Leon Mann

Leon Mann appears as a sociologist whose research helps explain how a crowd can shape individual conduct. The book cites his study of people who had stopped at a height and were at risk of jumping, noting that in half the cases he examined, crowds gathered and encouraged them to do so. Mann’s work gives the chapter’s discussion of crowd behavior a concrete social mechanism: what people do can depend on the visible actions of others around them.

Mann’s Research on Baiting Crowds

The book introduces Mann through a Seattle incident in August 2001, when a woman stopped her car on the Seattle Memorial Bridge and climbed over the railing. Traffic accumulated behind her, while drivers on the other side slowed to watch. As police tried to talk her down, people among the drivers, pedestrians, and passengers on a stalled MetroBus urged her to jump. She did, falling sixteen stories into the river, but survived. The episode is presented as an unusually public example of the baiting behavior Mann had studied.

Mann found that crowds were most likely to encourage a person at night. Darkness, the book suggests, made it easier for people to avoid identification and to imagine themselves as part of a larger group. Crowd size mattered as well: the larger the gathering, the more likely it was that people would shout. Anonymity offers one explanation, but Mann’s findings also point to a reinforcing dynamic: as more people yell, others may become more willing to join them.

From Crowd Behavior to Collective Action

The account distinguishes baiting crowds from the broader dynamics of rioting. Such crowds are relatively rare, but the mechanism that drives them resembles the way a violent mob can form. The comparison is not that every crowd becomes violent; it is that collective behavior can develop through interactions among people whose readiness to act differs.

The book connects Mann’s research to sociologist Mark Granovetter’s account of riots. In Granovetter’s model, some people will not riot, some are ready to do so almost immediately, and many lie between those extremes. The middle group’s willingness depends on how many others are already participating. In this framework, the visible behavior of a crowd can draw additional people into action without requiring a single shared plan or a sudden collective loss of reason.

Significance in the Book

Mann’s research helps the book challenge the idea that extreme crowd behavior is simply a matter of individuals losing their minds. The Seattle scene shows how public pressure can intensify around a person in danger, while the research identifies crowd size, anonymity, and the participation of others as conditions associated with that pressure. The analysis then broadens from the bridge to mobs and financial bubbles: in each case, people can take cues from the surrounding group, and collective behavior can become more extreme than the judgment of any one person. Mann’s contribution is thus part of the book’s distinction between a crowd’s capacity for shared judgment and the harmful force of a crowd caught in a reinforcing pattern.