Ed Jones / AFP-Getty Images file

As the drums beat at machine gun speed and the guitars shred lightning fast, dozens of moshers flock to the center of the room and slam into one another. It looks like chaos as their bodies collide madly.

Like others, Jesse Silverberg believed that mosh and circle pits were random groups of people dancing wildly (and a bit violently). But five years ago, he took his girlfriend to her first (and last) heavy metal concert. Instead of jumping into the mosh pit at the In Flames show, he stayed with her on the outskirts. As the band played louder and the moshers presumably got drunker, Silverberg observed a pattern. One person would bump into another and the movement would ripple across the mosh pit.

“The collision went from one side to the other,” he says, adding it looked like moshers followed the rules of collective motion. “I had a hard time focusing on the music for the rest of the evening.”

Several years later in a statistical mechanics class with James Sethna, professor of physics at Cornell, Silverberg recalled the ripple-like movement in the mosh pit and thought studying it might make an interesting experiment. With the help of a fellow graduate student, Matt Bierbaum, Silverberg examined whether humans in mosh pits and circle pits truly followed the rules of collective motion, which describes phenomena such as flocking as seen with birds or schools of fish. (In mosh pits, people bounce off one another and in circle pits they rush around in a circular motion.)

They watched and analyzed about 100 videos from YouTube of people participating in either mosh or circle pits.

“I watched with pleasure,” says Silverberg. When he examined the dancers in mosh pits he realized that they behaved like gas particles bouncing around in the air in unpredictable ways. People in circle pits, on the other hand, dance in an ordered pattern, like flocks of migrating birds.

In addition to watching YouTube videos, the researchers used a computer simulation that measures collective behavior to see how moshers act. In the simulation, they created a fake concert venue and added a few conditions and Mobile Active Simulated Humanoids (what they call MASHers) —solid objects to resemble humans that enjoy dancing wildly to resemble moshers—to mimic real life concerts.

“If you just distribute the MASHers in the crowd they will [gravitate toward each other and begin moshing],” explains Bierbaum.

One MASHer follows the behavior of the neighboring MASHer, moving collectively, which is exactly what happens to moshers. “You can mix a bunch of people who want to dance wildly and people who do not [throughout the room] and the moshers end up in the center,” says Sethna.

Silverberg believes that understanding collective motion of moshers helps experts understand how people behave in emergencies such as fires or riots. Researchers can’t put people in a dangerous situation to learn how they evacuate in a panic. When they try simulating such events with the participants’ knowledge, people file out calmly, which is certainly not how they act in emergencies.

“Mosh pits become a lens to look into extreme situations,” explains Silverberg, who funded the study himself (read: he bought all his own concert tickets).

The paper has been submitted for publication, but is available as a preprint online.

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