The digit ratio (2D:4D) in China: A meta-analysis.

OBJECTIVES

To explore the 2D:4D in China (mainland and Taiwan) and to analyze the influences of ethnicity, digit measurement methods, age, and latitude on Chinese 2D:4D.

METHODS

We here conducted a meta-analysis of the results of 28 studies. A total of 112 independent samples and 19,093 participants were included.

RESULTS

The sex difference in left 2D:4D only approached significance when outliers were removed (P = 0.078), whereas the right 2D:4D was significantly lower in males compared to females, showing that the magnitude of sex difference was greater for the right hand than for the left hand. No significant differences were found in the 2D:4D between Han and ethnic minorities. The 2D:4D of samples measured using indirect digit measurement tended to be lower than in samples measured using direct digit measurement. Moreover, there were no effects of age and latitude on the 2D:4D in China.

CONCLUSIONS

We concluded that the sex differences in Chinese 2D:4D are consistent with the results from western studies, and that genetic pool differences rather than latitude-related environmental variables affect the 2D:4D in China. In addition, 2D:4D measurements obtained by different digit measurement techniques should not be combined within one study, or used together in comparative studies.