Activity Theory: who is doing what, why and how

In simple terms, Activity Theory is all about 'who is doing what, why and how'. However, things are rarely that simple. Sometimes referred to as the Cultural-Historical Activity Theory (CHAT), Activity Theory is grounded in the work of the Russian psychologist Vygotsky and his students, in particular, Leontiev, in the 1920s. Activity Theory provides a lens with which to tease out and to better understand human activity.