Negative reinforcement aims to increase behaviors by removing unpleasant stimuli. It involves an establishing operation, discriminative stimulus, behavior, and removal of the establishing operation. There are three types of negative reinforcement contingencies: escape, avoidance, and free-operant avoidance. An example is a mother picking up her crying child, removing the unpleasant stimulus of crying and increasing the likelihood of the child signaling for pickup in the future. Negative reinforcement can encourage good behaviors but effectiveness depends on the individual.