Discussion
Handedness
We explored control and adaptation strategies to investigate differences linked to hand dominance. We found that participants adapted their behavior in the presence of a force field (experiment 1) with very similar patterns of adaptation across the two arms. We observed that the nondominant arm presented a greater forward speed, a greater reactive force that was a direct consequence of the force field definition, similar deviation, and reduced correlation when compared with the dominant arm. We also showed that when confronted with randomly interleaved force field trials (experiment 2) participants increased the speed of their reaching movement even during trials where no force field was present. Moreover, in experiment 1 we observed that participants showed a better adaptation with their dominant arm with a good correlation between the adaptation of the two arms (Handedness is often understood as a specialization of the role of each arm. It has been suggested that the dominant arm relies more heavily on “predictive” control, using internal models of limb dynamics more efficiently (During the initial trials of the task, participants have no knowledge of the force field that will be applied to their arm. We consider the problem of reaching without an accurate model of the perturbation in the context of robust control (It has been shown that a modulation of reaching speed when confronted to a force field is linked to the use of a more robust control strategy (Interestingly, in experiment 1 we also observed that the nondominant arm was more impacted by the catch trials as shown by a greater PL, PL, and MS (Robust control differs from impedance control on two aspects. First, robust control assumes errors (or uncertainties) in the accuracy of the representation of the perturbation leading to an increased speed and vigorous response to perturbations (What our interpretation adds to the field can be understood in terms of the quality of internal representations used to perform reaching movements. First, we emphasize feedback control models because a clear difference arose in the correlation which includes online compensation throughout the whole movement (Interestingly, participants who showed a greater correlation with the dominant arm also showed a greater correlation with the nondominant arm (In experiment 2, we also observed difference between the two force field directions, with participants showing a greater adaptation to the perturbation for both arms for the inward oriented force field than for the outward oriented force fields (It has to be noted that participants were self-assessed right-handed and therefore could present different degrees in laterality. Indeed, previous studies have shown that the degree of laterality can impact the transfer of learning across the two arms (To conclude, our results highlight differences in adaptation and behavior between the two arms. We observed a tendency for both arms to use a more robust control strategy when facing perturbing force fields. As generally expected, the dominant arm showed better adaptation than the nondominant arm, with the nondominant arm relying on a more robust control strategy. Our results also suggest that both arms share a similar mechanism of adaptation.Acknowledgments: We thank Tanguy de Vermont for his help in the collection of the data.