Thresholds of the R-L continuum measured from themean of RS - -, showing the expected incidences of left-handed males and females, twin and singleton. Mean shifts are 1.0z, 2.0z for singleborn males, 1.2z, 2.4z for singleborn females, 0.67z, 1.33z for twin males, and 0.8z, 1.6z for twin females, for the RS + - and RS + + genotypes respectively

DOI link for Thresholds of the R-L continuum measured from themean of RS - -, showing the expected incidences of left-handed males and females, twin and singleton. Mean shifts are 1.0z, 2.0z for singleborn males, 1.2z, 2.4z for singleborn females, 0.67z, 1.33z for twin males, and 0.8z, 1.6z for twin females, for the RS + - and RS + + genotypes respectively

Thresholds of the R-L continuum measured from themean of RS - -, showing the expected incidences of left-handed males and females, twin and singleton. Mean shifts are 1.0z, 2.0z for singleborn males, 1.2z, 2.4z for singleborn females, 0.67z, 1.33z for twin males, and 0.8z, 1.6z for twin females, for the RS + - and RS + + genotypes respectively