Digit ratio
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The term digit ratio is used for the ratio of the lengths of the second and fourth digits of the human hand (the index and ring fingers). In males, the second digit tends to be shorter than the fourth, and in females the second tends to be longer. The effect size is fairly small, especially as compared to other sexually dimorphic traits such as height.
There is evidence that this reflects fetal exposure to the hormones testosterone and estrogen. Some authors go further, suggesting that this is correlated to health and behavior (including sexuality) in later life.
External links
- Hormones & Behaviour. Workshop 4: Homosexuality. (http://psych.unn.ac.uk/users/nick/HBppws04/tsld010.htm)
- Book review - Digit Ratio: A Pointer to Fertility, Behavior and Health (http://human-nature.com/nibbs/02/manning.html)
- abstract of The 2nd to 4th digit ratio and autism. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11263685&dopt=Abstract)
- Digit ratio and human evolution (http://www.digitratio.com)Template:Anatomy-stub