Ivan Pavlov was born on September 14, 1849 in Ryazan, Russia. His father, Peter Dmitrievich Pavlov, was the village's priest. He spent his youth studying at the local church's school.

After primary school, Ivan decided to go to seminary school to become a priest, but later dropped out. Instead of studying theology, he decided that he wanted to study the natural sciences and enrolled at St. Petersburg University in 1870. In his free time, he worked as a researcher for Dr. Botkin, a famous Russian physician. In 1883, he completed his doctoral thesis on the subject of nerves surrounding the heart. He proposed that the heart's rhythm was a reflex in response to stimulation by the nervous system.

In 1881, Pavlov married a woman named Seraphima Vasilievna Karchevskaya, who was a teacher. Their first pregnancy ended up being a miscarriage, but they later had a son named Wirchik, who unfortunately died at a young age. Later, they had three more sons: Vladimir, Victor, and Vsevolod, as well as a daughter named Vera.

In 1890, Pavlov was made director of the Institute of Experimental Medicine's Department of Physiology. He would continue to hold this position for the next 45 years, until his death. That year, he was also appointed Professor of Pharmacology at the Military Medical Academy. In 1895, he was appointed Chair of Physiology at the Military Medical Academy.

Pavlov's most impressive research involved the behavior of animals and psychology. His original intent was to analyze the saliva produced by dogs when different types of food were fed to them. However, he noticed that the dogs began to salivate before the food entered their mouths and decided to study the triggers of salivation. He termed the salivation prior to eating "psychic secretion" in his early scientific journals.

Pavlov decided to see if he could make the dogs salivate with any sort of stimulus and was shocked by the results. By creating a type of visual or auditory stimulus just before feeding the dogs on several occasions, he discovered that they began salivating after observing the stimulus, even when no food was visible. From this behavior, he determined that animals, such as dogs, developed "conditional reflexes" based on prior experiences. In this case, the dogs had a conditional reflex of salivation based on the prior stimulus being associated with food.

Pavlov's psychology studies also focused on the reflexes that occur in response to stress and pain. Pavlov also performed the first studies on transmarginal inhibition, a phenomenon where the body shuts down in the face of extreme stress and/or pain. He classified four types of human temperaments: plegmatic, choleric, sanguine, and melancholic.

In the 1890s, Pavlov also performed extensive research regarding digestion in animals. In his experiments, he tried removing parts of the digestive system to see how it would change the digestive process. He also tried disabling nerves that led to the digestive system and extracting the contents of the stomach and intestines during digestion. His research in digestion led to a nomination for the 1904 Nobel Prize in Physiology and Medicine, which he ended up winning.

Pavlov's personal life was very uniform and organized to the point of being compulsive. He took lunch precisely at noon every day, fed his dogs at the same time every day, and went to bed at the same time every night. Every year, he would also take vacations on the exact same day.

Ivan Pavlov died in the city of Leningrad on February 27, 1936 from natural causes. You can still visit his laboratory in the city of St. Petersburg since it has been turned into a museum.