Abstract
Bingham (2001; 2004a,b) proposed a dynamical model of coordinated rhythmic movement that predicted the information used was the relative direction of motion, modified by relative speed. de Rugy et al (2008) tested this prediction by testing the dependence on speed. They reported that movement stability did not depend on relative speed. However, there were limitations that cast doubt on these findings. Among them was the fact that the task used to test the model was not one the model was designed to represent. Snapp-Childs, Wilson and Bingham (submitted) replicated de Rugy et al.'s experiment and obtained results that supported the Bingham information hypothesis in contrast to the finding of de Rugy et al. We now revise the original Bingham model to apply to this new task, and then compare simulated data to the Snapp-Childs et al. data. To adapt the model to the new task, it had to be revised in three respects. First, the visual coordination task entailed uni-directional (not bi-directional) visual coupling. The revised model was used to simulate the switching experiment of Snapp-Childs et al successfully. Uni-directional coupling yielded a less stable system that switched at 1.25Hz rather than 3-4Hz. Second, the task required participants to control and produce specific amplitudes of movement (as well as specific frequencies and relative phases). This entailed another information variable, specifying amplitude, to be incorporated into the dynamical model to control and produce required amplitudes. Third, the task required that participants correct spontaneous deviations from required relative phases. The original Bingham model included perceived relative phase. This was now used to detect departures from required phases and to perform corrections. The resulting model successfully simulated the results replicated in Snapp-Childs et al. illustrating emphatically that perception-action models are required to model performance in coordinated rhythmic movement tasks.