Ivan Petrovich Pavlov's research on mammalian digestion earned him the Nobel Prize and his research regarding conditioned reflexes brought him international recognition. The colloquial expression "Pavlov's dog" refers to Pavlov's famous experiments in which he taught a dog to salivate at the sound of a bell by associating the bell with feeding. This research helped spawn a physiologically oriented school of psychology that focused on the influence of conditioned reflexes on learning and behavior. Because of his contribution to the fields of psychology and physiology, Pavlov became one of Russia's most revered scientists in his day--even tolerated by the communist Soviet regime, of which he was openly critical.

Pavlov was born in Ryazan, Central Russia, on September 26, 1849. His father, Pyotr Dmitrievich Pavlov, was a priest who rose through the ranks and eventually headed one of the most influential parishes in the area. A devoted reader and scholar, Pyotr...