PREDICTING READING-ABILITY FROM HANDEDNESS MEASURES

Word reading, hand skill on a peg-moving task and hand preference were measured in 203 children aged from 11-13 years. Differences in skill between the hands were largely attributable to variations in left-hand skill, consistent with the view that manual and cerebral asymmetry ar e due to the loss (pruning) of cells in the right hemisphere during de velopment-a mechanism that may be dependent on the 'right shift' (rs+) gene postulated by Annett (1985). There was only weak evidence for th e curvilinear relation between differential hand skill and reading pre dicted by Annett's (1985) theory of balanced polymorphism, which postu lates a heterozygotic advantage. Reading was better predicted by absol ute measures of hand skill than by the difference between the hands, e specially among boys. For the boys, word reading was predicted signifi cantly from right-hand skill, while for girls left-hand skill predicte d slightly more strongly than right-hand skill. This may be related to differential growth gradients in the two hemispheres, and different e nvironmental influences for boys and girls during a period of right he mispheric growth.