Concept: Operant conditioning is a learning method where behaviors are strengthened by rewards or weakened by punishments. It was pioneered by B.F. Skinner. Explanation: Skinner conducted experiments using a Skinner box with a rat. When the rat pressed a lever, it received a food pellet. This reward increased the likelihood of the rat pressing the lever again. This type of learning focuses on voluntary actions, called operants. Other psychologists proposed different theories: Pavlov (classical conditioning), Thorndike (trial-and-error), and Kohler (insight learning). Only Skinner is associated with operant conditioning. Answer: B. Skinner