Gabe Mirkin, M.D.
A partial answer may come from a study in Biological
Psychology, showing that the ratio of a man's
second finger to his fourth finger appears to predict aggression.
The amount of testosterone a baby is exposed to in his mother’s
uterus determines how long his fourth finger grows. So men who
have been exposed to high levels of testosterone in utero have a
larger ratio of the fourth (“ring”) finger to the second (“index”)
finger and therefore are more prone to physical aggression later
in life.
The author of this study states: “This study shows that
events in the womb have subtle effects on children's personality."
Previous studies have shown that men with higher ratios of the
fourth to second finger may be better in sports and are usually
more dominant and masculine. On the other hand, these men
are at higher risk for autism and immune deficiency. Men have
larger finger ratios than women. The authors cautioned that
these findings link a larger finger ratio to "a tendency toward
physical aggression". They do not show that all men with larger
ratios are more aggressive.
Biological Psychology, March 2005
August 7, 2005