Contextual interference refers to the phenomenon whereby a blocked practice schedule results in faster acquisition but poorer retention of new motor skills compared to a random practice schedule. While contextual interference has been observed under a broad range of tasks, it remains unclear if this effect generalizes to the implicit and automatic recalibration of an overlearned motor skill. To address this question, we compared blocked and random practice schedules on a reaching task in which we used a feedback perturbation method that isolates implicit adaptation. The degree of implicit adaptation was quantified as the change in hand angle in the opposite direction of the perturbation, and retention was quantified as the percent of adaptation remaining after visual feedback was extinguished. In two experiments, participants tested under a random practice schedule exhibited slower implicit adaptation, but better retention compared to participants tested under a blocked practice schedule, the signature of contextual interference. These results indicate that contextual interference is not limited to the acquisition of new motor skills but also applies to the implicit adaptation of established motor skills.

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