how to walk like a man; he feigns an interest in football and memorizes football statistics in an attempt to “fit in.” Despite his efforts to “fit in” with the other boys in his street, there was nothing he loved more than playing with his mother’s clothes and makeup. These attempts hint at Shuggie’s misapprehensions of masculinity. Shuggie was aware of the difference between himself, his brother, and his peers, but he did not grasp the essence of this difference until many years later. He just knew, as did those around him, that something was “no’ right.” Despite his most earnest wish, his mother would never be cured of her alcoholism and Shuggie was never going to grow up a “normal boy.”

Sexual orientation is one of the developmental achievements that contributes to sexual identity. The four components comprising sexual identity are 

  • understanding of biological sex
  • adoption of a gender identity
  • social sex-role, and
  • sexual orientation. In turn, sexual orientation comprises four dimensions:


    1. sexual attractions(i.e., recognition of those towards whom one feels sexually attracted)[1]
    2. initiation of sexual relationships
    3. disclosure of sexual orientation to others
    4. identity labelling as heterosexual, lesbian/gay or bisexual.[2]More recently, the absence of sexual attraction to either sex has been identified as asexual.[3]

There has been increased interest in understanding how sexual orientation develops across the lifespan but most of the literature in this area involves adolescents and young adults.  Adolescence is considered a pivotal period for the development of sexual orientation.[4] The average age of beginning awareness of same-sex attraction has been estimated at 10 years, following the psychophysiological changes associated with adrenal puberty.[5] However, estimates vary across studies. In one study, the average age of first self-labelling (i.e., as a minority sexual orientation) occurred between 14 and 21. .8 The process of “coming out” (i.e., sexual identity development as lesbian, gay, or bisexual and announcing this orientation to parents, friends ) has been occurring at younger ages than in previous generations, with boys generally reporting knowledge of their minority sexual orientation at younger ages than girls.[6] The reason for this focus in the literature on adolescence is that issues related to sexual orientation are considered unlikely to arise in young children because the concepts outlined above that underpin the concept of sexual orientation will not have developed in the preschool or early primary years; indeed, they usually do not emerge until the child is entering late childhood/early adolescence and has appropriate life experience to understand the biological and social phenomena that are necessary for such an understanding to develop. For some young people, this awareness does not develop until late adolescence and for some, early adulthood. 

Notwithstanding, we have some inklings from novels that homosexual awakening may occur in very young children. A potent example can be found in Christos Tsiolkas’s autobiographical book, 71/2 (2021), in which he describes the lush sensual memories of his five-year-old self of his love for his father’s friend, Stavros, and how these feelings were ignited by other young men with whom he came into contact. Tsiolkas depicts an encounter with a young man in church. 

I stared across at a young man… who had his sleeves folded up on his forearms and the skin is dark and I want to kiss it. I knew that I wanted to kiss it. I wanted to know what it would feel like to rub my lips across the fine black hairs on that arm… Is it possible that even at this tender age I had a premonition of sin? … I knew shame. I saw that God was watching me and I knew that I was tempted by the shaved skin of the men I had looked down on when I was hoisted in my father’s arms.

Homosexuality is currently considered a normal variant of human sexuality. As such, it appears to be a stable polygenic[7] (i.e., multiple genes contributing to a characteristic) trait that occurs on a continuum from bisexual, to mostly gay to exclusively gay.[8] A similar continuum has been identified for mostly to exclusively heterosexual.2

The formation of a minority sexual orientation identity involves four steps: 

  • recognition of same-gender sexual attractions, 
  • initiation of same-sex, intimate relationships, 
  • disclosure of a non-heterosexual sexual orientation to others, and 
  • identification as LGB.[9]The timing of human developmental processes including the development of sexual orientation is varied, as is the order and timing in which these events occur.[10]However, there are no peer reviewed studies that have identified the presence of these four processes in children younger than 8-10 years and even in this age group occurrence is infrequent.

Development of sexual orientation 

Genetic, hormonal, and environmental factors contribute to sexual orientation, with genetic factors contributing approximately 33% of the variance. The most significant environmental influences occur intrauterine but there is continuing debate about what, if any, part is played by the postnatal familial and social environment.[11] 

Many of these factors overlap with those discussed as influential in gender development and will not be repeated here. Because of these commonalities, there is a strong relationship between gendered behaviour in children and sexual orientation in adulthood.[12] For example, a metanalysis of 28 studies (n~5,300) demonstrated a very close association between gendered behaviour in childhood (e.g., rough-and-tumble play, toy and activity preferences, role playing, cross-gender dressing, sex of peer group, appellations of “sissy” or “tomboy,” and stated gender identity) and sexual orientation in adulthood.[13] In boys, disinterest in rough-and-tumble play in childhood correlated with homosexual interest in adulthood.[14],[15]

A more recent study[16] has confirmed earlier findings of the link between childhood gender nonconforming (GNC) behaviour and later sexual orientation. The study comprising 2,428 girls and 2,169 boys from a population-based longitudinal study, the Avon Longitudinal Study of Parents and Children,[17] that followed children born in the 1990s for 15 years, found that the levels of GNC behaviour at ages 3.5 and 4.75 years accurately predicted adolescents’ perceived/stated sexual orientation at age 15 years. The authors argued that the factors contributing to the association between childhood GNC behaviour and sexual orientation may not be primarily socially determined, because children who develop into non-heterosexual adults appear to diverge from gender norms regardless of social encouragement to conform to gender roles. 

Biological factors

There is growing research support for a biological basis to sexual orientation.[18],[19] These include genetic influences, hormonal, and neurobiological factors. 

  • Genetic influences

Sibling studies show more concordance in sexual orientation between monozygotic (i.e., genetically identical, MZ) twins than between dizygotic (i.e., genetically non-identical twins, DZ) or other siblings.[20] A study of 4,900 twins identified a genetic basis for cross-gender behaviour in childhood and homosexual behaviour in adulthood. In male MZ twins, there was a moderate correlation for GNC behaviour in childhood (0.54) and sexual orientation in adulthood (0.51), compared with 0.11 and 0.14, respectively, for male DZ twins. Female MZ twins showed slightly lower associations than male DZ twins between GNC behaviour (0.49) and sexual orientation (0.42) while female DZ twins showed similar concordance for GNC behaviour in childhood (0.45) but no association for sexual orientation in adulthood (0.06).[21] Homosexual male siblings showed similar levels of GNC behaviour and both brothers were either feminine GNC or masculine, suggesting the existence of familial-genetic subtypes of male homosexuality.[22] A number of studies have also identified regions on various chromosomes with linkages to sexual orientation.[23],[24]

  • Hormonal factors

A relationship between prenatal levels of sex steroids and postnatal gender-typed behaviours has been frequently reported. High maternal levels of androgens during pregnancy have been associated with gender nonconformity and same-sex attraction in offspring.[25] It has been suggested that gay men have lower exposure to prenatal androgens than heterosexual men and lesbian women have higher exposure than heterosexual women.[26] Girls with congenital adrenal hyperplasia (CAH) are exposed to higher levels of androgens in utero. They tend to be masculinized in their play as children and are more likely to express bisexual or homosexual orientation in adolescence and young adulthood.[27]

  • Neurobiological factors

Sexually dimorphic toy preferences reflect basic neurobiological differences between boys and girls that precede social or cognitive influences.[28] These sex differences in children’s play commence before gender development and sexual orientation.[29] Nonhuman primates confirm sex differences in novel toy selection observed in young children.[30] In both monkeys and children, males are more rigid in their toy selections than females. Similarly, in maturity, women are more likely to be attracted to both women and men.[31] Further, their sexual attractions appear more context dependent than male sexual attractions.[32] It follows, therefore, that social environments and impacts may exert a greater influence on female compared with male sexual orientation. 

Social factors

Family and social environments

There is little clear evidence that psychosocial factors contribute in any significant way to sexual orientation.[33]However, family composition may affect the likelihood of homosexual orientation in male children.[34]  One of the most compelling findings supporting the influence of familial and social factors on the development of a homosexual orientation is the fraternal-birth-order effect (FBOE).[35] The effect is defined as the higher probability of homosexuality in males with (an) older biological brother(s). Older sisters, older adoptive brothers or stepbrothers do not confer the same effect. The effect pertains even if the older biological brothers grew up apart. The FOBE effect has been observed cross-culturally. The greater the number of older brothers, the greater the probability of homosexual orientation in the youngest brother. The origin of this effect is thought to be intrauterine whereby male-specific antigens on the Y chromosome trigger an immune response in the mother during a first pregnancy with a male foetus. Antibody levels rise with each subsequent male pregnancy, which has the effect of altering sexual differentiation. Recent research has demonstrated that mothers of gay sons have higher antibodies to neuroligin 4 (a Y-linked antigen) than mothers of heterosexual sons.[36] Equally, such a finding could be used to assert the role of hormonal factors in homosexuality since the determinative factor is hormonal occurring in utero but created by family constellation which alters the uterine environment for successive male foetuses. FBOE predicts gender nonconformity in homosexual men.[37]

Lesbian and gay parents may have a higher proportion of biologic lesbian or gay offspring as a result of shared genetic material.[38] Further, lesbian and gay adults, most of whom grew up in heterosexual households, report higher rates of childhood sexual victimization than their heterosexual peers.[39] However, a young person’s same-sex attraction could have preceded the abuse or young people who demonstrate same-sex attraction may be specifically targeted for abuse.[40]

Sexual orientation in women may be more affected by family and social environments compared with men. On average, women reported that they first became aware of their same-sex attractions at age 16 (SD = 8 years),[41] first disclosed their sexual orientation to another person at age 23 (SD = 8 years), and first had sex with another woman at 21 (SD = 7 years).[42] Note the wide standard deviations in each of these average age figures that demonstrate high variability in the timing of these events. Applying the standard deviation to these figures, the youngest age would be eight years. 

Sexual orientation in females appears more likely to change over time.[43] Hypotheses regarding the greater sexual orientation fluidity in females compared with males include biologically based sex differences in foetal hormone exposure and socio-political forces that constrain sexual self-concept, expression, and opportunities differently in women and men.[44] However, there are very few empirical studies with longitudinal data across the life course and across the different dimensions of sexual orientation that can further elucidate fluidity in female sexual orientation.[45]

[1] 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.

[2] Institute of Medicine. (1999). Lesbian health: Current assessment and directions for the future. Washington, DC: National Academy Press.

[3] Bogaert, A. F., & Skorska, M. N. (2020). A short review of biological research on the development of sexual orientation. Hormones and Behavior, 119, 104659.

[4] Perrin, E. C. (2002). Sexual orientation in child and adolescent health care. New York: Kluwer Academic/ Plenum Publishers.

[5] Herdt, G., & McClintock, M. (2000). The magical age of 10. Archives of Sexual Behaviour, 29, 587.

[6] Floyd, F. J., & Bakeman, R. (2006). Coming-out across the life course: Implications of age and historical context. Archives of Sexual Behaviour, 35, 287–296.

[7] Ganna, A., Verweij, K. J., Nivard, M. G., Maier, R., Wedow, R., Busch, A. S., … & Zietsch, B. P. (2019). Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior. Science, 365(6456), eaat7693.

[8] Savin-Williams, R. C., Cash, B. M., McCormack, M., & Rieger, G. (2017). Gay, mostly gay, or bisexual leaning gay? An exploratory study distinguishing gay sexual orientations among young men. Archives of Sexual Behavior46(1), 265-272.

[9] Cass V. (1996). Sexual orientation identity formation: A western phenomenon. In: Cabaj, R. P., & Stein, T. S. (1996). Textbook of homosexuality and mental health. American Psychiatric Association.

[10] Floyd, F. J., & Bakeman, R. (2006). Coming-out across the life course: Implications of age and historical context. Archives of Sexual Behaviour,35(3), 287-296.

[11] Christopher C. H. Cook (2021). The causes of human sexual orientation. Theology & Sexuality, 27, 1, 1-19, DOI: 10.1080/13558358.2020.1818541

[12] Bailey, J. and Zucker, K. (1995). Childhood sex-typed behaviour and sexual orientation: a conceptual analysis and quantitative review. Developmental Psychology, 31, 43-55.

[13] Bailey, J. and Zucker, K. (1995), Childhood sex-typed behaviour and sexual orientation: a conceptual analysis and quantitative review. Developmental Psychology 31:43-55.

[14] McConaghy, N., Buhrich, N. & Silove, D. (1994), Opposite sex-linked behaviour and homosexual feelings in the predominantly heterosexual male majority. Archives Sexual Behaviour, 23:565-577.

[15] Kenneth J. Zucker PhD. (2008) Reflections on the relation between sex-typed behavior in childhood and sexual orientation in adulthood. Journal of Gay & Lesbian Mental Health, 12,1 -2, 29-59.

[16] Li, G., Kung, K. T. F., & Hines, M. (2017). Childhood gender-typed behavior and adolescent sexual orientation: A longitudinal population-based study.  Developmental Psychology, 53(4), 764 -777.

[17] Golding, J., Pembrey, M., Jones, R., ALSPAC Study Team. ALSPAC–the Avon Longitudinal Study of Parents and Children. (2001). I. Study methodology. Paediatric and perinatal epidemiology. 15(1):74-87. DOI: 10.1046/j.1365-3016.2001.00325.x. Also, see

[18] 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 Interest17(2), 45-101.

[19] LeVay, S. (2016). Gay, straight, and the reason why: The science of sexual orientation. Oxford University Press.

[20] Langstrom, N., Rahman, Q., Carlstrom, E., & Lichtenstein, P. (2010). Genetic and environmental effects on same-sex sexual behaviour: A population study of twins in Sweden. Archives of Sexual Behaviour, 39, 75–80.

[21] Bailey, J., Pillard, R., Neale, M. & Agyei, Y. (1993). Heritable factors influence sexual orientation in women. Archives General Psychiatry, 50:217-223.

[22] Dawood, K., Pillard, R., Horvath, C., Revelle, W. & Bailey, J. (2000), Familial aspects of male homosexuality. Archives of Sexual Behaviour, 29:155-163.

[23] Mustanski, B. S., DuPree, M. G., Nievergelt, C. M., Bocklandt, S., Schork, N. J., & Hamer, D. H. (2005). A genomewide scan of male sexual orientation. Human Genetics, 116(4), 272-278.

[24] Sanders, A. R., Beecham, G. W., Guo, S., Dawood, K., Rieger, G., Badner, J. A., … & Martin, E. R. (2017). Genome-wide association study of male sexual orientation. Scientific Reports, 7(1), 1-6.

[25] Hines, M., Brook, C., & Conway, G. S. (2004). Androgen and psycho-sexual development: Core gender identity, sexual orientation and recalled childhood gender role behaviour in women and men with congenital adrenal hyperplasia (CAH). Journal of Sex Research, 41, 75–81.

[26] Breedlove, S. M. (2010). Minireview: organizational hypothesis: instances of the fingerpost. Endocrinology, 151(9), 4116-4122.

[27] Green, R. (2008). Childhood cross-gender behavior and adult homosexuality: Why the link? Journal of Gay & Lesbian Mental Health12(1-2), 17-28.

[28] Williams, C. L., & Pleil, K. E. (2008). Toy story: Why do monkey and human males prefer trucks? Comment on “Sex differences in rhesus monkey toy preferences parallel those of children” by Hassett, Siebert and Wallen. Hormones and Behavior, 54(3), 355-358. doi:

[29]. Berenbaum, S. A., Martin, C. L., Hanish, L. D., Briggs, P. T., & Fabes, R. A. (2008). Sex differences in children’s play. Sex differences in the brain:From genes to Behavior, 275, 290.

[30] Hassett, J. M., Siebert, E. R., & Wallen, K. (2008). Sex differences in rhesus monkey toy preferences parallel those of children. Hormones and Behavior, 54(3), 359-364. doi: 10.1016/j.yhbeh.2008.03.008

[31] Cook, C. C. (2021). The causes of human sexual orientation. Theology & Sexuality27(1), 1-19.

[32] Diamond, L.M. (2012). The desire disorder in research on sexual orientation in women: Contributions of dynamical systems theory. Archives of Sexual Behaviour, 41, 73–83 (2012).

[33] Xu, Y., Norton, S., & Rahman, Q. (2020). A longitudinal birth cohort study of early life conditions, psychosocial factors, and emerging adolescent sexual orientation. Developmental Psychobiology, 62(1), 5-20.

[34] Golombok, S. (2000). Parenting: What really counts? Philadelphia: Taylor & Francis.

[35] Blanchard, R. (2018). Fraternal birth order, family size, and male homosexuality: Meta-analysis of studies spanning 25 years. Archives of Sexual Behavior47(1), 1-15.

[36] Garretson, J., & Suhay, E. (2016). Scientific communication about biological influences on homosexuality and the politics of gay rights. Political Research Quarterly69(1), 17-29.

[37] Swift-Gallant, A., Coome, L. A., Aitken, M., Monks, D. A., & VanderLaan, D. P. (2019). Evidence for distinct biodevelopmental influences on male sexual orientation. Proceedings of the National Academy of Sciences116(26), 12787-12792.

[38] Goldberg, A. E. (2010). Lesbian and gay parents and their children: Research on the family life cycle. Washington, DC: American Psychological Association.

[39] Balsam, K. F., Levahot, K., Beadnell, B., & Circo, E. (2010). Childhood abuse and mental health indicators among ethnically diverse lesbian, gay, and bisexual adults. Journal of Consulting and Clinical Psychology, 78, 459–468.

[40] Wilson, H. W., & Widom, C. S. (2010). Does physical abuse, sexual abuse, or neglect in childhood increase the likelihood of same-sex sexual relationships and cohabition? A prospective 30-year follow-up. Archives of Sexual Behaviour, 39, 63–74.

[41] Standard deviation is a number used to tell how measurements for a group are spread out from the average (mean) or expected value. A low standard deviation means that most of the numbers are close to the average. A high standard deviation indicates greater dispersion or distance from the mean value.

[42] Corliss, H. L., Cochran, S. D., Mays, V. M., Greenland, S., & Seeman, T. E. (2009). Age of minority sexual orientation development and risk of childhood maltreatment and suicide attempts in women. The American Journal of Orthopsychiatry79(4), 511–521.

[43] Baumeister, R. F. (2000). Gender differences in erotic plasticity: The female sex drive as a socially flexible and responsive. Psychological Bulletin,126, 347–374.

[44] Diamond, L. M. (2007). A dynamical systems approach to the development and expression of female same-sex sexuality. Perspectives in Psychological Science, 2, 142–161.

[45] 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 Behaviour, 34, 173–183.