A motor abundance approach to augmented feedback for skill learning

In this study, the theoretical framework of motor abundance—specifically task-functional motor synergies—was applied to the design of augmented feedback for skill learning. A custom motor task involving a joystick-controlled plane was developed, where task success required coordinating hand velocity and thumb pressure to align with a predefined solution manifold. In Experiment 1, participants trained without augmented feedback over four 100-trial sessions, demonstrating learning through reduced error, increased UCM ratios, and lower motor synergy sample entropy, indicating within-trial redistribution of movement variance along the task-invariant dimension. Experiment 2 compared participants’ performance in a single practice session under three augmented feedback conditions: no feedback, lower-order sonification (separate mapping of velocity and pressure to sound), and higher-order sonification (sonification of deviation from the solution manifold). All groups improved similarly in performance and coordination structure, but higher-order feedback showed a trend toward greater alignment of movement variance along the manifold. Although not statistically conclusive, this pattern supports the idea that higher-order feedback can shape skill learning by educating attention to higher-order invariants. This study represents a first attempt to develop a theoretically grounded method for designing augmented feedback that leverages motor redundancy, with theoretical and practical considerations for future skill learning interventions.