From the article:
The new study has several important implications. First, that current levels of testosterone directly affect the ability to read someone else’s mind. This may help explain why on average women perform better on such tests than men, since men on average produce more testosterone than women.
Second, that the digit ratio (2D:4D), a marker of fetal testosterone, predicts the extent to which later testosterone has this effect. This suggests testosterone levels in the womb have an ‘organizing’ or long-range effect on later brain function. Finally, given that people with autism have difficulties in mind reading, and that autism affects males more often than females, the study provides further support for the androgen theory of autism.
From the publication:
Fetal testosterone is associated with a fixed somatic marker that can be indexed after birth: the length ratio of the right hand’s second (i.e., index) to fourth (i.e., ring) finger (2D:4D ratio). Males on average have a significantly lower 2D:4D ratio on their right hand and fetal testosterone is thought to underlie this sex difference, including its variability within the sexes. The reliability of 2D:4D ratio as a marker of fetal testosterone is substantiated by a large amount of correlational evidence in animals and humans. Moreover, meta-analytic data show that 2D:4D ratio is unaffected by later testosterone fluctuations or circulating levels of testosterone in adulthood. The ratio is therefore considered a useful, noninvasive marker of fetal testosterone.