Individual differences in 2D:4D digit-ratios and otoacoustic emissions: Do they share a common developmental origin?

Differences across individuals in both 2D:4D, the ratio of the lengths of the 2nd-4th digit, and in otoacoustic emissions (OAEs), have been hypothesized to arise from differences in androgen exposure prenatally. Contrary to this hypothesis, however, McFadden and Shubel (2003) found no significant correlation between digit-ratios and OAE production. To further investigate the hypothesis of a common developmental origin, the current study assessed correlations between individual differences in 2D:4D and OAEs in 131 normally-hearing adults. All possible ratios of the 2nd, 3rd, 4th, and 5th digits were computed and OAEs, both spontaneously produced and in response to audible clicks, were measured. Observed correlations between digit length ratios and OAEs were largely nonsignificant. No significant correlations were found between 2D:4D and any of the five OAE measures. Fundamental differences in developmental timing and duration, postnatal influences, or factors other than prenatal androgens may explain the lack of associations.