The first line of research investigates the effects of physical variables and seeks to understand the underlying coordinative processes of dyadic synergies that allow interactional synchrony to occur. To this end within-person coordination methodologies have been adapted to a between-person setting (Figure 1). These methodologies have involved the visual coordination of rhythmically moving limbs and the manipulation of variables that effect the oscillatory state of the system. A number of studies have demonstrated that the coordinative processes underlying dyadic rhythmic synergies are identical to those underlying within-person rhythmic synergies, namely, coupled oscillator dynamics. Supporting this claim is the fact that as two limbs of a single person or of two people are differentially weighted (thereby, increasing the difference between their preferred tempos or Aoo), a growing phase lag is observed between their cycles when they are swung at a common tempo (Schmidt, 1988; Schmidt, Shaw, & Turvey, 1993).