Intersex, brain differences, and the transgender tipping point

Laverne Cox - Time cover
Over a decade ago, intersex and trans activist Raven Kaldera wrote that trans people seeking classification as intersex might be seeking legitimisation, as if a physical cause is necessary to obtain social or familial validation. He said that trans people using brain sex theories to claim intersex status were basing a political stance on unproven science and damaging the intersex community’s ability to organise.

We might hope that times have changed, with the amazing Laverne Cox appearing on the cover of Time magazine, as it declares The Transgender Tipping Point. This is great news (also, we can’t wait for the next series of Orange is the New Black) but, sadly, a high proportion of enquiries that we get at OII Australia, a national intersex organisation, are still from trans folk seeking biological validation for their identity.

Intersex is a term for innate physical differences in sex characteristics, known controversially to medicine as “Disorders of Sex Development” and historically as hermaphroditism. At least 30 or 40 genetic differences causing intersex traits are known to science. Intersex is not defined as a gender identity. Intersex people have all sorts of gender identities, just like trans and other people. Some intersex people have non-binary gender identities, just like some trans people, but most intersex people are men or women.

Correlations between brain sex differences and same sex attraction in men, and trans gender identities in women, have been widely reported over a long period of time – yet there’s still controversy even regarding the notion that men and women have different brains. Given the known biological basis of many intersex variations, much of the research on causes of homosexuality has been carried out on live foetuses and infants with intersex traits.

Late last year, a neuroscience study inspired headlines proclaiming, “hardwired difference between male and female brains could explain why men are “better at map reading” (And why women are “better at remembering a conversation”)”. Cordelia Fine writing at The Conversation shows how the reporting and the study itself, of nearly 1,000 people, inflated very modest differences into something “tediously predictable“. In reality:

In an larger earlier study … the same research team compellingly demonstrated that the sex differences in the psychological skills they measured – executive control, memory, reasoning, spatial processing, sensorimotor skills, and social cognition – are almost all trivially small…

the social phenomenon of gender means that a person’s biological sex has a significant impact on the experiences (including social, material, physical, and mental) she or he encounters which will, in turn, leave neurological traces.

The more research that is conducted, the more clear is the evidence that brains are plastic. Differences are often over-stated, especially where results fit social preconceptions, but brain structures change according to circumstance and repeated activities.

Studies in recent years have found that a short eight-week mindfulness meditation program changed the brain structures of 16 participants, while other studies have found brain differences in active longer-term meditators. Scientific American has collected some good links.

More recently, a study in Israel has found that parenting rewires the male brain, particularly those of gay men: “the experience of hands-on parenting, with no female mother anywhere in the picture, can configure a caregiver’s brain in the same way that pregnancy and childbirth do“. In heterosexual men, brain differences were “proportional to the amount of time they spent with the baby“.

Laverne Cox said in that Time interview (via The Guardian):

If someone needs to express their gender in a way that is different, that is OK, and they should not be denied healthcare. They should not be bullied. They don’t deserve to be victims of violence … That’s what people need to understand, that it’s okay and that if you are uncomfortable with it, then you need to look at yourself.

It’s time for a bit more pride, and time for phone calls seeking validation based on brain sex to stop.

Biological validation doesn’t improve access or quality of healthcare. Testing for biological differences creates its own risks. Basing a human rights campaign on being “born that way“, or not being able to help being different is undeniably seductive, but we all deserve human rights whether we’re born a particular way or not. It shouldn’t depend on your genetics or your brain structure any more than your gender expression or what you choose to wear.


  1. Raven Kaldera (c.2000-2004) Dangerous Intersections
  2. Katy Steinmetz (29 May 2014) The Transgender Tipping Point in Time Magazine
  3. Simon LeVay (30 August 1991) A difference in hypothalamic structure between heterosexual and homosexual men in Science 30 August 1991: Vol. 253 no. 5023 pp. 1034-1037. DOI: 10.1126/science.1887219
  4. OII Australia (29 April 2014) Submission on the ethics of genetic selection against intersex traits, includes material on research on the causes of homosexuality using foetuses and infants with intersex traits.
  5. Christie Nicholson (22 January 2011) Meditation Correlated with Structural Changes in the Brain in Scientific American
  6. Eileen Luders, Arthur W. Toga, Natasha Lepore and Christian Gaser (15 April 2009) The underlying anatomical correlates of long-term meditation: Larger hippocampal and frontal volumes of gray matter in Neuroimage, 15 April 2009; 45(3): 672–678. PMCID: PMC3184843, NIHMSID: NIHMS90659
  7. Scientific American (31 October 2013) Taking a Closer Look at How Meditation Improves Our Brains [Video], collected research on meditation and brain structure.
  8. Cordelia Fine (4 December 2013) New insights into gendered brain wiring, or a perfect case study in neurosexism? at The Conversation
  9. Elizabeth Norton (27 May 2014) Parenting Rewires the Male Brain, American Association for the Advancement of Science.
  10. Amanda Holpuch (30 May 2014) Laverne Cox heralds ‘transgender tipping point’ on cover of Time in The Guardian.

Also recommended:

More information

This page is not intended as an introduction to intersex. Introductory information, and reading on related issues: