Abstract des Autors

Two lines of research on the related skills of rhythmic bouncing a ball and juggling three balls were reviewed with the goal to reveal commonalities in the strategy typifying the dynamic systems approach to movement coordination. For both lines of research concepts from nonlinear dynamics and their experimental results were presented in parallel. While there were evident differences in the physical principles and key variables, the dual presentation demonstrated the similarity in the modeling strategy and the methodology. Criteria for the dynamically stable solutions defined the boundaries that the actor's movements had to satisfy in order to perform the rhythmic task. Essential in both approaches was that one key variable provided the reference frame for evaluating skilled performance and the process of learning. The role of perceptual information was evaluated by the decrement in stability of performance that selected perceptual manipulations induced. Individual differences between subjects in ball bouncing where shown to be the consequence of their choice of the key variable, which further constrained the kinematic properties across different movement realizations. Individual differences between expert jugglers were interpreted as their 'deliberate' choice of a solution that was not tightly constrained by maximum stability but rather one that afforded them more flexibility. This contrasting review aimed to show the spectrum of tools that a dynamic approach has to offer. It further showed that an analysis from a nonlinear dynamic perspective can establish a basis from which a set of important issues in motor control can be addressed, in a quantitative and physically principled manner. Verf.-Referat