In the womb, a fetus with XY chromosomes is exposed to testosterone and other androgens that help it develop into a male. Research has shown that people exhibit features that give away how much testosterone we were exposed to before birth. The digit ratio is the ratio between the length of the second and fourth fingers. If both fingers are the same length, the ratio is 1. The lower the digit ratio (ring finger longer than index finger), the more testosterone the fetus was likely exposed to.
It is not clear why testosterone affects the length of your fingers, but there is significant evidence to support the theory. Men with a lower digit ratio tend to be described as more aggressive, dominant and overall “masculine”. Men with a higher digit ratio, closer to 1, are typically described to have more feminine traits such as higher emotional quotient, sensitivity and interestingly, excelling in mathematics and science. The effect is more pronounced in men but also affects women. Women with a low digit ratio are more likely to be assertive. It has also been shown that lesbian women have a lower digit ratio than heterosexual women.