Physiologists Ivan Pavlov (right) and Leovon Orbeli photographed in 1935. Ivan Petrovich Pavlov (1849-1936) was a Russian psychologist and physiologist. His most famous work was on the reflex actions in animals, notably the idea of conditioning of reflexes by repeated reward or punishment stimuli. Pavlov won the 1904 Nobel Prize for Physiology or Medicine. Levon Abragovich Orbeli (1882-1958) was an Armenian physiologist who laid the foundations of evolutionary physiology.
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