How does extinction occur in Pavlovian conditioning?

In Pavlovian conditioning, also known as classical conditioning, extinction is the process of reducing or eliminating a conditioned response by repeatedly presenting the conditioned stimulus without the unconditioned stimulus that originally reinforced it.12

For example, in the experiments conducted by the Russian physiologist Ivan Pavlov, a dog learns to salivate (the conditioned response) in anticipation of food (the unconditioned stimulus) when it hears a bell (the conditioned stimulus). Extinction occurs when the bell is sounded repeatedly during test trials without being followed by the delivery of food powder. As the reinforcement is withheld, the strength of the conditioned response—measured by the amount of saliva secreted—gradually diminishes.12

It is important to note that while the response is extinguished, it may still be subject to spontaneous recovery, which is the reappearance of the conditioned response after a period of time without further positive reinforcement.3