A reanalysis of five studies on sexual orientation and the relative length of the 2nd and 4th fingers (the 2D:4D ratio).

Five studies have examined the relationship between sexual orientation and the relative lengths of the 2nd and 4th fingers (the 2D:4D ratio). Although differences have commonly been found between heterosexuals and homosexuals, the direction of the difference has not been consistent across studies. The original data from all five studies were reanalyzed in a search for possible explanations of the discrepancies. Because ethnicity is known to affect the 2D:4D ratio, the reanalysis focused on participants who identified themselves as White or Caucasian, the ethnic group that was most numerous in all of the studies. Age differences did not account for the discrepancies. Differences in variability within different groups were minor. One interesting result to emerge from the reanalysis was that the 2D:4D ratios for the homosexual groups were relatively similar across studies. It was the 2D:4D values for the heterosexual participants that varied most, particularly between the USA and the British studies, and these were responsible for many of the discrepancies in the conclusions across studies. The constancy of the 2D:4D ratio for the White homosexuals did not appear to extend to homosexuals of three other ethnicities, and there were also subpopulation differences related to right or left hands.