Chapter 8 opens with the history of Rosa Parks, an African American woman who in 1955 refused to give up her seat for white passengers while riding on a Montgomery, Alabama, city bus. Parks’s arrest sparked a bus boycott during which African Americans chose to walk or carpool until the city reversed the law that imposed racial segregation on its buses. Despite the fact that other African Americans in Montgomery had performed the same protest in the months prior to Parks’s refusal to move, Duhigg argues: “When [Rosa Parks] was arrested, it triggered a series of social habits—the habits of friendship—that ignited an initial protest” (219)

Duhigg introduces the terms “strong ties” and “weak ties.” Strong ties are intimate, familiar relationships between family and friends. Weak ties are looser connections between members of a community. Both strong ties and weak ties are at the heart of all successful social movements. Parks, for instance, had strong ties with a robust group of family, friends, employers, NAACP members, and church members; she was deeply respected by people across both class and racial divides. In turn, those individuals had a broad network of weak ties across Montgomery’s larger population.