Eva-Maria Reuter, Ross Cunnington, Jason B Mattingley, Stephan Riek, Timothy J Carroll

There are well-documented differences in the way that people typically perform identical motor tasks with their dominant and the non-dominant arms. According Yadav and Sainburg's (2011) hybrid-control model, this is because the two arms rely to different degrees on impedance control versus predictive control processes. Here we assessed whether differences in limb control mechanisms influence the rate of feedforward compensation to a novel dynamic environment. Seventy-five healthy, right-handed participants, divided into four subsamples depending on the arm (left, right) and direction of the force field (ipsilateral, contralateral), reached to central targets in velocity-dependent curl force-fields. We assessed the rate at which participants developed predictive compensation for the force field using intermittent error clamp trials, and assessed both kinematic errors and initial aiming angles in the field trials. Participants who were exposed to fields that pushed the limb towards ipsilateral space reduced kinematic errors more slowly, built up less predictive field compensation, and relied more on strategic re-aiming than those exposed to contralateral fields. However, there were no significant differences in predictive field compensation or kinematic errors between limbs, suggesting that participants using either the left or the right arm could adapt equally well to novel dynamics. It therefore appears that the distinct preferences in control mechanisms typically observed for the dominant and non-dominant arms reflect a default mode that is based on habitual functional requirements, rather than an absolute limit in capacity to access the controller specialised for the opposite limb.