Cognitive benefits of right-handedness: a meta-analysis.

Hand preference - which is related to cerebral dominance - is thought to be associated with cognitive skills; however, findings on this association are inconsistent and there is no consensus whether left- or right-handers have an advantage in either spatial or verbal abilities. In addition, it is not clear whether an interaction between sex and hand preference exists in relation to these cognitive abilities. As these matters are relevant from a neurodevelopmental perspective we performed a meta-analysis of the available literature. We searched PubMed and Embase, and included 14 studies (359,890 subjects) in the verbal ability meta-analysis and 16 studies (218,351 subjects) in the spatial ability meta-analysis. There was no difference between the full sample of left and right-handers for verbal ability, nor was there a hand preference-by-sex interaction. Subgroup analysis of children showed a small right-hand benefit. Our results further revealed a modest but significant effect favouring right-handedness for overall spatial ability, which was more pronounced when analysis was restricted to studies applying the mental rotation test. We could not identify a specific interaction with sex. Our results indicate that there is a small but significant cognitive advantage of right-handedness on spatial ability. In the verbal domain, this advantage is only significant in children. An interaction effect with sex is not confirmed.