Horsing Around: Spontaneous Four-Legged Coordination

ABSTRACT

Motivated by previous research suggesting that informational and mechanical interlimb coupling can stabilize rhythmic movement patterns, the authors show that stable 4-legged patterns between 2 individuals, either walking or running, can emerge unintentionally from simple forms of coupling. Specifically, they show that the leg movements of pairs of naive individuals become spontaneously phase locked when visually or mechanically coupled via a foam appendage. Analysis of each of the phase locked trials revealed distinct preferences for particular 4-legged patterns, with interpersonal in- and anti-phase coordination patterns (equitable with quadruped pace and trot, respectively) observed almost exclusively. Preference for either pattern depended on the strength of coupling. The authors discuss these findings in light of previous claims that the patterns of human and animal locomotion—as well as coordinated movements in general—can emerge from lawful coupling relations that exist between the subcomponents of perceptual-motor systems.

Keywords:

• coordination dynamics
• interpersonal coordination
• mechanical coupling
• quadruped gait
• visual coupling

ACKNOWLEDGMENTS

The authors thank Veronica Romero and Michele Chu for help with data collection and Damian Stephen for help in developing and running a pilot experiment. This research was supported in part by grants from the Provost's Office at the University of Connecticut and by the National Science Foundation (award #BCS-0750190).

Notes

1. A control parameter is a system parameter that when changed beyond some critical value induces a qualitative change in the order of the system. Note that the phrase control parameter does not refer to a system property that prescribes the observed pattern or change in pattern. It simply refers to a parameter that leads the system through the variety of possible patterns (Kelso, 1997).