Handedness and eye-dominance: a meta-analysis of their relationship.

About one in ten people is left-handed and one in three is left-eyed. The extent of the association of handedness and eyedness is unclear, as some eyedness measures are potentially contaminated by measures of handedness. A meta-analysis of hand-eye concordance in 54,087 subjects from 54 populations, found that concordance was 2.69 x greater in questionnaire rather than performance studies, 1.95 x greater in studies using unimanual monocular performance measures, and 6.29 x greater in studies using non-sighting measures of eye-dominance. In the remaining studies, which seemed to show no evidence of bias, the odds-ratio for hand-eye concordance was 2.53 x; in a population with 9.25% left-handedness and 36.53% left-eyedness, 34.43% of right-handers and 57.14% of left-handers are left-eyed. This pattern of hand-eye association poses problems for genetic models of cerebral lateralisation, which must invoke pleiotropic alleles at a single locus or epistatic interactions between multiple loci. There was no evidence that the incidence of eyedness, or the association between eyedness and handedness, differed between the sexes.