Activity theory – a conceptual framework originally developed by Aleksei Leontiev – has its roots in the socio-cultural tradition in Russian psychology. The foundational concept of the theory is human activity, which is understood as purposeful, mediated, and transformative interaction between human beings and the world. Since the early 1990s, activity theory has been a visible landmark in the theoretical landscape of Human-Computer Interaction (HCI). Along with some other frameworks, such as...