Why the preferred hand taps more quickly than the non-preferred hand: Three experiments on handedness.

Three separate experiments pursue the question of why the preferred hand outperforms the non-preferred hand on a simple finger tapping task. Experiment I rules out possible differential effects of fatigue on the differences between hands. Experiment 11 shows that the singledirection components of the 'up' and 'down' travel of the index finger are not significantly related to tapping speed and contribute little to the performance differences between hands. This is not so for the reversal portion of the tapping movement, where the transition between movement directions is made. This portion contributes significantly to the superiority of the preferred hand. It is suggested that sensory feedback plays a minor role and that the principal factor in the preferred hand's better performance is precision of force modulation. Manipulation of this factor (Experiment m) leads to changes in the magnitude of the preferred hand's superiority.