The digit ratio is the ratio of the lengths of different digits or fingers typically measured from the bottom crease where the finger joins the hand to the tip of the finger. It has been suggested by some scientists that the ratio of two digits in particular, the 2nd and 4th, is affected by exposure to androgens e.g. testosterone while in the uterus and that this 2D:4D ratio can be considered a crude measure for prenatal androgen exposure, with lower 2D:4D ratios pointing to higher androgen exposure.2D:4D is sexually dimorphic: in males, the second digit tends to be shorter than the fourth, and in females the second tends to be the same size or slightly longer than the fourth. This trait may be better considered 'sexually differentiated' rather than 'sexually dimorphic' in recognition of the fact that the effect size is fairly small, especially compared to other sexually dimorphic traits e.g. height.