Do left-handed children have advantages regarding school performance and leadership skills?

A handedness polymorphism exists in all human populations so far investigated, at least since the Palaeolithic. Handedness is a heritable trait, and a possible evolutionary explanation for the higher prevalence of right-handers is the association of left-handedness with some deleterious traits. In this context, the persistence of left-handers remains unexplained. Reproductive success has been shown to be dependent on cultural success in many human societies. This study is the first attempt to consider the importance of social status to evolutionary processes related to handedness. We conducted a survey in French public primary schools to look for a possible association between laterality, school performance, and leadership skills. This study revealed only weak associations, and a sex effect. For primary-school girls, we report a negative association between several indicators of left-sidedness and teacher's ratings of school performance and leadership skills. For primary-school boys, we report a positive association between left-handedness for writing and teacher's ratings of school performance. The present study did not reveal any strong relation between laterality and school performance, but has shown that general school performance is not independent of laterality, and that the effect is opposite in males and females. The main difficulty is now to define clearly the different intellectual functions involved.