The history of how crowds got such a bad name is a long one. We could point to the coming of urbanisation and mass democracy, or the damning theories of groupthink laid out by Freud, and Mussolini’s favourite psychologist Gustave Le Bon. The most intriguing contribution of all, however, comes from John Calhoun and his experiments on rats.

As a scientist for the US government from the 1950s to the 1980s, Calhoun was obsessed with testing the psychological effects of crowding. Out in the Maryland countryside, he created a “rodent universe”: room-sized pens amply stocked with food, water and bedding. The only restriction Calhoun put on his rats and mice was space – and as they rapidly bred, the “rat utopias” turned into lab versions of Sodom and Gomorrah.

Young male rats formed gangs that preyed on females. Mothers abandoned their babies, then attacked them. Some rats mounted any animal they could. Cleaning the pens, Calhoun’s assistants would find discarded rodent skins turned inside out – the creature within had been eaten whole.

All those who saw urban overcrowding as leading to degeneracy could now claim science was on their side. Calhoun would himself begin papers by quoting Malthus’s view that “vice and misery impose the ultimate natural limit on the growth of populations”.

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Yet the argument that simply putting lots of humans in close proximity to each other leads to social breakdown has never stacked up. The well-heeled inhabitants of Park Avenue’s apartment blocks don’t live in the scientist’s dystopia; in South Central LA, on the other hand, lack of space isn’t a problem, but lack of money is.

http://www.guardian.co.uk/commentisfree/2010/apr/06/rats-humans-brain-food