Learning is a fundamental aspect of psychology, relating to how organisms learn, remember, and apply knowledge and behaviors. Classical conditioning, which was first illustrated by Ivan Pavlov, explains how a neutral stimulus can, through association with an unconditioned stimulus, produce a conditioned response. This model explains behaviors like phobias and certain emotional reactions, such as the case of when a certain sound provokes anxiety due to some past unfortunate experience. Operant conditioning, developed by B.F. Skinner, focuses on the consequence-based shaping of behavior — reinforcement of behavior, but punishment of it. Reinforcements are positive (placement of a desired stimulus) or negative (separation from an undesired one), while punishments are positive (placement of an undesired stimulus) or negative (retrieval of a desired one). This has widespread application in the modification of behavior, such as in education and parenting. Observational learning, studied by Albert Bandura in the Bobo doll experiment, proved that individuals, especially children, learn from watching others, especially when the behaviors were rewarded. Together, these theories prove that learning is a multifaceted process governed by direct experience, consequences, and social observation. Also, learning comes closely associated with memory, which stores such learned responses, and social psychology since habits are most often learned or re-performed in groups of people.