Driven by recent empirical studies, we offer a new understanding of the degrees of freedom problem, and propose a refined concept of synergy as a neural organization that ensures a one-to-many mapping of variables providing for both stability of important performance variables and flexibility of motor patterns to deal with possible perturbations and/or secondary tasks. Empirical evidence is reviewed, including a discussion of the operationalization of stability/flexibility through the method of the uncontrolled manifold. We show how this concept establishes links between the various accounts for how movement is organized in redundant effector systems.
Latash is with the Dept of Kinesiology, Pennsylvania State University, University Park, PA 16802. Scholz is with the Dept of Physical Therapy and Biomechanics and Movement Science Program, University of Delaware, Newark, DE 19716. Schöner is with the Lehrstuhl Theoretische Biologie, Institut für Neuroinformatik, Ruhr-Universität Bochum, 44780 Bochum, Germany.