Although he was a brilliant physiologist and a skillful surgeon, Ivan Pavlov is remembered primarily for his development of the concept of conditioned reflex. In a well-known experiment he trained a hungry dog to salivate at the sound of a bell. The bell had previously become associated by the dog with the sight of food. Pavlov's work laid a foundation for the scientific analysis of human behavior. In 1904 he was awarded the Nobel prize for physiology or medicine for his work on digestive secretions.