THC Editorial Team June 9, 2021
What Is Disgust?
According to the American Psychological Association, disgust is defined as a strong aversion toward a smell, touch, person, or behavior that is considered “morally repugnant” to the person experiencing disgust.1 The emotion of disgust is featured in almost every list of basic emotions, from the earliest literature in India to Charles Darwin’s The Expression of the Emotions in Man and Animals. More recently, Paul Ekman’s theory of emotions includes disgust as one of the six basic emotions of the human experience because, like the other basic emotions, it connects cognitive and physical reactions.2
Some researchers posit an evolutionary basis for disgust. Behavioral scientist Valerie Curtis has argued that disgust evolved in humans as an avoidance mechanism for infectious diseases. For example, people who contract pandemic flu and experience revulsion toward symptoms such as diarrhea might practice better hygiene in the future and thus decrease the chance of disease spread.3
Other scientists recognize both the biological and social roots of disgust and have formed theories that combine the two. For example, psychologist Paul Rozin at the University of Pennsylvania has used evolutionary biologist Ernst Mayr’s theory of preadaptation, which states that something may evolve for one purpose but later serve another, to describe disgust. In particular, Rozin has argued that disgust initially evolved among humans as a physical response to disagreeable tastes, primarily to shield against foods that could be harmful, such as poisonous or spoiled foods, but has since become synonymous with emotional responses that occur when a person’s moral code is undermined by the actions of others.4 According to this framework, disgust toward certain foods is considered an innate aspect of human experience, but the emotional dimensions of disgust are thought to be acquired culturally.4
The difference between what cultures consider disgusting is notable. For example, it is not custom for people to take off their shoes in America when they enter a home. However, in Japan, taking off one’s shoes before entering a home is a common procedure because it would be considered disgusting to bring the dirt from the outside world into the home.4
Although disgust may be evolutionarily beneficial, it can also prompt adverse outcomes. Socially, for example, disgust underpins certain types of prejudice among humans—racism, sexism, and homophobia all involve repugnance toward a group of people.5 On an individual level, researchers have observed that disgust plays a central role in many mental health conditions and disorders such as phobias, eating disorders, posttraumatic stress disorder, and obsessive-compulsive disorder.3,4
Triggers for Disgust
When examining the triggers for disgust, the underlying adaptive nature of disgust reveals itself. Consider disgust’s role in disease avoidance. People are often disgusted by the common symptoms of diseases, such as gagging, vomiting, sweating, coughing, and visible sores. The smells, sights, textures, and tastes of spoiled foods also tend to elicit a disgust response.6
How Disgust Physically Manifests
While disgust has evolved to include repulsion toward actions that violate a person’s moral code, its physical expressions have remained mainly the same.4 Common examples of the physical manifestations of disgust include aspects of physiology, behavior, facial expressions, and body expressions:4
- Sensitivity to contamination7
- Agape mouth
- Extension of tongue
- Wrinkling of nose or eyebrows
- Raised upper lip8
- Turning of head or body away from the object of disgust
- Covering of nose and mouth
Disgust and Mental Health
Although disgust might have first evolved for beneficial reasons, it can also have downsides—particularly when it is extreme, occurs in inappropriate circumstances, or interrupts daily functioning.4 More recently, researchers have labeled disgust as a key feature of several mental health conditions.
Disgust in Obsessive-Compulsive Disorder (OCD)
Several studies support the idea that some types of OCD are viewed as disorders of the disgust system. Specifically, 50% of people with OCD exhibit issues with contamination as a central component of their OCD experience.3 These contamination issues can be fixations on things such as diseases, bacteria, bodily fluids, or insects being spread to items surrounding a person with OCD. It is important to note that these people specifically describe their issues with contamination as a matter of disgust rather than fear.3 People with OCD toward contamination often deal with intrusive thoughts about impurity and perform ritualistic and excessive sanitation of themselves and their environment in an attempt to ease their stress.3 In one study, researchers orchestrated a sequence in which a pencil touched a toilet bowl and then was rubbed on another pencil that was rubbed on another pencil, and so forth. Whereas healthy participants reported a lack of concern with contamination by the fourth pencil, participants with OCD were distressed about contamination past the 10th pencil.9
Disgust in Phobias
For many years, phobias were considered to be primarily fear based; however, in recent years, certain phobias, especially those involving nonpredatory animals such as spiders or rats and blood-injection-injury (BII) phobia, are viewed as predominately disgust based.3 While people with a spider phobia may be fearful about a bite from a spider, they tend to be predominately concerned with the spider’s unpleasant physicality, dirtiness, and potential for being a disease carrier.3 Particularly, certain traits in animals, like hairiness or sliminess, can evoke feelings of disgust and avoidant behavior.10 The evidence for disgust as a key player in BII phobia is even stronger. BII phobia involves avoidance of the sight of blood, whether in injuries or medical procedures. People suffering from BII phobia commonly report disgust and physical manifestations of disgust more than they report any fear of BII.10
Disgust in Eating Disorders
Many studies reveal that disgust plays a key role in the development and maintenance of eating disorders. Those who suffer from eating disorders may view food, their body, and/or their bodily functions as objects of disgust. Considering food’s qualities and the sources they come from through a lens of disgust promotes eating disorder behaviors of restriction, avoidance, or purging. Disgust toward one’s body and the act of purging is also a vehicle for enabling eating disorders.3
In one paper published in 1998, Graham Davey and colleagues investigated the relationship between disgust sensitivity and eating disorders across two studies. The first study revealed a significant positive correlation between disgust sensitivity measures and eating disorder measures; however, this was found in females only. The second study revealed that participants who were clinically diagnosed with an eating disorder reported far higher levels of disgust than healthy subjects.11 In another study published in 2017, researchers at De Montfort University gave an online questionnaire to 592 women with diagnosed anorexia nervosa or bulimia nervosa or no history of an eating disorder. Participants suffering from an eating disorder reported far higher ratings of self-disgust than those without an eating disorder history.12
Disgust in Posttraumatic Stress Disorder (PTSD)
There is growing evidence that PTSD involves disgust. Research has found that trauma-inducing incidents can trigger disgust as an adapted response to harmful situations.3 Professor of psychology at Vanderbilt University Bunmi Olatunji and colleagues published a study in 2008 that investigated the aspect of mental pollution, such as feelings of dirtiness, in sexual assault victims with PTSD. In a pool of 48 participants, Olatunji found that mental pollution, or feeling dirty despite lack of physical contact, was positively correlated with PTSD symptoms.13 In another study published in 2017, researchers at universities in Kentucky, Arkansas, and Oklahoma sought to determine how self-disgust is involved in PTSD and suicide risk. Researchers supplied 347 people who had been exposed to trauma with a questionnaire to assess their PTSD symptoms, depressive symptoms, suicidality, and self-disgust. The researchers found that PTSD symptoms were positively correlated with suicide risk due to self-disgust toward one’s body or self-concept, but not self-disgust toward their behaviors.1
Neurological Processes in Disgust
Researchers have found evidence that the emotion of disgust plays a critical role in some mental health conditions through behavioral studies and neurological studies. Specifically, research has found the insular cortex, amygdala, and basal ganglia in disgust function/dysfunction.
Neuroimaging studies and brain injury research reveal that the insular cortex, which is involved in homeostatic functions and the parasympathetic nervous system, is a player in the facial expressions of disgust. The involvement of the insular cortex could also explain the deceleration of the heart that can occur during disgust.9,15
There is also evidence that the striatum within the basal ganglia, which is involved in voluntary movement, is also involved in the emotion of disgust. Studies using disgust-provoking photographs and studies that ask subjects to recall disgusting events have shown significant involvement of the basal ganglia.9 Another study examined subjects with Huntington’s disease and carriers of Huntington’s disease, a disease that involves poor function of the striatum. Interestingly, these individuals could not recognize the facial expressions of disgust but had no issues recognizing facial expressions of other emotions.4,9
Studies have indicated that exercises in self-affirmation of kindness and reappraisal (reassessing one’s feelings) can help people reduce levels of disgust. Research published in 2015 explored the effect of self-affirmation of kindness in regulating disgust toward one’s physical appearance. Fifty-six participants were randomly assigned to either a group that answered a questionnaire to self-affirm kindness or a control group that did not. Then, all participants rated their negative feelings (including disgust) toward their appearance and behavior. Those who self-affirmed their kindness felt less disgust toward their appearance than those who did not.16 Thus, self- affirmation of kindness may be a worthy exercise to combat feelings of disgust related to body image, which could be especially important for individuals with eating disorders.
Another study conducted by Olatunji and colleagues published in 2015 examined the impact of emotion regulation exercises like reappraisal and suppression on the emotions of disgust and fear. Ninety-five individuals were shown a video to induce either disgust or fear and were asked to either reappraise or suppress their responses to the videos. For the people who were shown the fear-inducing video, suppression and reappraisal were not significantly different in their abilities to reduce distress. Yet, those who employed reappraisal during the disgust-provoking videos showed substantially less distress than those who used suppression.17 Thus, reappraisal may be a helpful strategy to self-regulate disgust.