Ivan Pavlov
(born September 26, 1849 - died February 27, 1936)
is a Russian physiologist known chiefly for his development of the concept of the conditioned reflex. In a now-classic experiment, he trained a hungry dog to salivate at the sound of a metronome or buzzer, which was previously associated with the sight of food. He developed a similar conceptual approach, emphasizing the importance of conditioning, in his pioneering studies relating human behaviour to the nervous system.
(source: www.britannica.com)