Specific phobias are one class of mental illness often treated through the behavior therapy or cognitive-behavioral process of systematic desensitization. When individuals possess irrational fears of an object, such as height, dogs, snakes, and close spaces, they tend to avoid it. Since escaping from the phobic object reduces their anxiety, patients’ behavior to reduce fear is reinforced through negative reinforcement, a concept defined in operant conditioning. The goal of Systematic Desensitization is to overcome this avoidance pattern by gradually exposing patients to the phobic object until it can be tolerated. This will be challenging for the patient at first to deal with the fear, but gradually, most will overcome this fear. In classical and operant conditioning terms the elicitation of the fear response is extinguished to the stimulus (or class of stimuli).