# Desensitization (psychology)

Desensitization (from Latin "de-" meaning "removal" and "sensus" meaning "feeling" or "perception") is a psychology term related to a treatment or process that diminishes emotional responsiveness to a negative or aversive stimulus after repeated exposure. This process typically occurs when an emotional response is repeatedly triggered, but the action tendency associated with the emotion proves irrelevant or unnecessary.
Psychologist Mary Cover Jones pioneered early desensitization techniques to help individuals "unlearn" (disassociate from) phobias and anxieties. Her work laid the foundation for later structured approaches to desensitization therapy, aimed at gradually reducing emotional reactions to previously distressing situations.
In 1958, Joseph Wolpe developed a ranked list of anxiety-evoking stimuli ordered by intensity to help individuals gradually adapt to their fears. Wolpe's "reciprocal inhibition" desensitization process is based on established psychology theories. These include Clark Hull's drive-reduction theory, which suggests that reducing a drive decreases anxiety, and Sherrington's concept of reciprocal inhibition, which proposes that certain responses can be inhibited by activating opposing responses.
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.

## 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. The patient progresses from using a low step ladder to standing and taking the first step. The scenes are arranged in a commonly used version of this treatment to increase arousal. 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. This procedure is repeated until the client has finished the hierarchy. 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) 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 behavior (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. 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. Recent research suggests that none of the three conditions listed above are required for successful desensitization when taken as a whole. 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.

## Suggested mechanisms
### Reciprocal inhibition

Reciprocal inhibition is based on the idea that two opposing neurological states, such as relaxation and anxiety, cannot coexist. This idea implies that methods which produce calmness by activating the parasympathetic nervous system, such as deep muscle relaxation, may reduce the responses typically associated with fear-inducing stimuli.
Critics of reciprocal inhibition point out that preparing the client with an opposing mental states is not a necessary part of the process of desensitization. For example, flooding, another technique, has also been shown to be effective.

### Counterconditioning

Counterconditioning is similar to reciprocal inhibition because both theories involve the use of relaxation to inhibit anxiety. However, while reciprocal inhibition is a neurological theory which focuses on the brain, counterconditioning is a behavioral theory which focuses on observable responses to stressors.
In the late 1950s, Wolpe used this mechanism to explain the long-term effects of systematic desensitization, as it reduces avoidance responses and therefore excessive avoidance behaviors contributing to anxiety disorders.
For reasons similar to reciprocal inhibition, the idea that counterconditioning is the fundamental mechanism for desensitization has received criticism, because there are effective therapies which do not seem to involve the use of a replacement emotion for anxiety.

### Habituation

Habituation 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.

### Extinction

Extinction is a model that demonstrates how learned behaviors decrease through the absence of anticipated reinforcement. Extinction is not only when a previously learned value lessens, but also when a new association being created leads to a new value being learned. 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.Several studies looking into the neural mechanisms of extinction propose that the amygdala is responsible for the learning and expressing of phobic responses, and also has a part in the learning and strengthening of fear extinction.
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 phobias.However, desensitization is a form of exposure therapy which in turn leads to the unwanted behavior becoming extinct due to the learned associations becoming weakened.

### 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 behavior (prominent feature of specific phobias and anxiety disorders). Therefore, exposure with non-avoidance is seen as essential in the desensitization process.

### Self-efficacy

Self-efficacy is an individual's personal assessment of their ability to successfully do something in a certain situation. 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. A high self-efficacy is shown to enhance the extinction of an unwanted behavior.
This explanation for desensitization lacks an explanation for how heightened anticipation of fear reduction leads to reduced fear responses, and it does not address whether desensitization effectively occurs if an individual does not experience decreased fear responses, potentially leading their anxiety response to reaffirm their phobia instead.

### Expectancy theory

Expectancy 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. 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.

### 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 behavioral and physiologic responses to these cues, and meaning propositions that elaborate on the significance of other elements in the fear structure". Excessive fear such as phobias can be understood as a problem in this structure which leads to problems processing information leading to exaggerated fear responses. 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.

## Neuroscience
### Medial prefrontal cortex

The medial prefrontal cortex works with the amygdala; when damaged, a phobic subject finds desensitization more difficult. 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.

### 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.

## Self-control desensitization

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

## 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. 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. 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. 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).

## Effects on animals

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. In addition, desensitization therapy is a useful tool in training domesticated dogs. Systematic desensitization used in conjunction with counter-conditioning was shown to reduce problem behaviours in dogs, such as vocalization and property destruction.

## 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. 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. Desensitization has been shown to lower arousal to violent scenes in heavy versus light television viewers at the physiological level. It has frequently been suggested that those who commit extreme violence have blunted sensibilities as a result of watching violent videos repeatedly. Desensitization to violence has been linked to a number of outcomes. 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. Recent school shootings have sparked a lot of discussion about the desensitizing effects of violent video games and the possible involvement of "shooter" games, which teach gun handling skills and provide intense desensitization training.
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. However, other studies have failed to replicate this finding. Some scholars have questioned whether becoming desensitized to media violence specifically transfers to becoming desensitized to real-life violence. 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 desensitized and act aggressively. 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).