Laterality indices in the Chuvashian population.

The aim of the present study was to describe the frequencies of right or left dominance in handedness (HDD), dominant eye (DE), hand clasping (HCL) and arm folding (ARMF) and their combination in the Chuvashian population. We also evaluated the familial correlation and heritability of aforementioned traits in the studied population. The investigated cohort comprised 235 nuclear Chuvashian (Russia) families and included 595 men aged 18-89 years (mean 46.9) and 592 women aged 18-90 years (mean 48.5). Our study shows that in the Chuvashian population right handedness, right dominant eye, right hand clasping and left arm folding is a most frequent pattern. In the studied population 9.08% of males and 9.98% of females were left-handed. Left DE was observed in 22.84% of males and 21.81% of females. Left dominance in HCL was found in 47.63% of males and 49.32% of females, while left dominance in ARMF was in 52.02% of males and 58.98% of females. The frequencies of dominance in HDD, DE and HCL showed no statistically significant differences between the sexes, but we found a significant sex difference in ARMF (p = 0.016). Statistically significant correlations were found between dominances of HDD and HCL, HDD and DE, and HCL and DE. No confirmation of heritability was obtained concerning the DE, HCL or ARMF indices. However, we obtained a high heritability estimate for HDD (h2 = 0.19) that was based on statistically significant parent-offspring and sib-sib correlations.