As someone who dislikes crowds, listener Graham is curious about them. Crowds gather in all sorts of places, from train stations and football matches, to religious events and protest marches. But is there a science behind how they move and behave? To find out, Anand Jagatia speaks to some actual crowd scientists.

He learns about the psychology of social identity, which influences everything from how close we stand to others to how we react in emergencies. He visits the Athens marathon, and hears about the algorithm that predicts how 50,000 runners will move through a city on race day. And he explores research into the science of riots, which explains why some peaceful crowds turn violent.

Presented and produced by Anand Jagatia

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Archive: BBC News