The effect of handedness on academic ability: a multivariate linear mixed model approach.

In recent years questions have arisen about whether there are any links between handedness and academic abilities as well as other factors. In this study we investigate the effects of gender, writing hand, relative hand skill, and UK region on mathematics and reading test scores by applying a multivariate linear mixed-effects model. A data sample based on 11,847 11-year-old pupils across the UK from the National Child Development Study was considered for the analysis. Our results show that pupils who write with one hand while having better skill with their other hand (i.e., inconsistent writing hand and superior hand) obtained lower test scores in both reading and mathematics than pupils with consistent writing hand and superior hand. Furthermore, we confirm previous findings that degree of relative hand skill has a significant effect on both reading and maths scores and that this association is not linear. We also found higher scores of reading in children from the south of England, and of mathematics in children from the south of England and Scotland, when compared to other UK regions.

Handedness in Great Britain.

Two large British databases of handedness assessed by writing hand at 10-11 years of age were analysed by geographical region. Left-handedness was found to vary significantly across regions according to one survey but not the other. In both data sets, left-handed writing was significantly more frequent in England than in Scotland and Wales combined. Possible reasons for this difference are discussed.

Lateralization of verbal ability in pre-psychotic children.

Deficits in lateralization have been reported in handedness, language and anatomical asymmetry in schizophrenia, but the relationship between these anomalies has been unclear. Extending earlier work demonstrating that degrees of lateralization are related to verbal ability in the general population, we here investigate the relationship in children who later developed psychosis. Using data from a box-marking test and an index of receptive verbal ability in the UK National Child Development study, we constructed three-dimensional plots of verbal ability in relation to left- and right-hand skill at the age of 11 years, and compared the performance of 34 children who by age 28 had developed schizophrenia and 21 who had developed affective psychosis with 12,782 in the total population. In the total population, verbal skill is decreased in those who are close to the L=R line. Children premorbid for schizophrenia are less lateralized and their verbal skill is lower than predicted by their hand skill, with a similar trend in children premorbid for affective psychosis. Thus pre-psychotic children deviate from the general population in the trajectory of lateralization of words. The findings are consistent with the concept that in psychosis at some critical stage in development there is a failure of lateralization of the components of language.

Word acquisition reflects lateralization of hand skill.

Right hand preference distinguishes Homo sapiens from our closest primate relative, the chimpanzee. Are differences in degrees of handedness associated with differences in the rate of language development? To answer this question, verbal performance is examined in relation to hand skill in a UK national birth cohort dataset. Using 3-D data plots, we show that increasing dominant-hand skill is associated with increasing verbal ability, and stronger lateralization is associated with earlier acquisition of words. Thus, right-handed bias is relevant to the lateralization of language; variation along this dimension may represent species-specific genetic or 'epigenetic' diversity.