Behaviorism is a learning theory that focuses only on observable behaviors and disregards internal mental processes. Behaviorists define learning as acquiring new behaviors based on environmental conditions. Behavior is explained through stimulus-response without considering internal states. Major behaviorist theorists include Pavlov, Skinner, Thorndike, and Watson. Pavlov studied classical conditioning. Skinner researched operant conditioning. Thorndike proposed trial-and-error learning. Watson built on Pavlov's work and argued that reflexes are the basic unit of behavior. Behaviorism influenced classroom practices such as contracts, consequences, reinforcement, and behavior modification. Teachers administer positive or negative reinforcement to guide appropriate student behaviors.