Shortly after the popular uprising that led to the establishment of the Paris Commune in 1871, the politician Georges Clemenceau recalled witnessing a riot: “Suddenly a terrific noise broke out, and the mob which filled the courtyard burst into the street in the grip of some kind of frenzy…All were shrieking like wild beasts without realising what they were doing.” For those who followed the English riots of 2011, the terms are familiar. On television, in newspapers and comment threads, the rioters were repeatedly likened to animals in the grip of a primitive frenzy, induced not by drink or drugs but by another culprit: the crowd.

Crowds, we are often told, are dumb. They obliterate reason, sentience and accountability, turning individuals into helpless copycats. Commentators on the riots offered different explanations but most agreed that crowd psychology was part of the problem. “The dominant trait of the crowd is to reduce its myriad individuals to a single, dysfunctional persona,” wrote the novelist Will Self in the New Statesman. “The crowd is stupider than the averaging of its component minds.” The violence was said to have spread like a “contagion” through the crowd, facilitated by social media. For those who wanted to sound scientific, the term to drop was “deindividuation”: the loss of identity and moral responsibility that can occur in a group. But do crowds really make us more stupid?

Earlier this year, the world watched a crowd bring down an autocratic government, by the simple act of coming together in one place, day after day, night after night. Egyptian protesters created a micro-society in Tahrir Square, organising garbage collection, defending themselves when they needed to, but otherwise ensuring the protest remained peaceful. As well as courage, this took intelligence, discipline and restraint. Few international observers accused the crowd in Tahrir Square of being dysfunctional, or of turning its members into animals. The Tahrir protesters also used social media, but rather than calling for a ban, as some in Britain did after the riots, people wrote eulogies to the liberating potential of Twitter. It seems that not all crowds are bad. But when bad things happen, the crowd gets the blame.

Consciously or otherwise, Self and others are echoing the French intellectual, and contemporary of Clemenceau, Gustave Le Bon. In 1896 Le Bon published the most influential book ever written about crowds, “The Crowd: A Study of the Popular Mind”. “By the mere fact that he forms part of an organised crowd,” Le Bon argued, “a man descends several rungs in the ladder of civilisation. Isolated, he may be a cultivated individual; in a crowd, he is a barbarian.” Le Bon was the Malcolm Gladwell of his day, a populariser of scientific thought with an acute feel for the Zeitgeist. His equivalent of Gladwell’s “tipping point” was “the law of the mental unity of crowds”. It was a scientific-sounding articulation of an old idea: crowds have a mind of their own, under which individuality is submerged and rationality destroyed.

Le Bon’s book hit a cultural nerve: a phrase of his, the “era of crowds”, stuck to the late 19th century. Europe’s cities had grown and industrialised fast, creating a vast and unruly class of people who had a nasty habit of coming together in public places to demand things. In Paris riots had threatened and sometimes overturned the established order for the last hundred years. Le Bon was a conservative, distrustful of fashionable democratic ideas. Like other members of the French middle class, when he saw a crowd he smelt only trouble. It’s hardly surprising that he would characterise the people in them as sub-human.

What is surprising is that we seem to have inherited his prejudices. John Drury, a psychologist at Sussex university who studies crowd behaviour, believes that the idea that crowds induce irrational behaviour and erase individuality just isn’t supported by the evidence. First, most crowds aren’t violent. The crowd in the shopping mall or at a music festival is usually calm and ordered. Even crowds that include conflicting groups, as at football matches, are more likely to be peaceful than not. Second, even when crowds do turn violent, they aren’t necessarily irrational. In the 18th century England was afflicted by food riots. If ever there was an atavistic reason to riot, that was surely it. But the historian E.P. Thompson showed that the riots took place not when food was at its most scarce but when people saw merchants selling grain at a steep profit; the rioters were motivated by a rational sense of injustice rather than the “animal” drive of hunger.

The Le Bon way of thinking about crowds matches the popular perception of crowd disasters, too—we tend to assume the worst of those involved. The people of Liverpool have spent years correcting the unfounded characterisation of those involved in the Hillsborough disaster as mindless thugs. In 1979, at a concert in Cincinnati headlined by The Who, 11 people were crushed to death as fans lined up to enter the stadium. The press described a “surging, primitive mob” comprised of “barbarians” and quoted a security guard who said, “These kids were acting like animals.” But a subsequent study based on other eyewitness interviews found that, rather than engaging in a crazed stampede to get the best seats, crowd members had attempted to help each other escape the crush as soon as they realised it was happening. In fact, the problem in such situations is almost always one of physics, rather than morality; a little pushing can create shock waves that ripple through a crowd, exerting ferocious pressure on those unfortunate enough to be caught in the most tightly packed areas or up against a hard object, like the Who fans closest to the locked doors, or the Liverpool supporters nearest the barrier.

Crowds can change the way people behave. There is a difference between what you might call an accidental crowd, as in a railway station, and an organised crowd: people brought together by a shared purpose—supporting a team, overthrowing a despot. Being a part of such a crowd can lead you to do things you wouldn’t normally do and might even disapprove of in normal circumstances: chant, swear at a referee, bellow the chorus to Robbie Williams’s “Angels”. But that’s not to say that the persona you adopt in this context isn’t “you” or that it’s irrational to take part in crowd rituals (in a crowd of Barcelona supporters, the irrational thing to do would be to cheer on Real Madrid). When an accountant plays air guitar at a concert, he isn’t giving up his identity so much as finding a neglected corner of it. Above all, he is enjoying the glorious sensation of feeling part of something bigger than himself.

An accidental crowd can become an organised one in response to an external threat. Passengers on the Piccadilly line who left King’s Cross at 8.50am on July 7th 2005 would have felt little in common with each other, bar the tetchiness of the commuter. But when the carriage exploded and the survivors realised they had been attacked, they performed heroic acts to save the lives of strangers they had just been ignoring. The Tahrir Square crowd included supporters from Cairo’s leading soccer teams, Al-Ahly and Al-Zamalek. The two groups have a longstanding post-match tradition of vicious fighting. Yet in Tahrir Square they stood together against Mubarak’s thugs. Crowds are as likely to bring out the best in us as the worst.