Is Intraindividual Variability Different between Unimanual and Bimanual Speed-Accuracy Movements?

Dominant (right) and nondominant (left) hand differences in motor performance variables were investigated during targeted rapid aiming unimanual and bimanual (to two separate targets) speed-accuracy tasks. The performance of the dominant and nondominant hands were compared during rapid targeted unimanual and bimanual reaching tasks (50 repetitions) in adult, neurologically intact, right-handed men (n = 20). As task difficulty increased from unimanual to bimanual tasks, reaction time increased and velocity (average and maximal) of performance decreased significantly. The effect of hand was significant only on average movement velocity and on intraindividual variability of accuracy (in both cases performance in the left hand was worse). Variability of movement path (accuracy) was less in the right hand during both unimanual and bimanual tasks.