Seattle Memorial Bridge incident

The Seattle Memorial Bridge incident took place in August 2001, when a woman who had stopped her car in traffic climbed over the bridge railing and a crowd urged her to jump. She leaped and fell sixteen stories, but survived. The book presents the episode not simply as an exceptional act of cruelty, but as a stark example of how individual behavior can gather force from the people around it.

The Incident

The woman was twenty-six. After she stopped her car and climbed over the railing, traffic quickly backed up behind her. On the other side of the highway, drivers slowed to look, bringing traffic there nearly to a crawl as well. Police arrived and tried to talk her down.

As the police attempted to keep her calm, drivers, pedestrians, and passengers on a stalled MetroBus shouted for her to jump. The crowd's calls continued despite the officers' efforts. She eventually jumped, falling sixteen stories to the river below; remarkably, she lived. The account gives the outcome without treating survival as a simple resolution: the crowd's behavior had helped turn an already dangerous situation into an immediate threat to her life.

The Baiting Crowd

The incident occurred in the morning, which the book describes as unusual, but the presence of a crowd egging on someone considering suicide by jumping was not unprecedented. Sociologist Leon Mann found that such crowds appeared in half of the cases he studied. They were more likely to act this way at night, when people could more easily remain unidentified and imagine themselves as part of a larger group.

Mann also found that the likelihood of people shouting increased with the size of the crowd. Anonymity helps explain why individuals may feel less accountable, but the account points to a further dynamic: as more people shout, others may become more willing to join them. The crowd is not merely a collection of separate onlookers; each person's conduct can alter the conditions under which the next person acts.

From Crowd Behavior to Collective Action

The book connects the baiting crowd to the broader behavior of rioting mobs and, by analogy, to the feedback loops that can drive a stock-market bubble. It uses Mark Granovetter's account of collective behavior to resist the idea that a mob suddenly becomes irrational as one body. In his model, some people are prepared to riot at almost any time, while others will not; most fall between those extremes, and their willingness to join depends on how many others are already participating.

Applied to the bridge incident, this framework makes the crowd's escalating conduct legible as a process of social influence rather than a single, inexplicable lapse. The Seattle episode is an unusually consequential case, but the mechanism the book draws from it is more general: seeing others participate can lower the threshold for joining in. The same accumulating participation helps explain how crowd behavior can become collective, and why a crowd's actions may intensify even when no one person directs them.