Pavlov's Classical Conditioning Experiments

Beginning in the 1890s, the Russian physiologist Ivan Pavlov, originally studying the digestive systems of dogs, noticed that his laboratory dogs had begun salivating at the sound of a technician's footsteps before food was even presented, and he redirected his research to systematically investigate the phenomenon. By repeatedly pairing a neutral stimulus, such as the sound of a metronome or bell, with the presentation of food, Pavlov showed that dogs could learn to salivate in response to the neutral stimulus alone, a learned association he called a conditioned reflex. The work, for which Pavlov received the 1904 Nobel Prize in Physiology or Medicine (awarded for his earlier digestive research rather than conditioning itself), established classical conditioning as a foundational concept in the scientific study of learning and behavior, and shaped the subsequent development of behaviorist psychology.