Digit ratio and laterality indices: the Chuvashian study

Abstract

The aim of the present study was to evaluate the association between digit ratio indices (representing the prenatal androgen and estrogen exposure) and different laterality indices, handedness (HDD), the dominant eye (DE), hand clasping (HCL) and arm folding (ARMF) in a large (N=1,586) Chuvashian population-based sample.HDD showed a significant association with the right phalangeal length ratio, the right and the left metacarpal ratio and the right ray ratio. Subjects with a right dominant hand had lower right phalangeal, right and left metacarpal and right ray ratios than those with a left dominant hand. This is the first study showing a significant association between the eye dominance and the left metacarpal and the left ray ratios. Subjects with a right DE had lower left metacarpal and left ray ratios than those with the left DE. HCL and ARMF showed no association with radiologically measured digit ratios. 2D:4D; digit ratio; laterality, handedness, dominant eye, hand clasping, arm folding, the Chuvashian population Laterality is the preference most humans show for one side of their body over the other. A majority of humans are right-handed and right-sided. According to Porac & Coren [30] approximately 88.2% favor their right hand and 71.1% Keywords:

An examination of the influence of prenatal sex hormones on handedness: Literature review and amniotic fluid data

“…It has been proposed that this indicates the level of exposure (and/or sensitivity) to prenatal testosterone (Brown et al, 2002;Manning et al, 1998;Ventura et al, 2013) or the ratio of prenatal testosterone to estradiol (Lutchmaya et al, 2004;Manning, 2011;Zheng and Cohn, 2011). Some studies have reported left-handedness to be associated with male-typical patterns of digit ratio (e.g., Beaton et al, 2011;Fink et al, 2004;Manning and Peters, 2009;Manning et al, 2000;Nicholls et al, 2008;Stoyanov et al, 2011;Stoyanov et al, 2009;Swami et al, 2013;Voracek et al, 2006), others with female-typical patterns (e. g., Baker et al, 2013;Gillam et al, 2008;Jackson, 2008;Kalichman et al, 2014;Ypsilanti et al, 2008), and yet others with no effect at all (e. g., Bescós et al, 2009;Boets et al, 2007;Papadatou-Pastou and Martin, 2017). A meta-analysis of published and unpublished literature (Richards et al, in press) reported negligible effect size estimates (all unsigned point estimates r < 0.060) that were not consistent in direction.…”