Motor abstraction training generalizes to the refinement of specific movement patterns

The ability to abstract the invariant structure of an experience while discarding incidental details underlies generalization across virtually every domain of human cognition, from vision and language to concept learning. Yet whether the motor system generates such abstractions and whether they causally contribute to skill learning remain open questions. Here, we introduce a paradigm in which human participants learned to refine novel movement patterns by learning to precisely copy unfamiliar handwritten characters. To examine the role of motor abstractions in this form of motor learning, participants were trained on markedly rotated versions of the characters, which recruited substantially different lower-level movements while still maintaining the relevant abstract movement trajectory. Across eleven experiments, abstraction training drove robust skill improvements that were comparable to having repetitive practice on the canonical form of each character. Moreover, this learning was largely motoric in nature: it did not require a visual template, sustained trajectory feedback, or mental imagery, and was sensitive to the sequential structure of the movement trajectory. These findings establish a causal role for abstractions in motor learning, revealing that the motor system likely deploys abstractions in the earliest stages of skill acquisition.