That's actually pretty interesting. It sounds like what is going on here is finger ratio is a marker for testosterone/estrogen levels during development which in turn is predictive math/verbal abilities. What I wonder is, is it more predictive than, say, simply knowing the gender of the child?

To lamely reply to myself, it looks like it does: "Similarly, they found higher literacy SAT scores for the girls among those who had lower prenatal testosterone exposure, as indicated by a shorter ring finger compared with the index finger."