Solidarity, synchronization and collective action

For people to act collectively in actual situations---in contrast to public goods experiments---goal ambiguity, diversity of interests, and uncertain costs and benefits stand in their way. Under such conditions, people seem to have few reasons to cooperate, yet the Arab revolutions, as conspicuous examples, show that collective action can take place despite the odds. I use the Kuramoto model to analyze how people in a cohesive network topology can synchronize their salient traits (emotions, interests or other), and show that synchronization happens in a phase transition, when group solidarity passes a critical threshold. This model can yield more precise predictions of outbursts of collective action under adverse conditions, and casts a new light on different measures of social cohesion.