Crowds of people are often seen as bad for public order. But they have ways of policing themselves that the police might do well to understand

Eyevine

ACCORDING to a much-reported survey carried out in 2002, Britain then had 4.3m closed-circuit television (CCTV) cameras—one for every 14 people in the country. That figure has since been questioned, but few doubt that Britons are closely scrutinised when they walk the streets. This scrutiny is supposed to deter and detect crime. Even the government's statistics, though, suggest that the cameras have done little to reduce the worst sort of criminal activity, violence.

That may, however, be about to change, and in an unexpected way. It is not that the cameras and their operators will become any more effective. Rather, they have accidentally gathered a huge body of data on how people behave, and particularly on how they behave in situations where violence is in the air. This means that hypotheses about violent behaviour which could not be tested experimentally for practical or ethical reasons, can now be examined in a scientific way. And it is that which may help violence to be controlled.

One researcher who is interested in this approach is Mark Levine, a social psychologist at Lancaster University in Britain who studies crowds. Crowds have a bad press. They have been blamed for antisocial behaviour through mechanisms that include peer pressure, mass hysteria and the diffusion of responsibility—the idea that “someone else will do something, so I don't have to”. But Dr Levine thinks that crowds can also diffuse potentially violent situations and that crime would be much higher if it were not for crowds. As he told a symposium called “Understanding Violence”, which was organised by the Ecole Polytechnique Fédérale de Lausanne in Switzerland earlier this month, he has been using CCTV data to examine the bystander effect, an alleged phenomenon whereby people who would help a stranger in distress if they were alone, fail to do so in the presence of others. His conclusion is that it ain't so. In fact, he thinks, having a crowd around often makes things better.

Crowd control

The dynamics of crowd behaviour are hard to study, not least because people are not reliable witnesses of their own behaviour. But Dr Levine persuaded the authorities in one British city to allow him to look at their CCTV footage of alcohol-fuelled conflict in public places, suitably anonymised to comply with privacy and data-protection laws. He analysed 42 clips of incidents that operators in a control room had judged had the potential to turn violent, though only 30 of them actually did so. He recorded gestures he labelled either “escalating”, such as pointing and prodding, or “de-escalating”, such as conciliatory open-handedness.

His first observation was that bystanders frequently intervene in incipient fights. The number of escalating gestures did not rise significantly as the size of the group increased, contrary to what the bystander effect would predict. Instead, it was the number of de-escalating gestures that grew. A bigger crowd, in other words, was more likely to suppress a fight.

Some incidents did end in violence, of course. To try to work out why, Dr Levine and his colleagues constructed probability trees to help them calculate the likelihood that a violent incident such as a punch being thrown would occur with each successive intervention by a bystander. Using these trees, they were generally able to identify a flashpoint at which the crowd determined which way the fight would go.

Judging the fight to begin with the aggressor's first pointing gesture towards his target, the researchers found that the first intervention usually involved a bystander trying to calm the protagonist down. Next, another would advise the target not to respond. If a third intervention reinforced crowd solidarity, sending the same peaceful message, then a violent outcome became unlikely. But if it did not—if the third bystander vocally took sides, say—then violence was much more likely.

Dr Levine talks of a “collective choreography” of violence, in which the crowd determines the outcome as much as the protagonist and the target do, and he is now taking his ideas into the laboratory. In collaboration with Mel Slater, a computer scientist at University College, London, he is looking at the responses of bystanders to violence recreated in virtual reality.

Dr Slater has pioneered this approach, since people seem to react to virtual reality as they do to real life, but no one gets hurt and conditions can be controlled precisely. Because the participants know it is not real, many of the ethical obstacles to placing them in such situations are removed. But Dr Slater proved the tool's usefulness in 2006, when he used it to recreate a famous experiment conducted in the 1960s by Stanley Milgram, an American psychologist. Milgram showed that ordinary people would obey orders to the point of delivering potentially lethal electric shocks to strangers—an experiment that, even though nobody really received any shocks, would be ruled out today, on ethical grounds. Dr Slater's volunteers behaved similarly to Milgram's.

Virtual reality may thus allow Dr Levine to understand the collective choreography of violence better than he does now, but he is already convinced that, despite the moral panic over violence in Britain today, the influence of groups is largely benign. His work could have practical consequences, since police generally aim to break crowds up. If he is right, that approach may unintentionally lead to more fights. It sounds counter-intuitive, but many of the best ideas are. And if it is true, then perhaps Big Brother could give up the CCTV habit and go and do something more useful instead.