Dynamics of 1 : 2 coordination: Generalizing relative phase to n : m rhythms

Interlimb rhythmic movements can be modeled as coupled oscillators, with st able performance characterized by the relative phase between the limbs. In the present study, that modeling strategy, verified previously for 1:1 coor dination, was generalized to 1:2 coordination with a view to n:m coordinati on. The generalized model predicted interactions between coordination (spec ifically, 1:1 vs. 1:2) and the frequency asymmetry between the limbs determ ining mean relative phase and its variability. The predicted interactions w ere evaluated with bimanual 1:2 and 1:1 rhythmic tasks in which participant s (N = 8) oscillated hand-held pendulums whose uncoupled frequencies could be adjusted so that different interlimb asymmetries were produced. The auth ors needed new analytic procedures to verify stable 1:2 coordination and to resolve stochastic and deterministic sources of variability in the compone nt oscillations. The major expectations from the generalized model were con firmed, and the implications of additional but unpredicted findings for the modeling of multifrequency behavior are discussed.