Behaviorist theory believes all behavior is learned through stimulus-response and shaped by reinforcement or punishment. B.F. Skinner's work in operant conditioning showed that behavior is influenced by environmental factors. Positive reinforcement uses rewards to increase a behavior. Negative reinforcement decreases an unpleasant behavior. Punishment decreases an undesirable behavior by introducing an adverse stimulus or removing a positive one. Behaviorists aim to determine effective reinforcements and punishments for students through consistency and timing responses close to behaviors.