extinction- when Pavlov stopped giving dog food after the sound of the metronome, the dog stopped salivating at the sound. the conditioned response can briefly reappear when the original CS returns, although the response is usually weak and short lived.
By repeatedly giving food immediately following the sound of the bell, those dogs came to associate the sound with feeding time. As such, the dogs would begin to salivate even if the food did not come.
Food is the Unconditioned Stimulus (US). This means that the food causes the response of salivation without previous learning. Bell is the Conditioned Stimulus (CS). This is the stimulus which is paried with the food to make the dog eventually salivate to just the sound of the bell alone.
Pavlov found that for associations to be made, the two stimuli had to be presented close together in time (such as a bell). He called this the law of temporal contiguity.
Pavlov wondered if hunger could trigger their former conditioning. He starved his dogs for three days. It didn't work. “During three days while the animal was purposely left without food its general behaviour during the experiments remained unaltered,” he wrote.
Pavlov's aim was to use the salivary conditioning method to investigate the function of the brain of higher animals in their adaptation to the external environment.