Affect control theory (ACT) is an empirically grounded, mathematical theory of social interaction. David R. Heise developed the theory in the early 1970s based on symbolic interactionist insights about the primary importance of language and of the symbolic labeling of situations. Inspired by the pragmatist philosophy of early symbolic interactionists, the theory begins with the premise that people reduce existential uncertainty by developing “working understandings” of their social worlds. The theory presumes that actors label elements of social situations using cultural symbols available to them. After creating this working definition, the theory further argues that actors are motivated to maintain it.