Pavlov, Ivan Petrovich (1849–1936)
Russian physiologist best known for his work on the conditioned
reflex. Regularly, over long periods, Pavlov rang a bell just before feeding
dogs, and found that eventually they salivated on hearing the bell, even
when there is no food forthcoming. He also studied the physiology of the
digestive system, and for this
he received the 1904 Nobel Prize in Physiology or Medicine.