Who introduced principles of reinforcement?

The concept of reinforcement was given by Edward Thorndike in his theory of Connectivism/ Connectionist theory of learning. He gave three laws - Law of readiness,Law of exercise and Law of effect.

The law of effect in particular talks about reinforcement; "responses that produce a satisfying effect in a particular situation become more likely to occur again in that situation, and responses that produce a discomforting effect become less likely to occur again in that situation". Here, the satisfying situation/effect become a reinforcer, positive or negative.