John Money Gender Experiment: Reimer Twins

What Did John Money Do To The Twins

The Accident and Money’s Theory of Gender Neutrality

David Reimer was an identical twin boy, born in Canada in 1965. He was 8 months old at the time. A botched circumcision left his penis irreparably damaged.

John Money, a psychologist from Johns Hopkins University, had a prominent reputation in the field of sexual development and gender identity.

David’s parents took David to see Dr. Money at Johns Hopkins Hospital in Baltimore. He advised that David be “sex reassigned” as a girl through surgical, hormonal, and psychological treatments. Money had one answer: raise the child as a girl.

John Money believed that gender identity is primarily learned through one’s upbringing (nurture) as opposed to one’s inborn traits (nature). He argued this held only within a critical period of about two and a half to three years. That is why early reassignment mattered to his theory.

He proposed that gender identity could be changed through behavioral interventions. He advocated gender reassignment as treatment for any child with intersex traits or atypical sex anatomies.

Dr. John Money argued that it’s possible to habilitate a baby with a defective penis more effectively as a girl than a boy.

Reassignment and Growing Up as Brenda

At the age of 22 months, David underwent surgical castration to remove his testes, and surgeons constructed rudimentary female genitals from the existing tissue.

David’s parents raised him as a female and gave him the name Brenda (this name was chosen to be similar to his birth name, Bruce). David was given estrogen during adolescence to promote the development of breasts.

He was forced to wear dresses. He was also directed toward typical female norms, such as playing with dolls and mingling with other girls.

Throughout his childhood, David was never told that he was biologically male. He did not know the truth. He was part of a controversial investigation testing Money’s theory that nurture, not nature, determines gender identity and sexual orientation.

David’s twin brother, Brian, served as the ideal control because the brothers shared the same genes and the same prenatal hormones. Only their assigned rearing differed, which is what made any later difference between them so revealing.

One was raised a girl, the other a boy. Money continued to see David and Brian for consultations and checkups annually.

Money’s Sessions and the Reported “Success”

During these check-ups, Money would force the twins to rehearse sexual acts and inspect one another’s genitals. He sometimes photographed the twins during these sessions. Money claimed that childhood sexual rehearsal play was important for healthy childhood sexual exploration.

David also recalls receiving anger and verbal abuse from Money if they resisted participation.

Money (1972) reported on Reimer’s progress as the “John/Joan case” to keep the identity of David anonymous. Money described David’s transition as successful.

He claimed that David behaved like a little girl, with none of Brian’s boyish mannerisms.

Money published this data to reinforce his theory that gender identity is learned through upbringing. The story spread quickly.

Textbooks and the popular press repeated it through the 1970s as proof that nurture could override biology, and it shaped how doctors treated other infants with damaged genitals.

The Truth Emerges

In reality, though, David was never happy as a girl. He rejected his female identity and experienced severe gender dysphoria. He would complain to his parents and teachers that he felt like a boy and would refuse to wear dresses or play with dolls.

He was severely bullied at school. He also experienced suicidal depression throughout adolescence. His father told him the truth about his birth and sex of rearing when he was around 14. David immediately assumed a male gender identity, calling himself David.

David Reimer underwent treatments to reverse the assignment such as testosterone injections and surgeries to remove his breasts and reconstruct a penis.

David married a woman named Jane in his early twenties and became stepfather to her children.

Diamond and Sigmundson Expose the True Outcome

Dr. Milton Diamond was a sexologist and long-standing scientific critic of Money.

In the mid-1990s, he worked with psychiatrist Keith Sigmundson to establish the true outcome of Money’s case.

• Aim: To establish the reassignment’s true long-term outcome, and to draw out clinical implications for how infants are reassigned.
• Method: Diamond and Sigmundson located the adult patient behind the anonymous “John/Joan” reports, interviewed him, and reviewed his medical record against Money’s published claims.
• Results: The reassignment had failed. David had rejected the female role since childhood and reverted to living as a man years earlier, directly contradicting the published “success”.
• Conclusion: Sex of rearing does not simply override a strong biological predisposition. Diamond and Sigmundson concluded that clinicians should reconsider routine neonatal reassignment of genetic males with damaged genitalia, with caution and full disclosure.

David’s Later Life, Death, and the Case’s Impact

David continued to suffer from psychological trauma throughout adulthood due to Money’s experiments and his harrowing childhood experiences.

David endured unemployment and marital difficulties. His twin brother, Brian, died in 2002 following an overdose.

In 2004, at the age of thirty-eight, David Reimer died by suicide.

David’s story became widely known. It appeared in multiple books, magazine articles, and documentaries.

He brought attention to the complications of gender identity. He also questioned the ethics of reassigning infants and children.

Once the truth came to light, Money’s claim of success collapsed.

The case led to a decline in sex reassignment surgeries for genetic-male infants with inadequate genitalia. It also brought the malleability of gender and sex into question.

Current guidance reflects this shift. Clinicians now generally rear a 46,XY infant with functional testes as male, regardless of penis size. Modern practice favours deferring irreversible surgery, disclosing full medical history, and letting the individual guide decisions about their own body when old enough to choose.

Cohort Evidence Beyond the Single Case

Reimer’s case is a single story. A stronger test asks the same question in groups: what happens to genetic males with typical male prenatal hormone exposure who are raised as girls?

Researchers have studied this question in cohorts of patients assigned female for reasons unrelated to Reimer’s accident.

These children share his essential biology, 46,XY chromosomes and a male-typical prenatal hormone history, without his personal trauma. Agreement between their outcomes and his case is therefore telling.

The Cloacal Exstrophy Cohort

Reiner and Gearhart (2004) followed genetic males born with cloacal exstrophy, a severe pelvic malformation. It leaves typical male prenatal hormones but an inadequate or absent penis.

Most of the children had already been assigned female in infancy, exactly as Reimer was.

• Aim: To assess gender identity outcomes in genetic males with cloacal exstrophy, most assigned female at birth for the same reason as Reimer.
• Method: A longitudinal study followed all 16 genetic males in a cloacal-exstrophy clinic, aged 5 to 16. Fourteen had been assigned female at birth; two were raised male after their parents refused reassignment.
• Results: Eight of the 14 children raised female declared themselves male during the study, while the two raised male stayed male. All 16 showed moderate-to-marked male-typical interests, regardless of assignment.
• Conclusion: Routine female assignment of genetic males with severe phallic inadequacy produces unpredictable, often male, gender identification. The cohort turns Reimer’s single case into a replicated pattern.

A Review Across Similar Conditions

Meyer-Bahlburg (2005) reviewed published cases across the three conditions closest to Reimer’s own: penile agenesis, cloacal exstrophy, and penile ablation, the exact category Reimer fell into.

All three leave a 46,XY child with typical male prenatal hormones but genitals judged too inadequate to raise as a boy under the old approach.

Female-raised 46,XY patients showed a much higher rate of later switching to a male identity than comparison groups whose rearing matched their prenatal hormones. Outcomes still varied; some patients stayed female-identified.

Meyer-Bahlburg judged the pattern incompatible with prenatal androgens alone fully determining identity. That is evidence for a strong biological influence, not proof of biological destiny. Together, the two studies convert Reimer’s single case into a broader, quantifiable pattern.

Critical Evaluation: Ethics, Bias, and the Limits of a Single Case Study

The Reimer case is scientifically important, but several limitations affect how much weight it can bear.

• Grave Ethical Violations: Money performed the reassignment on a non-consenting infant and kept the truth from David for years. His follow-up sessions involved coercive practices that caused lasting distress.
• Confirmation Bias in Reporting: For two decades, Money’s optimistic self-reports went unchallenged and shaped clinical policy, while evidence of David’s distress and rejection of the role was omitted.
• Limited Generalisability: One case, involving extreme trauma and deception, cannot establish how often reassignment succeeds or fails, or how strong biology’s influence is in general.
• Nature and Nurture Were Confounded: The deception, traumatic clinical visits, and bullying were environmental stressors that may have added to David’s distress independently of any biological effect.
• Biology Does Not Explain Everything: It refutes the claim that rearing alone decides gender identity, but it does not show that biology alone decides it either.

Contemporary Research

Research since 2015 has moved this debate from a single case to pooled, quantitative evidence. The strongest designs, meta-analyses and systematic reviews of DSD cohorts, now carry the argument.

Gender Dysphoria Across DSD Conditions

Babu and Shah (2021) conducted a systematic review and meta-analysis of gender dysphoria in people with differences of sex development (DSD).

• Aim: To estimate how often gender dysphoria occurs in adolescents and adults with DSD, and to inform sex-of-rearing decisions.
• Method: A systematic search covering 2005 to 2020 found 20 studies, pooled using multi-level meta-analytic models. The studies covered several DSD conditions, comparing dysphoria rates between patients reared female and reared male.
• Results: Overall, about 15% of DSD patients reported gender dysphoria. Rates stayed low, around 4%, when female rearing matched a feminised biology, but reached roughly 53% when a prenatally androgenised 46,XY child reared female later virilised at puberty.
• Conclusion: Gender identity outcome depends on the condition and its biology. Female rearing works when it matches the prenatal hormonal history, and often fails when it opposes strong prenatal androgen exposure, exactly the Reimer pattern, now measured across cohorts.

Do Prenatal Androgens Shape Behaviour?

Kung, Louie, Spencer and Hines (2024) pooled 20 samples of children with classic congenital adrenal hyperplasia (CAH), a condition where genetic females are exposed to unusually high prenatal androgens.

Girls with CAH showed a strong shift toward male-typical play compared with unaffected girls. Boys with CAH barely differed from unaffected boys.

Because the comparison isolates hormone exposure within each sex, this is strong evidence that early androgens shape gender-related development.

Biology and Socialisation Together

As Hines (2020) explains, gender-related behaviour has two sources. Early testosterone exposure and postnatal upbringing work together, along with the child’s own growing understanding of gender.

Early testosterone consistently shapes gender-role behaviour, identity, and sexual orientation. Effects on skills like spatial ability are weaker and less consistent.

Roselli (2018) reaches a similar conclusion from neurobiology. Prenatal testosterone masculinises gender identity and sexual orientation, while its relative absence feminises them.

Genes and other factors still matter, so no single cause fully explains the outcome. This modern evidence does not overturn Reimer’s case. It sharpens it: prenatal androgens exert a major, replicable influence on gender identity that rearing struggles to override.

Sources

Babu, R., & Shah, U. (2021). Gender identity disorder (GID) in adolescents and adults with differences of sex development (DSD): A systematic review and meta-analysis. Journal of Pediatric Urology, 17(1), 39–47. https://doi.org/10.1016/j.jpurol.2020.11.017

Colapinto, J. (2000). As nature made him: The boy who was raised as a girl. HarperCollins.

Diamond, M., & Sigmundson, H. K. (1997). Sex reassignment at birth: Long-term review and clinical implications. Archives of Pediatrics & Adolescent Medicine, 151(3), 298–304. https://doi.org/10.1001/archpedi.1997.02170400084015

Hines, M. (2020). Human gender development. Neuroscience & Biobehavioral Reviews, 118, 89–96. https://doi.org/10.1016/j.neubiorev.2020.07.018

Kung, K. T. F., Louie, K., Spencer, D., & Hines, M. (2024). Prenatal androgen exposure and sex-typical play behaviour: A meta-analysis of classic congenital adrenal hyperplasia studies. Neuroscience & Biobehavioral Reviews, 159, 105616. https://doi.org/10.1016/j.neubiorev.2024.105616

Meyer-Bahlburg, H. F. L. (2005). Gender identity outcome in female-raised 46,XY persons with penile agenesis, cloacal exstrophy of the bladder, or penile ablation. Archives of Sexual Behavior, 34(4), 423–438. https://doi.org/10.1007/s10508-005-4342-9

Money, J., & Ehrhardt, A. A. (1972). Man & woman, boy & girl: The differentiation and dimorphism of gender identity from conception to maturity. Johns Hopkins University Press.

Money, J., & Tucker, P. (1975). Sexual signatures: On being a man or a woman.

Money, J. (1994). The concept of gender identity disorder in childhood and adolescence after 39 years. Journal of Sex & Marital Therapy, 20(3), 163–177. https://doi.org/10.1080/00926239408403428

Reiner, W. G., & Gearhart, J. P. (2004). Discordant sexual identity in some genetic males with cloacal exstrophy assigned to female sex at birth. New England Journal of Medicine, 350(4), 333–341. https://doi.org/10.1056/NEJMoa022236

Roselli, C. E. (2018). Neurobiology of gender identity and sexual orientation. Journal of Neuroendocrinology, 30(7), e12562. https://doi.org/10.1111/jne.12562