Functional asymmetries in the quality of handwriting movements: a kinematic analysis.

Writing hand preference is a prominent functional asymmetry, but biomechanical factors may also contribute to any kinematic differences in the quality of handwriting movements performed by either hand. Eighteen dextral participants used a noninking pen with their right or left hand to write cursive letter ls, inverted ls, and their mirror images (to control for biomechanical differences) on a graphics tablet. Kinematic analysis of the scaling, consistency, efficiency, and shape of writing stroke trajectories revealed functional asymmetries between hands. The right hand was faster and produced more efficient strokes, which were of more consistent length, duration, and peak velocity. Differences between hands do not simply reflect biomechanical factors; therefore, the documentation of any functional asymmetries may allow their subsequent use as markers of underlying pathology in conditions such as schizophrenia.