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.
Behavioural change theories
In 1985, Ajzen expanded upon the theory of reasoned action, formulating the theory of planned behaviour, which also emphasises the role of intention in behaviour performance but is intended to cover cases in which a person is not in control of all factors affecting the actual performance of a behaviour. As a result, the new theory states that the incidence of actual behaviour performance is proportional to the amount of control an individual possesses over the behaviour and the strength of the individual's intention in performing the behaviour. In his article, Further hypothesises that self-efficacy is important in determining the strength of the individual's intention to perform a behaviour. In 2010, Fishbein and Ajzen introduced the reasoned action approach, the successor of the theory of planned behaviour.