Final answer:
The example illustrates the phenomenon of spontaneous recovery in classical conditioning. After a rest period, the previously extinguished conditioned response reappears.
Step-by-step explanation:
The phenomenon illustrated in the example is spontaneous recovery. In classical conditioning, spontaneous recovery refers to the reappearance of a previously extinguished conditioned response after a period of rest or time without further conditioning trials.
In this scenario, the dog had successfully learned to associate the sound of the bell with the arrival of food, leading to salivation. However, after a period of time without the bell-food pairing, the dog spontaneously started salivating again when it heard the bell, indicating that the original conditioned response was not completely extinguished.
This suggests that the learning was not completely erased during the extinction phase and can still resurface under certain conditions, such as a rest period, leading to the reappearance of the conditioned response.