The concept of activity in Soviet psychology

The concept of activity plays as important and ambiguous a role in Soviet psychology as did the concept of behavior in American studies circa 1920 to 1950 and the concept of consciousness in European psychology of the late nineteenth century. Activity has been the chief category of psychological research in contemporary Soviet psychology since the beginning; and exactly for that reason, the concept of activity has been extremely difficult for Soviet psychologists to define clearly. Since the time of its inception in the 1920s, this category has undergone a metamorphosis and has been the subject of so many disputes that it cannot be adequately comprehended out of the context of its history.