Precisely wrong? The problems with the Jones and Martin genetic model of sex differences in handedness and language lateralisation.

John Maynard Keynes, the economist, ‘‘preferred to be vaguely right to being precisely wrong’’ (Bhatt, 2001). For the theory of Jones and Martin (2010), its strength, which is undoubtedly its precision, is also its weakness, for the theory allows precise calculations that undermine not only its application to sex differences in language lateralisation, but also its predecessor theory of sex differences in handedness (Jones and Martin, 2000). To my eye, and perhaps also the two other (anonymous) reviewers of the paper, Jones and Martin’s theory is precisely wrong. Having said that, science functions best in the public domain, rather than behind an editor’s closed doors, and others may disagree with my perceptions. In this commentary, I will briefly set out the theory, and then look at its problems, firstly in explaining handedness, and secondly in explaining language dominance. It should be noted in particular that if the model fails for handedness then it fails a fortiori for language dominance, since the model for language dominance is built upon that of handedness.