According to coercion theory (Patterson, 1982, 2016), children's aggression is developed and maintained through transactional processes between parents and their children that unfold over time. The theory provides a model of the behavioral contingencies that explain how parents and children mutually "train" each other to behave in ways that over time increase the likelihood of children's aggression and decrease parents' control over this aggression. Although the theory characterizes the interactions that often lead to dysfunctional family processes and children's aggression, its focus on observable, interpersonal negativity has resulted in research that largely overlooks intraindividual phenomena, such as the internal experiences that drive parents' expressed negativity. In this article, I present empirical and theoretical work that supports an expanded focus of coercion theory to include emotion as an internal mechanism of reinforcement that facilitates and maintains coercive family processes and children's antisocial development.