the return of a response to an extinguished conditioned stimulus due to exposure to an unconditioned stimulus. For example, a person who gets a headache from using earbuds may develop an aversion to using them. This aversion may become extinguished after the person tries using earbuds again a few times without getting a headache. However, if the person then gets a headache (for any reason), the aversive response to using earbuds may return (or be reinstated).