Previous studies have suggested that the left and right hands have different internal models for motor control. Thus, rather than one hand being superior to the other, each might have different specialties. If so, bimanual movements might be more accurately controlled because of the coordination of the two internal models. To investigate this possibility, we examined motor movement accuracy, reaction time, and movement time in pure right-handed subjects during a three-dimensional motor control task (visually guided reaching) under conditions of visual feedback and no visual feedback. In the no-visual-feedback condition, right-hand movement had lower accuracy and shorter reaction time than did left-hand movement, whereas bimanual movement had the longest reaction time, but the best accuracy. This suggests that the two hands have different internal models and specialties: closed-loop control for the right hand and open-loop control for the left hand. Thus, during bimanual movements, both models might be used, creating better control and planning (or prediction), but requiring more computation time compared to the use of only one hand.
