Movement kinematics as an index of the level of motor skill: the case of Indian craftsmen stone knapping.

What are the differences between the movements of an expert exhibiting superior performance compared with those of a novice or even an experienced person? Adopting a functional approach to tool use, this study presents results from experimental field research on stone knapping from Indian craftsmen of different levels of skill. The results showed that the differences in the levels of motor skill appeared in movement variability rather than in particular kinematic content. The higher is the level of motor skill, the more kinematic solutions are used, the more stable are the functional and the more variable the nonfunctional joint loadings. This study strongly suggests that to really understand learning processes and motor expertise, naturalistic challenging activities that require years of practice need to be elicited.