Cuban scientists have found that ants can be just as irrational as stampeding soccer fans. Panicking ants, like panicking people, follow the herd, and the herd makes some bad decisions.
Among humans, stampede behavior can be fatal, especially in enclosed areas like sports stadiums, dance clubs, and burning buildings. People will frequently—and illogically—jam up one door, blocking the exit, yet leave another door empty. "When you are in a real panic, you forget about reasonable strategies and just follow the crowd," says Ernesto Altshuler of the University of Havana. "In that sense, you are behaving a little bit like an ant."
In the study, Altshuler and his colleagues trapped ants in a circular chamber and then opened two identical exit doors. Calm ants used both doors equally. But ants panicked by insect repellent crowded around one exit and ignored the other.
Altshuler can't explain why ants, much less people, follow herd behavior. Once in stampede mode, their actions can be predicted by taking into account particle interactions like repulsion and friction, says Dirk Helbing, a physicist at the Institute for Transport and Economics at Dresden University of Technology in Germany.
Helbing was among the first to model crowds as discrete particles; his work inspired Altshuler, who usually studies superconductor vortices and granular avalanches. "I thought it could be fun to work with particles a little more intelligent than grains of sand," Altshuler says. "You don't see that very often in physics."