State-, parameter-, and graph-dynamics: Constraints and the distillation of postural control systems

The seemingly effortless ability to maintain and adapt posture has traditionally been explained as the achievement of a single, relatively permanent postural control system. However, the extreme variability observed in postural performance challenges the idea that posture is controlled by a static system of fixed components. In this article we suggest that postural control is achieved by special-purpose, softly assembled postural devices that arise from parameter- and graph-dynamics. A brief summary of empirical studies utilizing nonlinear analyses of postural state dynamics is presented as evidence. Implications for this claim and future directions of research are also presented.