Second to fourth digit length ratio (2D:4D) and adult sex hormone levels:: New data and a meta-analytic review

The relative Length of the second (index) to the fourth (ring) finger (2D:4D) is a putative negative correlate of prenatal testosterone (T) exposure. Therefore, 2D:4D (and to a Lesser extent Dr-l, the difference between 2DAD in the right hand and in the left hand) has often been used to study effects of prenatal androgenization on human behavior and cognition. However, evidence suggests that 2D:4D may also be related to levels of circulating sex hormones in adults. This would question the validity of 2DAD as a means of studying the effects of prenatal sex hormones. Here we present new data from two non-chnical samples (64 women and 102 men) regarding the relationships of 2D:4D and Dr-l with circulating sex hormone Levels. We then present a meta-analytic review of all the present evidence regarding this issue. The results suggest that, in the normal population, 2DAD and Dr-l are not associated with adult sex hormone levels. The findings from this current study add to the growing body of evidence demonstrating that 2DAD is a suitable tool. to study the effects of prenatal androgenization on human behavior and cognition. (C) 2007 Elsevier Ltd. All rights reserved.