Book: Cricital Mass, by Philip Ball
Another interesting read was Critical Mass by Philip Ball, in which he explores how the complex behaviour of crowds - people, grains of sand or molecules - can be governed by each participating “agent” adhering to very simple rules. He uses insights from the field of statistical physics to model situations where human crowds interact, such as markets, audiences, electorates etc.
His point is that in order to explain the behaviour of crowds there is no need to look at the individual agents in too much detail. He acknowledges that his models are extreme simplifications of reality, but show that even with this gross simplification the rules of the agents’ interaction dictate the macroscopic behaviour of the group.