Our emotional reactions, including not only fear but love, hate, and disgust, are largely learned, and they are learned mainly through Pavlovian conditioning. Relatively few stimuli can arise fear or other strong emotional reactions, but objects that are paired with emotion arousing items will soon come to elicit those emotions as well.

The use of Pavlovian procedures to reverse the unwanted effects of conditioning. Because the person is gradually exposed to the fearful stimulus, this kind of therapy is now often called exposure therapy. Ex. Peter's fear of rabbits which was a CS and how pairing a positive US (crackers) with it helped him unlearn his CS fear of rabbits.

Barbara Rothbaum and colleagues conducted the first controlled experiment using VRET to treat phobias. Treatment involves exposing the subjects to low-level fearful stimuli in the absence of any real danger.  

Result from the pairing of distinctive flavors and aversive (especially nausea-inducing) stimuli. Whereas the CS and US must normally appear close together for conditioning to be effective, taste aversions often occur even when the US is delayed for an hour or more.

Utilized for treatment of paraphilia. A CS that elicits inappropriate sexual arousal is paried with a US that elicits an unpleasant response (often nausea). When such therapy is effective the stimuli that once elicited sexual arousal no longer do so and may even elicit feelings of anxiety and discomfort.