Finger Length Ratio (2D:4D) in Left- and Right-Handed Males

Abstract

The finger length ratio (2D:4D) is a biomarker for the prenatal levels of testosterone. The prenatal effects of testosterone on the development of brain hemispheres are considered as a key factor in the etiology of left-handedness. We tested whether 2D:4D correlates with the type of handedness in males (18 right-handers and 18 left-handers). Right hand 2D:4D, left hand 2D:4D, average 2D:4D, and the difference between right and left 2D:4D (D_r–l) were compared. The value of D_r–l in left-handers was significantly lower than D_r–l in right-handers. This result can be interpreted as proof that left-handers were subjected to higher levels of testosterone in utero.

Keywords:

• finger length ratio (2D:4D)
• handedness
• left- and right-handers
• testosterone