Desensitization (psychology)

In psychology, Desensitization is a treatment or process that diminishes emotional responsiveness to a negative, aversive, or positive stimulus after repeated exposure. Desensitization can also occur when an emotional response is repeatedly evoked when the action tendency associated with the emotion proves irrelevant or unnecessary. The process of desensitization was developed by psychologist Mary Cover Jones and is primarily used to assist individuals in unlearning phobias[1] and anxieties.[2][3][4] Desensitization is a psychological process where a response is repeatedly elicited in circumstances where the emotion's propensity for action is irrelevant.[5] Joseph Wolpe (1958) developed a method of a hierarchal list of anxiety-evoking stimuli in order of intensity, which allows individuals to undergo adaptation. Although medication is available for individuals with anxiety, fear, or phobias, empirical evidence supports desensitization with high rates of cure, particularly in clients with depression or schizophrenia.[6] Wolpe's "reciprocal inhibition" desensitization process is based on well-known psychology theories such as Hull's "drive-reduction" theory and Sherrington's concept of "reciprocal inhibition."[7] Individuals are gradually exposed to anxiety triggers while using relaxation techniques to reduce anxiety.[7] It is an effective treatment for anxiety disorders.[7]

Desensitization
MeSHD003887

Steps

The hierarchical list is constructed between client and therapist in an ordered series of steps from the least disturbing to the most alarming fears or phobias. The therapist and the patient for acrophobia create a list of escalating exposure scenarios.[8] The patient progresses from using a low step ladder to standing and taking the first step.[8] The scenes are arranged in a commonly used version of this treatment to increase arousal.[8] Secondly, the client is taught techniques that produce deep relaxation. This is repeated until the hierarchy element no longer causes anxiety or fear, at which point the next scene is shown.[8] This procedure is repeated until the client has finished the hierarchy.[8] It is impossible to feel both anxiety and relaxation simultaneously, so easing the client into deep relaxation helps inhibit any anxiety. Systematic desensitization (a guided reduction in fear, anxiety, or aversion[9]) can then be achieved by gradually approaching the feared stimulus while maintaining relaxation. Desensitization works best when individuals are directly exposed to the stimuli and situations they fear, so anxiety-evoking stimuli are paired with inhibitory responses. This is done either by clients performing in real-life situations (vivo desensitization) or, if it is not practical to directly act out the steps of hierarchy, by observing models performing the feared behaviour (known as vicarious desensitization). Clients slowly move up the hierarchy, repeating performances if necessary, until the last item on the list is performed without fear or anxiety.[10] According to research, it is not necessary for the hierarchy of scenes to be presented in a specific order, nor is it essential for the client to have mastered a relaxation response.[8] Recent research suggests that none of the three conditions listed above are required for successful desensitization when taken as a whole.[11] The only prerequisite appears to be the ability to imagine frightening scenes, which need not be ordered in a particular order or lead to the relaxation of the muscles.[11]

Suggested mechanisms

Reciprocal Inhibition

Reciprocal inhibition is based on the idea that two opposing mental states cannot coexist and is used as both a psychological and biological mechanism.[12] The theory that "two opposing states cannot occur simultaneously" i.e. relaxation methods that are involved with desensitization inhibit feelings of anxiety that come with being exposed to phobic stimuli.[12] Deep muscle relaxation techniques are the primary method used by Wolpe to increase parasympathetic nervous system activity, the nervous system the body uses to relax.[12]

According to Tryon (2005), being relaxed does not always imply being anxious, and it is critical to avoid tautology when discussing reciprocal inhibition.[12] This phenomenon is only observed when two events have a strong negative correlation.[12] Reflex research has revealed the biological basis of reciprocal inhibition, which occurs when a tap on the patellar tendon results in muscle relaxation (inhibition) of the flexors and muscle activation (excitation) of the extensors.[12] This is an example of coordinated inhibition and excitation in different muscles.[12]

One criticism is that reciprocal inhibition isn't a necessary part of the process of desensitizing people as other therapies that are along similar lines, such as flooding, work without pre-emptive, inhibitory relaxation techniques.[12] A review of empirical evidence confirmed that therapy without relaxation was equally effective and gave birth to exposure therapy.[12]

A review of Taylor's (2002) classification of reciprocal inhibition as being short-term but with long-term effects within the understanding of desensitization doesn't make sense due to it being theoretically similar to reactive inhibition, which is longer-term as it develops conditioned inhibition.[12]

Counterconditioning

Counterconditioning suggests that the anxiety response is replaced by a relaxation response through conditioning during the desensitization process.[12] Counterconditioning is the behavioural equivalent of reciprocal inhibition which is understood as a neurological process.[12] Wolpe (1958) used this mechanism to explain the long-term effects of systematic desensitization as it reduces avoidance responses and therefore excessive avoidance behaviours contributing to anxiety disorders.[12] However, this explanation is not supported by empirical evidence.[12][13]

For similar reasons to reciprocal inhibition, counterconditioning is criticized as the underpinning mechanism for desensitization due to therapies that don't suggest a replacement emotion for anxiety being effective in desensitizing people.[12] It is to be noted that there would be no behavioural difference if reciprocal inhibition or counterconditioning were the functioning mechanisms.[13]

Habituation

This theory explains that with increased exposure to stimulus there will be a decreased response from the phobic subject. There is empirical evidence to suggest that overall phobia responses are reduced in people who have specific phobias with in vivo exposure. However, empirical evidence does not support habituation as an explanation of desensitization due to its reversible and short-term nature.[12]

Extinction

Phobic responses are decreased after exposure to stimuli without avoidance and with a lack of reinforcement. However, this cannot be used to explain why desensitization works, as it solely describes the functional relationship between absent reinforcement and phobic responses and lacks an actual mechanism for why such a relationship exists.[12]

Wolpe disagreed that extinction could be the explanatory mechanism of how desensitization occurs with therapies based on exposure, as he believed that repeated exposure was insufficient and had likely already happened during the lives of people with specific phobia's lives.[12]

Two-Factor Model

Exposure to phobic stimuli and then a subsequent avoidance response may strengthen the future anxiety as the avoidance response reduces the stress which therefore reinforces the avoidant behaviour (prominent feature of specific phobias and anxiety disorders).[14][12] Therefore, exposure with non-avoidance is seen as essential in the desensitization process.

Self-Efficacy

This is the view that a person's belief in themselves of being able to cope increases, especially when moving up the exposure hierarchy and having confirmatory experiences of coping from the lower levels.[12] The increase in self-efficacy then explains fear reduction i.e. desensitization to stimuli.[12]

This mechanism as an explanation for desensitization lacks an explanation for how increased expectation of fear reduction leads to reduced fear responses and how if a person didn't experience a reduced fear response whether desensitization will have occurred as their anxiety response will reaffirm their phobia.[12]

Expectancy Theory

This theory suggests that because people expect that the therapy is going to work and change their view on how they are going to receive the phobic stimuli after speaking with the therapist, their responses will align with that and display reduced anxiety[12][15] Marcia et al. (1969) found that those with high expectancy change (receiving full expectancy treatment) had comparable results to those who had systematic desensitization therapy suggesting its just a change in expectancy that reduces fear responses.[15]

Emotional Processing Theory

R.J McNally explains, "fear is represented in memory as a network comprising stimulus propositions that express information about feared cues, response propositions that express information about behavioural and physiologic responses to these cues, and meaning propositions that elaborate on the significance of other elements in the fear structure".[16] Excessive fear such as phobias can be understood as a problem in this structure which lead to problems processing information leading to exaggerated fear responses.[16] Using this information about fear networks, desensitization can be achieved accessing the fear network using matching stimuli to information in the fear network and then having the person engage with the stimuli to input new information into the network by disconfirming existing propositions.[16]

Neuroscience

Medial Prefrontal Cortex

The medial prefrontal cortex works with the amygdala,; when damaged, a phobic subject finds desensitization more difficult.[16] Neurons in this area aren't fired during the desensitization process despite reducing spontaneous fear responses when artificially fired, suggesting the area stores extinction memories that reduce phobic responses to future stimuli related to the phobia (conditioned), which explains the long-term impact of desensitization.[16]

N-methyl-D-aspartate Glutamatergic Receptors

NMDA receptors have been found to play a key role in the extinction of fear and therefore, the use of an agonist would accelerate the reduction in fear responses during the process of desensitization.[16]

Self-control Desensitization

Self-control desensitisation is a variant of systematic desensitisation, which Joseph Wolpe pioneered.[17] Instead of using a passive counter-conditioning model, it uses an active, mediational, coping skills change model.[17] It uses coping mechanisms like relaxation as an alternative to an anxiety response when anxiety-inducing stimuli are present.[17] In-person practise in actual anxiety-producing situations is encouraged.[17] In many ways, it is comparable to other methods for controlling anxiety, like applied relaxation and anxiety management training.[17] During self-control desensitisation, clients are given a justification that is primarily coping skills oriented in nature.[17] They are told that they have learned to react to certain situations by becoming anxious, tense, or nervous based on previous experience.[17] Then it is explained to them that they will learn new coping skills to swap out their unfavorable reactions for more flexible ones.[17] They are instructed to use relaxation techniques and other coping mechanisms in a hierarchy of anxiety-producing situations to reduce tensions and serve as covert rehearsal for eventualities. These techniques include breathing control, attention to internal sensations, and relaxation techniques.[17] According to research, self-control desensitisation is effective for various anxiety disorders but is not more effective than other cognitive or behavioural techniques.[17]

Criticism and Developments

With the widespread research and development of behavioural therapies and experiments being conducted in order to understand the mechanisms driving desensitization, a consensus often arises that exposure is the key element of desensitization.[12][16] This suggests the steps leading up to the actual exposure such as relaxation techniques and the development of an exposure hierarchy are redundant steps for effective desensitization.[12][16] It would seem that crucial elements for a successful therapeutic outcome in both desensitisation and more conventional forms of psychotherapy are the cognitive and social aspects of the therapeutic situation.[11] These factors include the expectation of therapeutic benefit, the therapist's ability to foster social reinforcement, the information-feedback of approximations towards successful fear reduction, training in attention control, and the vicarious learning of contingencies of non-avoidance behaviour in the fear situation (via instructed imagination).[11]

Effects on animals
Horses have a natural fear of unpredictable movement. Pictured is a horse being desensitized to accept the fluttering skirt of a lady's riding habit.
Main article: Sacking out

Animals can also be desensitized to their rational or irrational fears. A race horse who fears the starting gate can be desensitized to the fearful elements (the creak of the gate, the starting bell, the enclosed space) one at a time, in small doses or at a distance. Clay et al. (2009) conducted an experiment whereby he allocated rhesus macaques to either a desensitization group or a control group, finding that those in the desensitization group showed a significant reduction in both the rate and duration of fearful behavior. This supports the use of PRT training. Desensitization is commonly used with simple phobias like insect phobia.[18][19] In addition, desensitization therapy is a useful tool in training domesticated dogs.[20] Systematic desensitization used in conjunction with counter-conditioning was shown to reduce problem behaviours in dogs, such as vocalization and property destruction.[20]

Effects on violence

Desensitization also refers to the potential for reduced responsiveness to actual violence caused by exposure to violence in the media. However, this topic is debated in the scientific literature.[21] Desensitization may arise from different media sources, including TV, video games, and movies. Some scholars suggest that violence may prime thoughts of hostility, possibly affecting how we perceive others and interpret their actions.[22][23][24] Desensitization has been shown to lower arousal to violent scenes in heavy versus light television viewers at the physiological level.[25] It has frequently been suggested that those who commit extreme violence have blunted sensibilities as a result of watching violent videos repeatedly.[25] Desensitization to violence has been linked to a number of outcomes.[5] It has been observed, for example, as less arousal and emotional disturbance when witnessing violence, as greater hesitancy to call an adult to intervene in a witnessed physical altercation, and as less sympathy for victims of domestic abuse.[5] Recent school shootings have sparked a lot of discussion about the desensitising effects of violent video games and the possible involvement of "shooter" games, which teach gun handling skills and provide intense desensitisation training.[5]

It is hypothesized that initial exposure to violence in the media may produce a number of aversive responses, such as increased heart rate, fear, discomfort, perspiration, and disgust. However, prolonged and repeated exposure to violence in the media may reduce or habituate the initial psychological impact until violent images do not elicit these negative responses. Eventually, the observer may become emotionally and cognitively desensitized to media violence. In one experiment, participants who played violent video games showed lower heart rate and galvanic skin response readings, which the authors interpreted as displaying physiological desensitization to violence.[26] However, other studies have failed to replicate this finding.[27][28] Some scholars have questioned whether becoming desensitized to media violence specifically transfers to becoming desensitized to real-life violence.[29] In addition, psychological research frequently focuses on how members of a group behave, and these studies demonstrate that media violence raises the likelihood that members of the group will become desensitised and act aggressively.[30] However, more sensitive developmental studies might find that this effect can be moderated by some individual difference variables (such as empathy, perspective taking, or trait hostility).[30]

See also

References
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