Asymmetric interference in left-handers during bimanual movements reflects switch in lateralized control characteristics.

Interactions between the hands are a collateral of simultaneous bimanual movements and can inform us about the functional asymmetries of the dominant and nondominant hemisphere-effector systems. Few studies on bimanual coordination have focused on discrete movement control, and even fewer have looked at this in the context of handedness. Using a novel bimanual paradigm in which both hands perform simultaneous target-directed movements, this study addressed interference between the hands in two groups of left-handed individuals. In one group, the dominant hand was perturbed, and in the other, the nondominant hand; the respective contralateral hand moved without visual feedback. Results show that the kinematic perturbation of the dominant left hand resulted in directional interference in the nonvisible right hand. Similarly to previous studies using this bimanual paradigm, interference became manifest through isodirectional deviations in the nonvisible hand in the majority of participants. The findings mirror the results of a previous study in right-handers. At the same time, interference was overall weaker in the left-handers, and not as exclusively dominant to nondominant as in the previous right-handed sample. The results not only confirm that hand control characteristics switch with handedness, but also shape interactions between the hands accordingly in left-handers.