Mathematical ability and lateral asymmetry

The hypothesis that special ability in mathematics is associated with a reduction in bias to dextral preference and skill was examined in several samples of students and in 97 male and 27 female teachers of mathematics, mainly in Universities and Polytechnics. The math students and math teachers differed from controls, both general and academic, in the direction predicted and several comparisons were statistically significant. Differences were in most cases clearer for males than females. An analysis of the findings in relation to the right shift (RS) theory of handedness (Annett, 1972, 1978) suggests that the incidence of left preference and skill is slightly raised in mathematicians not because of any intrinsic advantage of left preference but rather because extreme bias to the right, as expected in those carrying a hypothesised rs++ genotype, is disadvantageous for mathematical thinking. If the role of mathematics can be regarded as one of developing languages to describe those aspects of human experience which otherwise could be understood only in visuo-spatial images, it can be seen to require a coordination of those aspects of human intelligence which have been distinguished as depending differentially on the left and right cerebral hemispheres. The present findings suggest that this process might be impeded by a double dose of a gene which promotes left hemisphere language specialisation.