"The 2D:4D ratio is so variable, and the sex difference so small, that you can't determine someone's sex by knowing it. But it does tell you something about the extent of fetal testosterone exposure. So what does the extent of exposure (as assessed by the ratio) predict about adult behavior? Men with more "masculine" 2D:4D ratios tend toward higher levels of aggression and math scores; more assertive personalities; higher rates of ADHD and autism (diseases with strong male biases); and decreased risk of depression and anxiety (disorders with a female skew). The faces and handwriting of such men are judged to be more "masculine." Furthermore, some reports show a decreased likelihood of being gay. Women having a more "feminine" ratio have less chance of autism and more of anorexia (a female-biased disease). They're less likely to be left-handed (a male-skewed trait). Moreover, they exhibit less athletic ability and more attraction to highly masculine faces. And they're more likely to be straight or, if lesbian, more likely to take stereotypical female sexual roles.72"