Sex and ethnic differences in 2nd to 4th digit ratio of children.
Level 4 - case-series / case-control
Cross-sectional observational population survey
PubMed 15500996 · doi:10.1016/j.earlhumdev.2004.06.004
What was done
A cross-sectional population survey examined the ratio between the second and fourth digit lengths (2D:4D) using photocopies of the right hand. The study evaluated 798 children across four ethnic groups: Moroccan Berbers (n = 90), Uygurs (n = 438) and Han (n = 118) from Northwest China, and Jamaicans (n = 152). Investigators analyzed variations in 2D:4D across sex and ethnicity, as well as associations with age and height.
What was found
The 2D:4D ratio was significantly lower in males than in females across the total sample (n = 798) and within the Uygur, Han, and Jamaican subgroups individually (specific numerical means and p-values were not reported in the abstract). Significant ethnic differences were identified: Han children had the highest mean 2D:4D, followed by Berbers and Uygurs, while Jamaican children had the lowest mean ratio. Sex and ethnic differences operated independently with no significant interaction effect. No associations were found between 2D:4D and age or height in the total sample.
Why it matters
The findings indicate that sex and ethnic differences in 2D:4D ratios are established in childhood and remain stable relative to age and height, mirroring patterns reported in adult populations.
Limits
The abstract reports no exact numerical values, effect sizes, or confidence intervals. Digit measurements were limited to photocopies of the right hand only, excluding left-hand measurements. Sample sizes were unbalanced across ethnic cohorts (ranging from 90 to 438), and the cross-sectional design cannot track individual longitudinal digit development.
Cited by
- supports The ratio of the second digit to the fourth digit (2D:4D) tends to be smaller in men than in women, and this sex difference is present in children.