New Scientist has an excellent piece on how new research on the psychology of crowds is challenging the idea that people become an ‘unruly mob’ in large numbers. In fact, recent research shows that people tend to cooperate and quickly achieve an altruistic and bonded group identity when in large numbers.
This partly relies on the fact that our group identity is fluid, as demonstrated by an elegant experiment by crowd psychologist Mark Levine that the article touches on:
The fluidity of group psychology was also demonstrated in a 2005 experiment on English soccer fans by Mark Levine at the University of Lancaster, UK. He found that supporters of Manchester United who had been primed to think about how they felt about their team were significantly more likely to help an injured stranger if he was wearing a Manchester United shirt, rather than an unbranded shirt or one of rival team Liverpool.
However, fans who were primed to think about their experience of being a football fan in general were equally likely to help strangers in Liverpool shirts and Manchester United shirts, but far less likely to help someone wearing an unbranded one (Personality and Social Psychology Bulletin, vol 31, p 443). This shows the potency of group membership, and also how fluid the boundaries can be.
The article mentions several studies of dangerous crowd situations where there seems to have been large scale spontaneous co-operation that seemed to have averted more serious problems.
We recently covered research that found that the more people present at a confrontation, the less likely there is to be a violence outcome, although there were specific turning points where violence could go either way.
As the piece mentions, this is particularly interesting in light of a tactic called ‘kettling’ commonly employed by UK police to control large crowds. It involves surrounding the crowd and letting individuals leave but not letting anyone back in.
The psychology of this tactic was discussed by Bob Hughes, the head of training at the Metropolitan Police’s Public Order Unit, on a 2004 edition of BBC All in the Mind.
Interestingly, he describes it in terms of Maslow’s hierarchy of needs, where eventually the need to protest will be overtaken by the need to eat, drink, rest and so on, and so people will slowly disperse.
This is a distinctly individualistic approach to crowd psychology. It assumes that the crowd will be violent and so needs to be contained but that it can be broken down on an individual basis.
One implication from this new research on crowd psychology is that the kettling process itself may trigger violence on the first place, because it sets up a confrontational situation and strengthens the crowds’ group identity at the same time.
Link to NewSci piece on the ‘wisdom of crowds’.
Mind Hacks 
On kettling:
In order to get atoms to condense into a completely coherent state at very low temperatures (i.e., a Bose-Einstein condensate), physicists use an optical trap, which lets the highest energy atoms escape so that, over time, only the (smaller number of) more synchronized atoms remain, ultimately collapsing into a single mega-atom.
Just an analogy. But interesting to consider. The survivors are not the ones you want to be pushing together, right?