title: Motor learning: changes in the structure of variability in a redundant task.
abstract: Although variability is a fundamental and ubiquitous feature of movement in all biological systems, skilled performance is typically associated with a low level of variability and, implicitly, random noise. Hence, during practice performance variability undergoes changes leading to an overall reduction. However, learning manifests itself through more than just a reduction of random noise. To better understand the processes underlying acquisition and control of movements we show how the examination of variability and its changes with practice provides a suitable window to shed light on this phenomenon. We present one route into this problem that is particularly suited for tasks with redundant degrees of freedom: task performance is parsed into execution and result variables that are related by some function which provides a set of equivalent executions for a given result. Variability over repeated performances is analyzed with a view to this solution manifold. We present a method that parses the structure of variability into four conceptually motivated components and review three methods that are currently used in motor control research. Their advantages and limitations are discussed.
authors.affiliation: Institute for Movement Science, Justus-Liebig-University of Giessen, Germany. hermann.mueller@sport.uni-giessen.de
authors.forename: Hermann
authors.initials: H
authors.lastname: Müller
authors.forename: Dagmar
authors.initials: D
authors.lastname: Sternad
mesh_terms: D000704:Analysis of Variance; D001132:Arm / Q000502:physiology; D006801:Humans; D007858:Learning / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology; D009068:Movement / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D012016:Reference Values; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis