Development of Laterality and Bimanual Interference of Fine Motor Movements in Childhood and Adolescence

Drawing and handwriting are fine motor skills acquired during childhood. We analyzed the development of laterality by comparing the performance of the dominant with the nondominant hand and the effect of bimanual interference in kinematic hand movement parameters (speed, automation, variability, and pressure). Healthy subjects (n = 187, 6–18 years) performed drawing tasks with both hands on a digitizing tablet followed by performance in the presence of an interfering task of the nondominant hand. Age correlated positively with speed, automation, and pressure, and negatively with variability for both hands. As task complexity increased, differences between both hands were less pronounced. Playing an instrument had a positive effect on the nondominant hand. Speed and automation showed a strong association with lateralization. Bimanual interference was associated with an increase of speed and variability. Maturation of hand laterality and the extent of bimanual interference in fine motor tasks are age-dependent processes.

Limitations on Coupling of Bimanual Movements Caused by Arm Dominance: When the Muscle Homology Principle Fails

Studies of bimanual movements typically report interference between motions of the two arms and preference to perform mirror-symmetrical patterns. However, recent studies have demonstrated that the two arms differ in the ability to control interaction torque (INT). This predicts limitations in the capability to perform mirror-symmetrical movements. Here, two experiments were performed to test this prediction. The first experiment included bimanual symmetrical and asymmetrical circle drawing at two frequency levels. Unimanual circle drawing was also recorded. The increases in cycling frequency caused differences between the two arms in movement trajectories in both bimanual modes, although the differences were more pronounced in the asymmetrical compared with the symmetrical mode. Based on torque analysis, the differences were attributed to the nondominant arm's decreased capability to control INT. The intraarm differences during the symmetrical pattern of bimanual movements were similar (although more pronounced) to those during unimanual movements. This finding was verified in the second experiment for symmetrical bimanual oval drawing. Four oval orientations were used to provide variations in INT. Similar to the first experiment, increases in cycling frequency caused spontaneous deviations from perfect bimanual symmetry associated with inefficient INT control in the nondominant arm. This finding supports the limitations in performing mirror-symmetrical bimanual movements due to differences in joint control between the arms. Based on our results and previous research, we argue that bimanual interference occurs during specification of characteristics of required motion, whereas lower-level generation of muscle forces is independent between the arms. A hierarchical model of bimanual control is proposed.