The movement of large crowds of people exhibit collective behavior that can be predicted with hydrodynamic theory disregarding individual behavior, according to a new study published in the journal Science. The research shows how people in crowds flow like water, overriding “interaction rules” that normally exist between people.
Researchers set up cameras above the starting line of three of the world’s biggest marathons: Chicago, Paris, and Atlanta. Cameras focused on the entire crowd as a single entity and applying hydrodynamic theory to the movement, free of individual behavioral assumptions.
“Mesmerizing impressions of virtually all patterns observed in bird flocks, fish schools, insect swarms, and even human crowds are effectively rendered…” ”by simple algorithms,” the authors said in the study.
Analyzing the movement of marathon runners at the starting line of the races, they were able to see waves of crowd density and velocity creating ripples in the crowd, cascading from the back and front of the line.
With mathematical models, researchers were able to predict how these crowd dynamics would play out from one starting line to the next.
However the authors noted, “Going beyond visual impressions and predicting the collective dynamics of groups of living creatures in response to physical, social, or biological imperatives, however, remains a formidable challenge.”
Researchers Bain and Bartolo warn in the conclusion of their paper on fluid-like behaviors of large crowds, once a large crowd is in movement there is no way to give orientational cues to thousands of people at once in motion.