Social scientists have focused on gratitude since the 1930s (Baumgarten-Tramer, 1938; Bergler, 1945, 1950; Gouldner, 1960; Heider, 1958; Schwartz, 1967; Simmel, 1950). Though it has been considered fundamental to the maintenance of reciprocity obligations between people (Gouldner, 1960; Simmel, 1950) and evolutionarily adaptive for its promotion of altruistic behavior (Trivers, 1971), the bulk of empirical research occurred over the past dozen years because psychological research was long dominated by a focus on pathology rather than flourishing (Seligman & Csik- szentmihalyi, 2000). Two classic studies—showing that expressing and experiencing gratitude bring peace of mind, satisfying personal relationships, and well-being (Emmons & McCullough, 2003; McCullough et al., 2002)—catalyzed the field, and since then a girth of research on gratitude and its applications have emerged.
