Movement Forms: A Graph-Dynamic Perspective

Abstract

The focus of this article is on characterizing the physical movement forms (e.g., walking, crawling, rolling) that are used to actualize abstract, functionally-specified behavioral goals (e.g., locomotion). Emphasis is placed on distinguishing such forms by their topological patterns of physical contact between agent and environment (i.e., the forms' physical graphs) and the transitions among these patterns displayed during skilled performance (i.e., the forms' physical graph dynamics). Crucial in this regard are the creation and dissolution of loops in these graphs, which can be related to the distinction between open and closed kinematic chains. Formal similarities are described within a task-dynamics framework between the physically-closed kinematic chains (physical loops) created during skilled actions and the functionally-closed kinematic chains (functional loops) associated with task-space control of end-effectors; we argue that both types of loop must be flexibly incorporated into the coordinative structures governing skilled action. Finally, implications of the graph-dynamic perspective are discussed for understanding patterns of inter-agent coordination and the perceptual guidance of action using informational links between agents and spatially remote (nonsentient) environmental objects.