A note on constant error shifts in post-perturbation responses

Response biasing was examined in the production of well-learned discrete timing responses. Interpolated movements consisted of trials which were briefly perturbed by an accelerating or decelerating force with subjects requested to amend the response in order to complete the trial successfully. Movement time analysis indicated that the response immediately following the perturbation trial demonstrated large biasing effects with the direction of the constant error shift a function of the direction of the perturbation. Responses following deceleration perturbations were produced too rapidly and those following acceleration perturbations were produced too slowly. Analysis of kinematic variables associated with these responses showed that post perturbation trials were characterized by systematic changes in peak acceleration and peak deceleration as well as the timing of these parameters. The biasing effects were temporary and showed other similarities to findings from short-term motor memory investigations. A number of differences were also noted along with methodological considerations for perturbation paradigms.