After Pavlov's dogs became conditioned to salivate at the sound of the metronome, he experimented with sounding the metronome and then failing to present the dogs with any food right away. Soon they stopped salivating to the sound of the metronome.
This represents the process called __________.

A. extinction.
B. acquisition.
C. testing.
D. extinction.
E. spontaneous recovery.

At first, there is an unconditioned stimulus that triggers a natural response by itself, this natural response is called the unconditioned response.

Then, a neutral stimulus that doesn't produce a natural response is paired with the unconditioned stimulus by presenting them both at the same time. After some repetitions, the stimuli are paired in our mind and the behavior will take place in presence of the neutral stimulus. At this moment, the neutral stimulus is called the conditioned stimulus and it will trigger a response that is called the conditioned response.

However, sometimes this conditioned response can begin to fade, this process is called extinction and it usually happens when we present the conditioned stimulus without the presence of the unconditioned stimulus. This makes the pairing to stop happening and the behavior stops.

In this example, after the dogs became conditioned to salivate at the sound of the metronome (conditioned stimulus) he stared to sound the metronome without presenting food (unconditioned stimulus) to the dogs, so the dogs stopped salivating. Therefore, this is an example of extinction.