A now widely studied putative marker for prenatal sex hormones exposure or, more precisely, for the relative exposure to testosterone compared to estrogens while in uterus, is the second-to-fourth digit ratio (2D:4D), that is the ratio between the index (2D) and the ring (4D) fingers (e.g. Auger et al., 2013; Baron-Cohen et al. 2004; Baron-Cohen et al. 2005; Manning et al., 1998; Manning et al., 2013; Zheng & Cohn, 2011).

Earlier studies that have stood the test of replication have reported that 2D:4D varies by sex and ethnicity but that male 2D:4D tends to be lower than female 2D:4D in all ethnic groups and the effect is strongest in the right hand (Manning, 2002). These differences emerge prenatally and appear to be stable during the developing years (e.g. Manning, 2002; McIntyre et al., 2005; Trivers et al., 2006).The 2D:4D literature is large.

While a number of failed replications have been reported, 2D:4D appears to be successfully associated with cognitive abilities (Brañas-Garza & Rustichini, 2011); impulsivity (Hanoch et al., 2012); aggression (Bailey & Hurd, 2005; Coyne et al., 2007; Hampson et al., 2008) and risk-taking (Brañas-Garza & Rustichini, 2011; Coates et al., 2009; Garbarino et al., 2011; Sapienza et al., 2009; Stenstrom et al., 2011), among other effects on personality and cognition.

Notes: a) Full list of references here; b) There is very recent special issue on 2D:4D in PAID edited by Martin Voracek; c) You will find along these pages some basic ideas (and references) about the effect of 2D:4D on decision making. Deliberately my selection is focused on those papers (and authors) closer to economics than to pure decision making. Hopefully you would find it useful.