He was a Russian physiologist, psychologist, and physician, who was awarded the Nobel Prize in Physiology or Medicine in 1904 for research pertaining to the digestive system.
He thereby established the basic laws for the establishment and extinction of what he called "conditional reflexes" – i.e., reflex responses, like salivation, that only occurred conditionally upon specific previous experiences of the animal.
Pavlov was a dexterous operator who was compulsive about his working hours and habits. He would sit down to lunch at exactly 12 o'clock, he would go to bed at exactly the same time each evening and he would always leave Leningrad for Estonia on vacation on the same day each year. This behavior changed when his son Victor died in the White Army – after which he suffered from insomnia.
Unlike many pre-revolutionary scientists, Pavlov was highly regarded by the Soviet government, and he was able to continue his researches until he reached a considerable age. Pavlov himself was not favorable towards Marxism, but as a Nobel laureate he was seen as a valuable political asset.
Pavlov contributed to many areas of physiology, neurology and psychology.
Most of his work involved research in temperament, conditioning and involuntary reflex actions.