Behaviorism is a theory of learning that focuses on observable behaviors and interactions with the environment, without consideration of internal mental states. There are two major types of conditioning: classical conditioning, where a stimulus is paired with a response; and operant conditioning, where behaviors are reinforced through rewards or punishments. Major thinkers in behaviorism include Ivan Pavlov, B.F. Skinner, John B. Watson, Edward Thorndike, and Clark Hull. Behaviorism can be applied in classroom settings through positive and negative reinforcement of behaviors.