Crowd Psychology and Lessons We Still Ignore

The recent riots in Baltimore made me wonder about crowd psychology and control, among other topics. Is there a critical tipping point toward violence that we can avoid, or a proven way to cut short a rampage once it starts? How do we prevent peaceful protesters from turning into a rock-throwing, looting mob? Given our long history of urban riot, you'd think we would know better how to handle volatile crowds by now. Unfortunately, the new trend to militarized-looking police response may actually set back initial crowd control; those shields, helmets and armored vehicles distance communities from the police as people and turn them into a faceless occupying force to resent. Combine that with a relatively small police presence, and the tipping point comes because the cost of participating in violence--the risk of going to jail--gets low enough as crowd numbers overwhelm law enforcement numbers. After things spin out of control, only armed troops in curfew-emptied streets scatter the mob. Apparently, we still need to improve our understanding of crowd psychology. Back in 1895, Gustave LeBon pointed out the dangerous anonymity and behavioral contagion of crowds, which cause individuals to abandon personal responsibility for conformity with group emotions. Crowd psychology theorists define crowds by their aggressive, escapist, acquisitive, or expressive behaviors. The escapist crowd is just panicked people fleeing danger (what you get when you yell "Fire" in a theater). An expressive group gathers for a joint purpose (rock concert, civil disobedience, religious inspiration). An aggressive mob is outwardly violent (rioting and arson), while the acquisitive mob is fighting for limited resources (looting). Crowds in Baltimore at any one time probably fit into all four categories. So is there a general riot control formula we're missing? Edward Glaeser, a Harvard University economics professor, has argued that a comparison of crowd control examples supports a large initial police presence with a mass arrest/light penalty formula, basically nonviolent clearing of the streets, as the best way to stave off escalating violence. For an interesting but brief discussion of the history of American riots, see Glaeser's 2011 Bloomberg News article: http://www.bloomberg.com/news/articles/2011-08-12/how-riots-start-and-how-they-can-be-stopped-edward-glaeser