[gus_massa]

All the subject if full of conflicting information. From Wikipedia: http://en.wikipedia.org/wiki/Digit_ratio

> Assuming a normal distribution, the 95% confidence interval for average length is 0.889-1.005 for males and 0.913-1.017 for females.

> In Manning's words, "There's more difference between a Pole and a Finn, than a man and a woman."

> 2D:4D is being used alongside other methods to help sex Palaeolithic hand stencils found in European and Indonesian caves.

[nerfhammer]

if digit ratio were meaningless, why could it happen to predict toy preference?

other hormone effects, congenital adrenal hyperplasia can also be detected with blood tests, as was the case e.g. http://www.ncbi.nlm.nih.gov/pubmed/12414881