A dog salivating at a bell revealed how the brain learns to associate

While studying digestion, Ivan Pavlov noticed his dogs began salivating before food even arrived, just at the sound of an assistant's footsteps. He showed the brain could link an unrelated signal, like a bell, to an automatic reflex through repeated pairing, founding the science of classical conditioning.

— Ivan Pavlov, Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex — Oxford University Press, 1927 (trans. G. V. Anrep)
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