In this chapter, Duhigg discusses the effect of social identities on people’s thoughts, behaviors, and interactions, particularly when navigating difficult conversations. He starts by introducing the story of Dr. Jay Rosenbloom, a pediatrician who struggled to convince vaccine-hesitant parents to immunize their children. Despite providing ample information and evidence, Rosenbloom found that the more he tried to persuade these parents, the more they resisted.

Duhigg explains that the root of this resistance lay in the powerful grip of social identities—the self-images that individuals form based on their group memberships, cherished values, and deeply-held beliefs. He notes that social identities can exert a strong influence on people’s perceptions, causing them to exaggerate differences between groups and overemphasize similarities within groups. This tendency, Duhigg argues, can lead to the development and perpetuation of stereotypes and prejudice.

To illustrate this concept, the author presents various experimental studies, such as a 1954 study in which researchers divided boys at a summer camp into two groups, the Rattlers and the Eagles, and observed as the boys quickly formed intense bonds with their own faction while simultaneously demonizing and antagonizing the other group.

Duhigg then introduces the work of Claude Steele, a psychology professor who dedicated his career to studying the impact of stereotypes on academic performance.