A large sample

The following table reports the distribution of 2D:4D in our sample accounting for 1011 Caucasian adults (574 females, 18 ≤ age ≤ 25). The population has been sampled from students at the University of Granada, Spain. Both hands of all participants were scanned using a high-resolution scanner (Canon Slide 90) and their fingers were measured from the basal crease to the tip of the finger using Photoshop (see here for more details about the measurement). The results are displayed separately for males and females and for right and left hands (see Figures S1 and S2).The Skewness-Kurtosis. All Normality test suggests significant departures from normality of the distributions of men’s (but not women’s) 2D:4D at 5% level (pright,men=0.051, pright,women=0.460, pleft,men=0.028, pleft,women=0.089). The Q-Q plots and the Skewness coefficient reveal that the differences with normal distributions are due to the lowest and highest values of 2D:4D in the sample (Figure S2) and due to the asymmetry of the reported distributions, respectively. The average right hand 2D:4Ds and their standard errors (see the table) suggest that the true population means lie (with 95% probability) between 0.954-0.961 and 0.966-0.972 for males and females, respectively. For left hands, the true population means lie between 0.959-0.966 for men and 0.967-0.973 for women. Women have larger 2D:4Ds than men in all cases (p=0.000 in all cases). Numbers below 0.918 (bottom 10%) and above 1.001 (top 90%) are rare in men, while 80% of female 2D:4Ds lie between 0.926 and 1.011.Concerning the symmetry of right and left hands, if we disregard gender, the mean comparison test with paired data reveals that the mean right hand 2D:4D (0.964) is significantly smaller (p=0.001) than the mean on left hands (0.967). The correlation between both measures is 0.656, high but far from 1. However, this difference is mainly related to the asymmetry of men’s right and left hand 2D:4D. Their right hand 2D:4D (Mean: 0.957) is significantly smaller (p=0.000) than the mean left hand one (Mean: 0.963) even though the correlation is still highly significant (p=0.000). In contrast, the average right hand 2D:4D of women is statistically indistinguishable from the left hand one (Right Mean: 0.969; Left Mean: 0.970; p=0.348), but the correlation is still high (0.635; p=0.000).

Acknowledgements to Antonio Espín (Globe: Granada), Filipos Exadaktylos (ISPRA, Eur. Com.), Tere García (Globe: Granada) and Levent Neyse (Kiel Univ.) who helped a lot in data gathering and analysis.