Abstract
Successfully meeting a shared goal usually requires co-actors to adopt complementary roles. However, in many cases, who adopts what role is not explicitly predetermined, but instead emerges as a consequence of the differences in the individual abilities and constraints imposed upon each actor. Perhaps the most basic of roles are leader and follower. Here, we investigated the emergence of “leader-follower” dynamics in inter-personal coordination using a joint supra-postural task paradigm (Ramenzoni et al., 2011; Athreya et al., 2014). Pairs of actors were tasked with holding two objects in alignment (each actor manually controlled one of the objects) as they faced different demands for stance (stable vs. difficult) and control (which actor controlled the larger or smaller object). Our results indicate that when actors were in identical stances, neither led the inter-personal (between actors) coordination by any systematic fashion. Alternatively, when asymmetries in postural demands were introduced, the actor with the more difficult stance led the coordination (as determined using cross-recurrence quantification analysis). Moreover, changes in individual stance difficulty resulted in similar changes in the structure of both intra-personal (individual) and inter-personal (dyadic) coordination, suggesting a scale invariance of the task dynamics. Implications for the study of interpersonal coordination are discussed.
Highlights
Two friends passing a cup of coffee involves the coordination of no fewer than 2 arms, 8 joints, and 50 muscles spread across two separate bodies
Analogous increases in our laminar measures (LAM and TT) indicate that flexibility decreased in a commensurate manner. These changes tracked with the increases in the combined stance difficulty—when both actors were in the Easy stance their combined stance difficulty was relatively lower than the challenges faced when both actors were in the Hard stance, while mixed conditions were intermediary
The pattern of inter-personal coordination effects is consistent with our observed intra-personal effects
Summary
Two friends passing a cup of coffee involves the coordination of no fewer than 2 arms, 8 joints, and 50 muscles spread across two separate bodies. Each person must, at minimum, continuously track the positions and orientation of one another’s hands, and act so as to mutually align their movements within a very narrow window of space and time. These sorts of exacting perceptual and motor demands are necessary in even the most basic of joint tasks. According to the inter-personal synergy hypothesis (Riley et al, 2011), the coordination of joint actions between individuals is the result of similar processes—mutual constraint and synergistic organization across two or more people’s bodily and cognitive states
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