Writing hand preference and cognitive function across the childhood years: Findings from the Millennium Cohort Study

Some evidence suggests that non-right-handed children have somewhat lower cognitive abilities than their right-handed counterparts, but differences are weak and inconsistent. Further research is needed to understand whether cognitive skill differences between right-handed and non-right-handed children in the general population exist, and if so when they emerge, how they develop across time, and how they may vary for different skills. This study, using longitudinal data from 11,371 children (50.07 % girls) of the UK's Millennium Cohort Study (MCS), explored the associations between writing hand preference and a range of verbal and non-verbal cognitive skills (10 cognitive skill scores overall) at ages 3, 5, 7, and 11 years. Writing hand preference (right-hand/non-right-hand) was reported by children at age 14 (a retrospective measure). We imputed missing data and ran regression modelling, while adjusting for covariates. Writing hand preference was associated with pattern construction at ages 5 and 7 and with verbal reasoning and spatial working memory at age 11, with right-handers performing better. Effect sizes were very small. Sensitivity analyses excluding the small number of children reporting using either hand replicated these results. Our findings suggest that non-right-handed children show some disadvantage, especially in spatial skills, across the primary school years. Supporting their spatial skills could be of benefit.