Imaginal or In Vivo Exposure and Desensitization

Systematic desensitization is a form of exposure treatment. Exposure treatments are based on the principle that clients are best treated by exposure to the very thing they want to avoid: the stimulus that evokes intense fear, anxiety, or other painful emotions. Mowrer (1947) used a two-factor theory of learning, based on animal studies, to explain how avoidance conditioning works. First, he explained that animals originally learn to fear a particular stimulus through classical conditioning. For example, a dog may learn to fear its owner’s voice when the owner yells due to the discovery of an unwelcome pile on the living room carpet. Then, if the dog remains in the room with its owner, fear continues to escalate.

Second, Mowrer explained that avoidance behavior is reinforced via operant conditioning. Specifically, if the dog manages to hide under the bed or dash out the front door of the house, it’s likely to experience decreased fear and anxiety. Consequently, the avoidance behavior—running away and hiding—is negatively reinforced because it relieves fear, anxiety, and discomfort. Negative reinforcement is defined as the strengthening of a behavioral response by reducing or eliminating an aversive stimulus (like fear and anxiety).

Note that exposure via systematic desensitization and the other procedures detailed hereafter are distinctively behavioral. However, the concept that psychological health is enhanced when clients face and embrace their fears is consistent with existential and Jungian theory (van Deurzen, 2010; see online Jungian chapter: Link to be set up**).

There are three ways to expose clients to their fears during systematic desensitization. First, exposure to fears can be accomplished through mental imagery. This approach can be more convenient and allows clients to complete treatment without ever leaving their therapist’s office. Second, in vivo (direct exposure to the feared stimulus) is also possible. This option can be more complex (e.g., going to a dental office to provide exposure for a client with a dental phobia), but appears to produce outcomes superior to imaginal exposure (Emmelkamp, 1994). Third, computer simulation (virtual reality) has been successfully used as a means of exposing clients to feared stimuli (Emmelkamp et al., 2001; Emmelkamp, Bruynzeel, Drost, & van der Mast, 2001).

Psychoeducation is critical to effective exposure treatment. D. Dobson and K. S. Dobson (2009) state:

A crucial element of effective exposure is the provision of a solid rationale to encourage your client to take the risks involved in this strategy. A good therapeutic alliance is absolutely essential for exposure to occur. (p. 104)

Further, D. Dobson and K. S. Dobson (2009) provide a sample client handout that helps inform clients of the exposure rationale and procedure.

Exposure treatment means gradually and systematically exposing yourself to situations that create some anxiety. You can then prove to yourself that you can handle these feared situations, as your body learns to become more comfortable. Exposure treatment is extremely important in your recovery and involves taking controlled risks. For exposure treatment to work, you should experience some anxiety—too little won’t be enough to put you in your discomfort zone so you can prove your fears wrong. Too much anxiety means that you may not pay attention to what is going on in the situation. If you are too uncomfortable, it may be hard to try the same thing again. Generally, effective exposure involves experiencing anxiety that is around 70 out of 100 on your Subjective Units of Distress Scale. Expect to feel some anxiety. As you become more comfortable with the situation, you can then move on to the next step. Exposure should be structured, planned, and predictable. It must be within your control, not anyone else’s. (p. 104)

Massed (Intensive) or Spaced (Graduated) Exposure Sessions

Behavior therapists continue to optimize methods for extinguishing fear responses. One question being examined empirically is this: Is desensitization more effective when clients are directly exposed to feared stimuli during a single prolonged session (e.g., one 3-hour session; aka massed exposure) or when they’re slowly and incrementally exposed to feared stimuli during a series of shorter sessions (such as five 1-hour sessions; aka spaced exposure)? Initially, it was thought that massed exposure might result in higher dropout rates, greater likelihood of fear relapse, and a higher client stress. However, research suggests that massed and spaced exposure desensitization strategies yield minimal differences in efficacy differences (Ost, Alm, Brandberg, & Breitholz, 2001).

Virtual Reality Exposure

Technological advancements have led to potential modifications in systematic desensitization procedures. Specifically, virtual reality exposure, a procedure wherein clients are immersed in a real-time computer-generated virtual environment, has been empirically evaluated as an alternative to imaginal or in-vivo exposure in cases of acrophobia (fear of heights), flight phobia, spider phobia, and other anxiety disorders (Krijn et al., 2007; Ruwaard, Broeksteeg, Schrieken, Emmelkamp, & Lange, 2010).

In a meta-analysis of 18 outcome studies, Powers and Emmelkamp (2008) reported a large effect size (d = 1.11) as compared to no treatment and a small effect size (d = .35) when compared to in vivo control conditions. These results suggest that virtual reality exposure may be as efficacious or even more so than in vivo exposure.

Interoceptive Exposure

Typical panic-prone individuals are highly sensitive to internal physical cues (e.g., increased heart rate, increased respiration, and dizziness). They become especially reactive when those cues are associated with environmental situations viewed as potentially causing anxiety (Story & Craske, 2008). Physical cues or sensations are then interpreted as signs of physical illness, impending death, or imminent loss of consciousness (and associated humiliation). Although specific cognitive techniques have been developed to treat clients’ tendencies to catastrophically overinterpret bodily sensations, a more behavioral technique, interoceptive exposure, has been developed to help clients learn, through exposure and practice, to deal more effectively with physical aspects of intense anxiety or panic (Lee et al., 2006; Stewart & Watt, 2008).

Interoceptive exposure is identical to other exposure techniques except that the target exposure stimuli are internal physical cues. There are at least six interoceptive exposure tasks that reliably trigger anxiety (Lee et al., 2006). They include:

  • Hyperventilation
  • Holding breath
  • Breathing through a straw
  • Spinning in circles
  • Shaking head
  • Chest breathing

Of course, before interoceptive exposure is initiated, clients receive education about body sensations, learn relaxation skills (e.g., breathing training), and learn cognitive restructuring skills. Through repeated successful exposure, clients become desensitized to previously feared physical cues (Forsyth, Fusé, & Acheson, 2009).

Response and Ritual Prevention

Mowrer’s two-factor theory suggests that, when a client avoids or escapes a feared or distressing situation or stimulus, the maladaptive avoidance behavior is negatively reinforced (i.e., when the client feels relief from the negative anxiety, fear, or distress, the avoidance or escape behavior is reinforced or strengthened; Spiegler & Guevremont, 2010). Many examples of this negative reinforcement cycle are present across the spectrum of mental disorders. For example, clients with Bulimia Nervosa who purge after eating specific “forbidden” foods are relieving themselves from the anxiety and discomfort they experience upon ingesting the foods (Agras, Schneider, Arnow, Raeburn, & Telch, 1989). Therefore, purging behavior is negatively reinforced. Similarly, when a phobic client escapes from a phobic object or situation, or when a client with obsessive-compulsive symptoms engages in a repeated washing or checking behavior, negative reinforcement of maladaptive behavior occurs (Franklin & Foa, 1998; Franklin, Ledley, & Foa, 2009; March, Franklin, Nelson, & Foa, 2001).

It follows that, to be effective, exposure-based desensitization treatment must include response prevention. With the therapist’s assistance, the client with bulimia is prevented from vomiting after ingesting a forbidden cookie, the agoraphobic client is prevented from fleeing a public place when anxiety begins to mount, and the client with Obsessive-Compulsive Disorder is prevented from washing his or her hands following exposure to a “contaminated” object. Without response or ritual prevention, the treatment may exacerbate the condition it was designed to treat. Research indicates that exposure plus response prevention can produce significant brain changes in as few as three psychotherapy sessions (Schwartz, Gulliford, Stier, & Thienemann, 2005; Schwartz, Stoessel, Baxter, Martin, & Phelps, 1996).


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