Sex hormones and finger length What does 2D:4D indicate? David A. Putz a, *, Steven J. C. Gaulin b , Robert J. Sporter c , Donald H. McBurney c a Department of Anthropology, University of Pittsburgh, Pittsburgh, PA 15260, USA b Department of Anthropology, University of California, Santa Barbara, CA 93106, USA c Department of Psychology, University of Pittsburgh, Pittsburgh, PA 15260, USA Received 30 January 2004; accepted 26 March 2004 Abstract Much recent research has focused on the ratio of the lengths of the second to fourth manual digits (2D:4D) as a predictor of the degree of expression of sexually dimorphic and other sex-hormone- mediated traits. However, published findings are often contradictory or subject to various methodological problems. In the present study, we reassessed the relationships among three measures of 2D:4D (left hand, right hand, and mean) and several variables previously claimed to be related to 2D:4D, including sexual orientation, spatial ability, status, physical prowess, and components of reproductive success. In addition, we examined the relationship between 2D:4D measures and several other traits whose expression is thought to be related to sex hormones, including voice pitch, sociosexuality, mating success, and fluctuating asymmetry. 2D:4D measures showed highly significant sex differences, as did spatial ability, sociosexuality, components of reproductive and mating success, and fluctuating asymmetry. However, out of 57 correlations, 2D:4D correlated significantly in the predicted direction only with sexual orientation (for both sexes) and only for left hand 2D:4D. We discuss the recent 2D:4D literature in light of these findings and consider their implications for understanding the timing of developmental events. D 2004 Elsevier Inc. All rights reserved. Keywords: 2D:4D; 2D/4D; Androgens; Digit length; Digit ratio; Sex differences; Sex hormones; Testosterone 1090-5138/04/$ – see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.evolhumbehav.2004.03.005 * Corresponding author. Tel.: +1-412-648-7500. E-mail address: dapst49@pitt.edu (D.A. Putz). Evolution and Human Behavior 25 (2004) 182 – 199