Activity theory is a tradition of psychological theory and research originating with the Soviet psychologist Vygotsky in the late 1920s and early 1930s. It was first developed by his colleagues Leont'ev, who coined the term, and Luria (Wertsch, 1981). Beginning in the 1970s, developmental psychologists and educational researchers in several other nations elaborated the theory and conducted empirical research, both quantitative and qualitative. In the United States, activity theory first influenced studies of literacy through the work of Scribner, Cole, and others at the Laboratory for Comparative Human Cognition. In the 1980s the theoretical tradition also became central to related lines of research into cognition in everyday life, particularly of adults engaged in labor and the acquisition of labor-specific practices through apprenticeship (Lave & Wenger, 1991; Rogoff, 1993). Although this tradition is by no means the dominant one in U.S. developmental psychology, activity theory is an increasingly important perspective.