Motivation and emotion/Book/2011/Disgust

Overview
Disgust is an emotion and a type of aversion to stimuli that is found to be extremely unpleasant or offensive whether physical or moral. There are evolutionary theories that seek to explain the phenomenon of disgust. These include survival by detecting tastes that could be potentially dangerous, avoiding a potentially disease-ridden rat or rejecting sexual partners based on poor genes. These genes can present as obesity, diseases and physical deformities often caused by genetic mutation. A disgust reaction can often cause the face to scrunch up and distort the mouth. Disgust has been discussed in the context of emotions particularly by renowned psycholgists Paul Ekman and Robert Plutchik. Ekman's focus was on emotions and emotive expression (His involvement in The Wizard Project), whereas Plutchik developed a Wheel of Emotions. Parrott managed to organise his list of emotions in the form of a table.

In the brain, the insular cortex is the part seen to be particularly active during disgust and observing expressions of disgust. Other physiological symptoms of a disgust reaction can include lowered heart rate and blood pressure, nausea and changes in respiratory behaviour. There has been evidence to suggest that women experience disgust more easily than men, especially when it comes to selecting and more specifically, rejecting a mate.

What is disgust?


Disgust is an emotion as well as a description of the physiological responses to a disturbing stimulus, whether that be a taste, a smell, a sight (visual), something touched (haptic) or even a sound (audio) such as dissonant chords. Other signs and symptoms apart from facial expression can include nausea, lowered blood pressure and lowered heart rate. Disgust can also be elicited from a moral stimulus such as the actions of others. This is known as moral disgust.

Moral disgust
Moral disgust refers to the way a person may feel towards another's actions. For example, "I am disgusted by your behaviour." Examples of such behaviour can be cruelty, selfishness, lack of consideration or almost any other negative behaviour. Moral disgust is also distinct from physical disgust in the way it is culturally defined, whereas physical disgust is prevalent across cultures and is therefore biological. It has been theorised that physical disgust and eventually moral disgust have evolved from a need for humans to avoid certain dangers.

Evolutionary theories
Potential hazards for humans can be found everywhere in nature. It is for this reason that humans have evolved disgust.

For example, rotting food, bodily fluids, animals (including parasites and insects) and signs of infection can all be hazardous to a human and also are likely to elicit a disgust reaction. A mutation may occur in a gene that causes a human to dislike the taste of a certain poisonous food. That human then passes on this mutation to his or her offspring who, therefore, also feel disgust with this food, they survive, and they pass on the helpful gene. And so on and so on. If they did not receive this mutation they might not have survived to pass along the gene and therefore the gene would have died out.

This phenomenon would not happen in the same way if the food were not hazardous to a human's health because the gene would not affect survival and therefore its own preservation by being passed down and causing non-recipients of the gene to die. Disgust has taken this hereditary path of passing genes down to offspring to become part of the human condition.

Paul Ekman
Paul Ekman was a psychologist who was named one of the top 100 influential people of 2009 by Time Magazine. He is widely known for his work in the field of emotions, and how facial expressions can express them to others.

His most famous piece of work was one named The Wizards Project. In this project he and Dr Maureen O'Sullivan tested participants' ability to detect lies in other people. From this study of 20,000 participants, they found that about 50 people of this sample (approx. 0.25% of the sample) showed great skill in detecting lies and would be able to correctly recognise a liar to at least 80% accuracy. This is a highly significant rate of accuracy compared with the rest of the sample who could only identify liars to about 50% accuracy, which is the expected accuracy if they had simply guessed. They coined the term 'Truth Wizards' for these seemingly gifted individuals. A television show was inspired by this research finding named Lie to Me.

In 1972 devised a list of six basic emotions. These included:


 * Anger
 * Disgust
 * Fear
 * Happiness
 * Sadness
 * Surprise

18 years later in 1990 he revised the list to include 11 more emotions. These were:
 * Amusement
 * Contempt
 * Contentment
 * Embarrassment
 * Excitement
 * Guilt
 * Pride in achievement
 * Relief
 * Satisfaction
 * Sensory pleasure
 * Shame
 * Shame

Ekman gained criticism in his work due to his theories not being subjected to scientific experimentation. Another limitation to Ekman's list is that he fails to take into account that many emotions are raw and many are derived from these raw emotions. Robert Plutchik attempted to make his own list that takes this problem into account.

Plutchik's wheel of emotions


Robert Plutchik devised a list of his own in 1980. This list was organised into a wheel and was comprised of 8 basic emotions and 8 advanced emotions that are made up of two basic ones. The basic ones include:


 * Joy
 * Trust
 * Fear
 * Surprise
 * Sadness
 * Disgust
 * Anger
 * Anticipation

The second list of 8 advanced emotions are made up of combinations of the previous 8 basic emotions. These advanced emotions are:


 * Optimism (Anticipation + Joy)
 * Love (Joy + Trust)
 * Submission (Trust + Fear)
 * Awe (Fear + Surprise)
 * Disappointment (Surprise + Sadness)
 * Remorse (Sadness + Disgust)
 * Contempt (Disgust + Anger)
 * Aggression (Anger + Anticipation)

Trying to organise emotions into a list is very difficult because some emotions are raw and some are derivatives of other emotions. This method of organisation has tried to address this problem whereas Paul Ekman's list does not.

Parrot's Emotions by Groups
W. Gerrod Parrott developed his own inventory of emotions presented in the form of a list sorted into a tree-like structure. Below is a table taken from Wikipedia:

As it can be seen in the table, Parrott names what seems like every single emotion thinkable which can be a strength and a weakness. It's a strength because it leaves no stone unturned and seeks to explain every aspect of emotion in as much detail as possible. However, it's also a weakness because there is a tendency for some of these many emotions to double up. For example some people might argue that amazement and astonishment are the same thing.

Cognitive theory of emotion
There have been numerous theories put forward to explain emotion with a cognitive approach. Many of these also share a physiological perspective. One such example is the Two-factor theory of emotion. This theory was tested in a study performed in 1962. Their paper concluded with 3 points:
 * 1) Given a state of physiological arousal for which an individual has no immediate explanation, he will label this state and describe his feelings in terms of the cognitions available to him. To the extent that cognitive factors are potent determiners of emotional states, it should be anticipated that precisely the same state of physiological arousal could be labeled [sic] "joy" or "fury" or "jealousy" or any of great diversity of emotional labels depending on the cognitive aspects of the situation. (p. 398)  This point explains that in their study they found that cognitive patterns determine how we label our physiological states with words such as 'joy, 'fury' or even 'disgust'.
 * 2) Given a state of physiological arousal for which an individual has a completely appropriate explanation, no evaluative needs will arise and the individual is unlikely to label his feelings in terms of the alternative cognitions available. (p. 398)
 * 3) Given the same cognitive circumstances, the individual will react emotionally or describe his feelings as emotions only to the extent that he experiences a state of physiological arousal. An experiment is described which, together with the results of other studies, supports these propositions. (p. 398) This third point illustrates how emotions are based on physiological factors, specifically the level to which the individual is physiologically aroused.

Gender differences in disgust responses


Women have been found to report stronger feelings of disgust than men according to a study in 2008. The responses in the study measured heart rate, electro-dermal activity, salivary cortisol and secretory immunoglobulin A. The study concluded that:


 * Replicating previous studies, women reported stronger feelings of disgust than men across all disgust inductions. Additionally, in Study 1, women showed a higher increase in skin conductance level than men. In conclusion, gender moderates subjective responses to disgust, whereas physiological disgust responses are only marginally moderated by gender.

Physiology of disgust


As mentioned in the introduction, the insular cortex is the most active part of the brain when an individual is experiencing disgust or is observing others expressing disgust. The Wikipedia page for Cognitive Neuroscience and Disgust lists physical, autonomic responses that can arise from feeling disgusted. They are listed as "reduced blood pressure, lowered heart rate and decreased skin conductance along with changes in respiratory behaviour."

A study in 2007 investigated activity in the brains of participants when presented with disgust- and fear-inducing stimuli. The study was comprised of 66 participants who were each presented with 50 images that elicited different emotional responses (10 neutral, 20 fear-inducing and 20 disgust-inducing). Each picture was presented for 4 seconds and each participant rated the picture on how fear-inducing or disgusting it was. Each participants brain activity was monitored using fMRI.

The study found that:


 * Both emotional stimulus categories resulted in activations in the extended occipital cortex, in the prefrontal cortex, and in the amygdala. However, insula [sic] activations were only significantly correlated with subjective ratings of disgust, pointing to a specific role of this brain structure in the processing of disgust. (p. 663)

This study aimed to settle discrepancies in earlier studies that presented unclear evidence in the distinction of structures engaged during fear and disgust. The study appears to have been successful in its goal.

Summary
Disgust has been given to the human race by the blind watchmaker known as evolution. It has helped us survive against poisonous substances that without it, would have killed us. Moral disgust has helped guide our morals and ethics to lead us to better interpersonal relationships. It is important to think of disgust as not just a word that describes a reaction, but as an emotion in itself as outlined by Paul Ekman in his list, or Robert Plutchik in his wheel or W. Gerrod Parrott's table. It is not just a series of cognitions that trigger an emotional response, but an intricate network of cognitive, emotive and physiological systems working together to produce what is known as disgust.