Cognitive activity shifts the attractors of bimanual rhythmic coordination

The attractors of bimanual rhythmic coordination are given as the solutions of a motion equation in relative phase. How are those attractors affected by cognitive activity? In 3 experiments, participants (N = 10 in Experiment s 1 and 2; N = 5 in Experiment 3) were required to produce in-phase or anti phase coordination while they either did or did not perform an information- reduction task. The average absolute deviation from in-phase (0 degrees) an d antiphase (180 degrees) satisfying a particular parameterization of the m otion equation was amplified by cognitive activity. That amplification of a bsolute phase shift was the same for both in-phase and antiphase coordinati on. Furthermore, the amplification tin degrees) increased linearly with the magnitude of cognitive activity tin bits). Cognitive activity had limited influence on the variability of relative phase and did not affect its avera ge signed deviation. Collectively, the results suggest that cognitive activ ity produces a shift in the attractors of bimanual coordination dynamics th at is directionally nonspecific and is independent of movement speed, detun ing, and the in-phase-antiphase distinction.