How did Ivan Pavlov demonstrate classical conditioning in dogs?

Ivan Pavlov demonstrated classical conditioning by systematically pairing a neutral stimulus with a stimulus that naturally triggered a biological response.12

In his experiments, a hungry dog was restrained in a harness. Pavlov used food powder as an unconditioned stimulus, which naturally elicited salivation, known as the unconditioned response. He then introduced a neutral stimulus—such as the sound of a metronome, buzzer, or bell—immediately before providing the food.123

After repeated trials, the dog learned to associate the sound with the arrival of food. Eventually, the sound alone became a conditioned stimulus, capable of triggering salivation even in the absence of food. This learned behavior is called a conditioned response. If the sound was presented repeatedly without the food, the conditioned response would gradually disappear, a process known as extinction.21