Processing disgust is one of the most basic human functions and it has kept the species alive through the ages. Although it has been somewhat forgotten in psychology, there is already enough information available about how the brain does this.
You can define disgust as a feeling of strong dislike for certain objects or substances. It makes you want to expel it, distance yourself from it, or simply reject it.
This emotion is universal and is recognized as one of the six basic emotions found in all cultures, even in people with sensory impairments. It is accompanied by a characteristic facial expression. For example, there is an increase in the upper lip, a frown and a decrease in the corners of the mouth.
In addition, it is usually accompanied by the following phenomena:
- a decrease in voltage
- a decrease in the galvanic skin response
- an acceleration of the heart rate
- a feeling of disgust
- distance yourself from the object
- respiratory changes
- characteristic utterances, such as “Bah!”
The nature of disgust
You have to keep in mind that experience has dictated the model that the human brain adopts, both as a species and also individually. Though you may not know it, humans used to have some sort of behavioral immune system before developing the sophisticated system we have today.
This basic system used to act as a barrier protecting people from contact with parasites and other potential dangers.
The benefit derived from processing disgust is mainly related to the avoidance of disease. So while there are cultural differences about what disgusts people, the main things that trigger this emotion include:
- secretions and certain body parts, such as:
- dirty feet
- spoiled food
- critters such as insects, worms and spiders
- certain characteristics of unfamiliar people or people who are different
- violations of certain social and moral norms
This emotion is innate, but you must remember that people acquire certain aspects of that which disgusts them. This is where cultural and developmental differences become more apparent. For example, children up to the age of two do not seem to know what disgust is.
However, one could explain this by saying that they are still in the care of their parents. Mainly because the human species is quite immature and vulnerable during the first years of life. Thus, toddlers eventually develop this emotion by observing the behavior of their parents.
The brain and how it processes disgust
To understand how your brain processes disgust, you basically have to consider two areas: the insula and the limbic system (the tonsils and the hippocampus).
The insula receives information from the sensory pathways and sends information or stimuli to other structures, such as the limbic system, the ventral striatum, and the orbitofrontal cortex. This area appears to be responsible for experiencing disgust, as is recognizing other people’s expressions of disgust.
In people with Huntington’s disease, for example, the insula does not work properly, making it difficult for them to experience this emotion. In addition, stimulation of the insula leads to nausea.
The limbic system, and specifically the amygdala, is related to negative emotional processing, such as fear, disgust, and learning. Recently, a group of members of the University of Granada and the Autonomous University of Baja California discovered the specific area of the almond that causes the rejection of unpleasant tastes.
Until now, scientific studies have claimed that disgust was part of certain areas of the brain, capturing images of those areas that were thought to be involved. Thanks to new technologies, such as functional magnetic resonance imaging, one can clearly see how the brain processes disgust dynamically.
About a year ago, a group of researchers from Spain subjected 30 people to a study. They presented these people with a six-minute video with images of many tasty dishes. They also showed them another video with images of food alongside other unpleasant things, such as cockroaches and people eating worms.
The results showed that the brain was still processing this emotion 40 seconds after seeing the unpleasant images. In addition, the brain images showed that not only does part of the brain activate at the sight of a disgusting scene or object, but almost half of it.
As for processing, scientists say there are three stages:
- A stimulus appears and the brain begins to activate the body’s defenses and protection mechanisms, even without being aware of it.
- The second stage is one of conscious alertness after the brain judges a stimulus as consciously negative.
- Finally, there is the third stage of assimilation, in which a person experiences disgust and stores it in his memory for future use. This phase can last about 26 seconds.
You may be extremely disgusted by certain stimuli that did not bother you at first. Thus, there are several psychopathological disorders that are either related or at least have a disgust component. The processing of disgust works less well here.
There are some examples of anxiety disorders such as bipolar disorder or obsessive compulsivity where there is an excessive concern about the spread of germs and dirt.
The disgust component is crucial in some phobias such as hematophobia or social phobia. With regard to the latter, it seems that some people feel a certain reluctance or aversion to associate with people. Finally, the role of disgust in eating disorders is still under investigation.