Activity theory
Activity theory (AT; ) is an umbrella term for a line of eclectic social sciences theories and research with its roots in the Soviet psychological activity theory pioneered by Lev Vygotsky , Alexei Leont'ev and Sergei Rubinstein. These scholars sought to understand human activities as systemic and socially situated phenomena and to go beyond paradigms of reflexology (the teaching of Vladimir Bekhterev and his followers) and classical conditioning (the teaching of Ivan Pavlov and his school), psychoanalysis and behaviorism. It became one of the major psychological approaches in the former USSR, being widely used in both theoretical and applied psychology, and in education, professional training, ergonomics, social psychology and work psychology.
Behavioral activation
Behavioral activation comes under the heading clinical behavior analysis or what is often termed third generation behavior therapy. Other behavior therapies are acceptance and commitment therapy (ACT), as well as dialectical behavior therapy (DBT) and functional analytic psychotherapy (FAP). Behavioral activation owes its basis to Charles Ferster's "Functional Analysis of Depression" (1973) which developed B.F. Skinner's idea of depression, within his analysis of motivation, as a lack of reinforcement.