Can you explain the explosion of social activities like text messaging with little or no promotion of the behaviour? How a Mexican wave happens? The emergence of online communities? Or - more sensitively - the steady rise of floral roadside tributes to traffic accident victims from complete strangers? Unless you have a good explanation of mass behaviour, you'll have little chance of altering it.

Herd reveals that most of us in the West have completely misunderstood the mechanics of mass behaviour because we have misplaced notions of what it means to be a human being. With a host of...