Hand movements which cross the body midline: findings relating age differences to handedness.

Performance of 200 children (5 groups, 4 to 12 yr.) in an experimental study of spatial development was analyzed in terms of hand preference and differences in laterality of response. In accord with the literature a cross-lateral inhibition effect was confirmed but there were marked differences between hands. The supposed 'body midline' seemed to offer more resistance to one hand than to the other. Alternative explanations are suggested.