Effects of Social and Physical Variables on Between-Person Visual Coordination

Abstract Between-person visual coordination of rhythmic limb movements was investigated under manipulation of both social and physical variables. Each member of a pair of participants oscillated a hand-held pendulum at the same tempo, with both visually coordinating their movements so as to maintain the alternate phase mode. Participants' social competence was assessed and they were paired to produce three types of combinations: high-high (HH), low-low (LL), and high-low (HL). The frequency of oscillation (set by a metronome) and the preferred frequency differ- ence of the pendulum combinations (set by changing the relative lengths of the pendulums to be coordinated) were manipulated. Mean relative phase angle 4 and its variability were measured as indices of coordination. Standard results from interlimb coordination were replicated in the manipulation of the physical vari- ables: (a) More breakdowns in phase locking (defined as mean 4s outside the stable 130 deg. to 230 deg. range) were observed for the higher frequency of oscillation, (b) Relative phase lag changed proportionately with absolute difference in the pre- ferred frequency of the individual pendulums. Further, anomalous 4 standard- deviation results seemed to indicate a second source of fluctuations being caused by strong nonlinearities at the level of the component rhythmic units. Impor- tantly, the coordination was also affected by the social competence manipulations: HH and LL pairs demonstrated more breakdowns in phase locking than did the HL pair.