Answer: Skinner's theory of operant conditioning.
Operant conditioning is a system that attempts to influence the strength of a behaviour by giving punishments or rewards. It was developed by B. F. Skinner in his 1938 book: "The Behaviour of Organisms: An Experimental Analysis."
The system can be divided in reinforcement, which is directed towards increasing the behaviour, or punishment, which tries to reduce it.
Both reinforcement and punishment can further be divided into positive (adding a stimulus) or negative (removing a stimulus).