Long after her conditioned fear of dogs had been extinguished, marcy experienced an unexpected surge of nervousness when she first met her cousin's new cocker cocker spanielspaniel. her unexpected nervousness best illustrates:

This is a good example of Spontaneous Recovery. The Spontaneous Recovery occurs when we learn a behavior, in this case, fear the dogs, then learned not to fear, producing a process known as the extinction of behavior. But when the behavior reappears spontaneous recovery occurs, that is, fear of dogs reappears.

I hope my answer can help you.