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Getting in the groove: study offers rare insight on physical interaction

Can a physical performance be spiritual? A new study says yes

More than a question of keeping time to the music or fine-tuning your footwork ahead of time, the dynamics of activities such as dancing are delicate and a new study says people fall into a specific pattern to avoid a collision.

And yet, dancing is not the only complementary, coordinated task during which this occurs.

"For instance, the same or similar movements are performed in a repetitive manner when two individuals are loading a dishwasher, stacking a pile of blocks or magazines, or dancing or (Kung Fu) fighting together," says lead author Michael J. Richardson of the University of Cincinnati in the US.

Richardson says his study is different from others exploring activities that involve inphase or antiphase synchronization -- the art of coordinating body movements in the same direction, or in opposing directions.

They are two basic types of coordination, but situations in which it's a question of avoiding collision require an even more complex pattern of coordinating body movement, says Richardson, whose study focused on the latter.

Working with 12 pairs of right-handed participants, all university students, he asked each pair to move objects of a 50-inch computer screen in tandem.

Using a hand-held motion-tracking sensor, they were asked to avoid bumping their objects into one another as they dragged their virtual goodies across the screen.

One partner was asked to drag the virtual pawn from the bottom left to the top right corner and the other was asked to drag his from bottom right to top left.

Participants stood back to back during the task, although they were able to see each other's pawn making its way across the screen.

"This task was chosen because many joint actions involve the continuous production of repetitive movements over time," write the authors.

Without instructions from the research team, participants fell into a stable rhythm of coordination in which one moved his pawn along a straight-line trajectory and the other chose an elliptical trajectory.

Turns out, this formula was the only way to do the task, so it was a mere question of finding this pattern, according to the study which was published in the Journal of Experimental Psychology: Human Perception and Performance.

Participants completed a total of 164 successful trials.

"Once you gain an understanding of normative dynamics, we can better diagnose when those dynamics are not working properly and also design interventions," says Richardson. "We've developed a dynamic model that captures the behavioral dynamics as well as provides a theoretical explanation of why certain behavior emerges between people as they learn to avoid each other while performing certain tasks."

The study has important implications for future research on autism, schizophrenia, sport rehabilitation and human interaction with robotics.