Ivan Pavlov mostly belonged to the school of thought called behavioralism. He studied classic conditioning and researched physiology and digestion. He lived from 1849 to 1936. He is known for his famous experiment where he put tubes in a dogs mouth and noticed their mouth involuntarily salivated when given meat powder. He then rang a bell everytime he gave the dog the meat powder. After a while he realized if he rang the bell the dog would salivate with or without the meat powder, creating Classic Conditioning.