Findings of development of gender and sexuality research project
Why I did the study.
The aim of the study was to biological and psychosocial (learning and social environment) factors that are related to the development of gender-variant or gender-typical identities.
It had previously been suggested that these factors are different in birth-assigned males with different sexual orientations.
Previous research has found evidence that genetics, hormone exposure prenatally (exposure while in parent’s womb), differences in the structure of part of the brain called the hypothalamus, being right handed versus left handed, number of older brothers, and abuse experiences are related to gender identity.
While a number of studies in the past have looked at these factors individually, this is the first known study to have examined the inter-relationships of these factors in one sample. Also, most of these previous studies only used specific types of people with gender-variant identities (such as transsexuals at a medical clinic, or members of a cross-dresser club). This was the first study of its type to include participants with a wide range of gender identities.
How I did the study.
A total of 2,277 people did the online questionnaire. This included people with gender-variant and gender-typical identities. Participants were mainly white/caucasian (92%) adults living in the USA (54%) and New Zealand (19%).
What I found.
Compared with people with gender-typical identities, people with gender-variant identities were more likely to report having a family member with a gender-variant identity. This finding, and a pooled analysis of case reports of twins with gender-variant identities indicated genes play a role in determining of gender identities.
Finger-length ratio, tendency towards systemising, and a systematic review of case-reports of gender identity outcomes for adults with intersex and related conditions, all indicated prenatal hormone determinants of gender identities.
Further evidence for biological factors came from elevated levels of non-right handedness among birth-assigned females with gender-variant identities.
While there was a relationship between abuse experience and degree of adult gender-variance, it was unclear whether this abuse experience was a cause or effect of gender identity development.
Contrary to past theorising, there were no differences in biological and psychosocial factors between birth-assigned male participants of different sexual orientations.
This was the first research to find evidence that biological and psychosocial factors are the same for transsexuals as for persons with other gender-variant identities.
Overall, these findings add support for a biological predisposition for gender-variant and gender-typical identities. Learning and social environment factors are likely to be complex and work in interaction with biological factors.