Laterality, hand control and scholastic performance: a British birth cohort study

Objectives To use simple measures of laterality and hand control that can identify a greater risk of poorer scholastic ability, potentially signalling suboptimal hemispheric lateralisation. Design Analysis of material from a birth cohort study. Setting Members of the National Child Development Study, a British birth cohort study following people born in 1958. Participants 10？612 children who undertook tests at age 11？years. Primary outcome measures Teacher-administered tests of non-verbal general ability, verbal general ability, reading comprehension and mathematics. Results Linear regression produced associations (and 95% CIs) with tests of verbal general ability, non-verbal general ability, reading comprehension and mathematics scores for the lowest third (compared with highest) of a left-hand control test involving picking up matches of ？1.21 (？1.73 to ？0.68; p<0.001), ？0.72 (？1.14 to ？0.29; p=0.001), ？0.70 (？1.06 to ？0.35; p<0.001) and ？1.32 (？1.90 to ？0.73; p<0.001). Among those in the lowest third of the right-hand control test score, mixed-handedness compared with right-handedness was associated with poorer scholastic performance, with regression coefficients (and 95% CIs; p values) of 1.90 (？3.01 to ？0.80; p=0.001), ？1.25 (？2.15 to ？0.35; p=0.007), ？1.28 (2.04 to ？0.53; p=0.001) and ？1.33 (？2.53 to ？0.13; p=0.030). The estimates are for a point change in the scholastic test scores, after adjustment for sex, left-hand motor function and social class. Statistically significant associations with mixed-handedness were only observed for the lowest third of right-hand motor function. Conclusions Measures involving poorer left-hand motor function may represent useful markers of reduced cognitive function possibly reflecting suboptimal hemispheric lateralisation. Crude measures of laterality such as reported non-right-handedness may be more useful for research when combined with measures of motor function