Sexual orientation and the second to fourth finger length ratio: a meta-analysis in men and women.
Level 3 - non-randomized controlled study
Meta-analysis of observational/cross-sectional studies (graded by design analogy, not clinical CEBM)
PubMed 20364887 · doi:10.1037/a0018764
What was done
The authors performed a meta-analysis assessing the relationship between digit ratio (2D:4D) and sexual orientation across 18 independent male samples (1,618 heterosexual men, 1,503 gay men) and 16 independent female samples (1,693 heterosexual women, 1,014 lesbians), evaluating both hands and examining ethnicity as a moderator.
What was found
Heterosexual women had higher (more feminine) left- and right-hand 2D:4D than lesbians, whereas no difference was observed between heterosexual and gay men. Moderator analyses indicated that ethnicity accounted for some between-study variation in men. No numerical effect sizes, test statistics, or confidence intervals were reported in the abstract.
Why it matters
This adds evidence that prenatal sex hormone signaling may influence sexual orientation in women, while highlighting that the relationship in men is more complex and varies by ethnic background.
Limits
The abstract reports no numerical effect sizes or confidence intervals. Digit ratio is an indirect proxy for prenatal androgen exposure rather than a direct hormonal measurement, and substantial between-study variation was observed among men.
Cited by
- supports On average, lesbian women have more masculine 2D:4D digit ratios than heterosexual women, a finding confirmed across multiple meta-analyses.