Activity Theory (AT)
Activity Theory (AT) is a comprehensive collection of sciences that was (and is) popular in Russia and the former Soviet Union. It is rooted in psychological theories pioneered by Soviet researchers Alexei Leont'ev and Sergei Rubenstein.
This primarily Russian (and former USSR) theory sought to understand all of human physical and social activities as complex and socially situated phenomena that expands upon and fuses the teachings of earlier Russian researchers Bekhterev and Pavlov, as well as the schools of psychoanalysis and behaviorism. This theory is still popular and in wide use in the former Soviet Union in the fields of psychology, education, professional training, and ergonomics.