Handedness and cognitive ability: Using meta-analysis to make sense of the data.

The literature on the relationship between handedness and cognitive ability is riddled with studies using different conceptualizations of handedness (e.g., hand preference vs hand skill, direction vs degree, consistency vs inconsistency) and different conceptualizations of cognitive ability (intelligence vs distinct abilities), as well as different measurements thereof. Recently the literature was summarized by means of meta-analytic techniques. The findings show quite robustly that when handedness is assessed as hand preference and individuals are classified according to direction (i.e., as left-handers vs right-handers), no differences in cognitive ability emerge between handedness groups. However, other evidence points to the importance of assessing degree rather than direction of handedness and of employing hand skill rather than hand preference measures. A meta-analysis of such studies has not been possible to date, due to their scarcity. It is here suggested that degree of handedness and hand skill measures are employed in future studies exploring the possible relationship between handedness and cognitive ability so as to elaborate whether or not such a relationship exists and if so, what its characteristics are.