Comparing errorful and error-free visuomotor adaptation to test for unintentional after-effects in observers


One proposition for how we learn from watching is via simultaneous covert activation of our motor system. There is conflicting evidence about the mechanisms that drive how observed errors impact subsequent movement. In visuomotor adaptation (VMA) paradigms where participants practice moving to targets with a rotation applied to their feedback, unintentional after-effects in the direction of the rotation is a robust effect. Among observers, although learning of the rotation occurs, after-effects are not shown. In an exception to this, compensatory after-effects in observers were evidenced when observers watched a confederate continuously miss (in the absence of a rotation). Therefore, we tested for the presence of after-effects among 3 groups (n=14/gp). A Rotation+Hit group observed an actor perform accurate reaches to a target with 30° rotated cursor feedback; a No-Rotation+Miss group observed errorful performance, where the actor consistently missed by 30° (so visual errors were matched). Group 3 did not observe. We compared performance in a normal environment, without vision in pre- and post-tests. Additionally, we tested for "learning" in the rotated environment. Despite evidence for direct effects of watching accurate reaches in Rotation+Hit group compared to the control group, there was no evidence of after-effects or implicit/motor based adaptation. Moreover, the Miss group showed no compensatory (or directional) after-effects. These data support other work showing that observational practice does not result in implicit adaptation of internal models for aiming, despite the fact that it is a useful way of acquiring new skills, arguably through more explicit, strategic means.

Acknowledgments: The third author would like to acknowledge Discovery grant funding from NSERC (Natural Sciences & Engineering Council of Canada) for this research.