Dynamics of 1 : 2 coordination: Sources of symmetry breaking

Three asymmetries in the dynamics of 1:2 interlimb coordination were examin ed: the asymmetry in uncoupled frequencies, the asymmetry in coupled freque ncies, and the left-right functional asymmetry of the body. in a bimanual 1 :2 task, participants (N = 8) oscillated hand-held pendulums whose uncouple d frequencies were adjusted so that the first kind of asymmetry could be ma nipulated. For any given pendulum pair, the pendulum assuming the faster mo tion in the 1:2 coordination was oscillated in the right and the left hands . By assigning combinations of uncoupled eigenfrequencies and coupled task- specified frequencies across hands, the authors studied the interaction of all 3 asymmetries. The results confirm the appropriateness of generalized r elative phase as a collective variable for 1:2 coordination. Additionally, they suggest that the generalized form of the detuning parameter represents the first asymmetry and that the coupling function expresses the second as ymmetry. In 1:2 coordination, the body's functional asymmetry plays a limit ed role.