Learning theories study about classical conditioning.
Results - forward/ backward pairing
Results - extinction/ spontaneous recovery
NS initially didn't create a response, but the UCS elicited immediate salivation. After forward pairings of NS & UCS = NS typically elicited salivation, after being presented for a few seconds. Backwards pairing = recorded no response to the NS. Pavlov noted the salivation reflex only became associated with the NS if the dog was alert and not distracted.
Extinction of salivation could be seen as the salivary volume decreased after repeated presentation of the CS without the UCS. The response to the CS spontaneously recovered on some occasions.
In the brain a link is likely to be made between a UCS and an NS that occurs just before the UCS. Pavlov called this signalisation which has survival value in preparing organisms for events. This idea can be linked to the experiment, as the dogs got prepared to eat by learning to salivate at the sound of the buzzer.