HANDEDNESS AND EDUCATIONAL SUCCESS - THE HYPOTHESIS OF A GENETIC BALANCED POLYMORPHISM WITH HETEROZYGOTE ADVANTAGE FOR LATERALITY AND ABILITY

A sample of children assessed for hand preference and hand skill at 14-15 years could be classified on two independent measures of educational success. One was whether they had been selected or not selected for grammar school two years earlier; the other was the performance of unselected children in the examinations of the General Certificate of Secondary Education (GCSE) some 18 months later. There were no differences for hand preference, but the successful children were significantly more often in the centre of the distribution of differences between the hands in skill than at the extremes, in both comparisons. The findings support the hypothesis prompted by the right shift theory of handedness (Annett, 1972, 1985) that there is natural variation for laterality and ability as expected for a genetic balanced polymorphism with heterozygote advantage. The findings cannot be attributed to slowness of the non-preferred hand at the extremes of the distribution, as might be predicted by an explanation in terms of developmental pathology.