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.