  Among the most-cited examples of a dynamical explanation of cognition is the Haken-Kelso-Bunz (HKB) model of coordination dynamics (Haken, Kelso, and Bunz 1985; Kelso 1995). This model, consisting of a single differential equation, captures the dynamics of coordinated finger wagging. Subjects are asked to wag their right and left index fingers either in-phase, where each finger moves toward and away from each other, or out-of-phase, like windshield wipers. As the rate of finger wagging increases, out-of-phase motion will “flip” to in-phase motion, but motion that starts in-phase will remain in-phase. In dynamical terms, the coordination of finger wagging has two attractors, or regions of stability, at slower speeds (in-phase and out-of-phase) but only one attractor at a higher speed (in-phase). The HKB model makes a number of predictions borne out by observation, for instance that there are only two stable wagging patterns at lower speeds, that erratic fluctuations in coordination will occur near the critical threshold at which out-of-phase wagging transforms to in-phase, and that deviations from out-of-phase wagging will take longer to correct near the speed of transformation to in-phase (see Chemero 2001 discussion).