Beyond error reduction: Dimensional analysis reveals qualitative differences in motor expertise

This study explores how motor expertise transforms across spatial dimensions. Three hundred data points were collected from twenty participants (ten experts and ten novices) who performed identical tasks across one-dimensional (1D) linear accuracy, two-dimensional (2D) planar precision, and three-dimensional (3D) angular coordination, captured by custom-built motion capture as participants executed strokes toward a suspended ball. The results revealed a progressive pattern of expertise effects. In 1D, experts showed moderately lower error; in 2D, the advantage became more pronounced; and in 3D, a qualitative difference emerged, as experts exploited larger movement angles while maintaining greater consistency. Dynamical systems analysis confirmed this distinction, with experts developing stable coordination patterns and novices exhibiting unstable ones. These findings extend traditional conceptualizations of expertise by showing that advanced skill transcends error reduction and involves the strategic organization of movement variability, providing a foundation for complexity-specific training protocols.