Life-span age trends in laterality.

Laterality of hand, foot, eye, and ear was measured in a sample of 1964 subjects, ranging in age from 8 to 100 years. Age trends were found, with hand, foot, and eye preference becoming more right-sided and ear preference becoming more left-sided with increasing age. Sex differences emerged in foot, eye, and ear preference but these did not systematically interact with the age variable. Several causal mechanisms are proposed but none can fully explain either the direction or the magnitude of the observed age changes. Thus, these data are most consistent with the view that the study of sidedness in humans should proceed with a consideration of a complex of underlying factors and individual difference variables.