Article curated by Ginny Smith
Disgust is an emotion and bodily sensation thought to have evolved to protect us from infection or poison by making us avoid potentially dangerous substances such as bodily fluids or rotten meat. However it has now become more complex than simply a way of keeping us safe from disease, in ways we don't fully understand.
We have all felt that crawling feeling of disgust at a maggot or a pile of vomit. This feeling of repulsion helps protect us from disease by making us avoid potential sources of contamination or infection. However, we also feel disgust towards certain acts of behaviour which we deem unacceptable, suggesting disgust has a moral component as well.
Delve deeper into emotions.
Disgust has the interesting property of being contagious- anything that has been in contact with a disgusting object becomes disgusting itself. This make a lot of sense for its original purpose- food that has been dropped into dog poo is no longer safe to eat. However this contagion, and the idea of disgust itself, has expanded into areas no longer linked with keeping us safe from pathogens . People who carry out acts thought to be immoral are often labelled as ‘scum’ or ‘animals’- words associated with disgust objects. This can lead to the dehumanisation of certain social groups, and those associated with them 2. People will often avoid associating with them, or even being in close proximity to them for fear of some sort of ‘moral contagion’- a completely irrational behaviour, but one which is extremely hard to change. People are even hesitant to wear Hitler’s jumper even though there is no physical threat from wearing a jumper that was once worn by a murderer3.
Despite the common claim that we are disgusted by immoral behaviour, it is unclear whether we really do experience disgust, or whether it is more of a metaphor. Research by Professor Roger Giner-Sorolla suggests that when the immoral behaviours relate to the body (e.g.incest), disgust is felt, but for other acts the main emotion felt is anger , even when people claim to find the behaviour disgusting (e.g. using a crucifix as a doorstop)4. It isn’t clear whether true disgust can ever be felt for things that aren’t related to the body, although many researchers claim it can. It may be that culture has co-opted the emotion of disgust, but that it has become something subtly different when applied to non-bodily aspects. Contempt, for example, is a very closely related emotion- even the facial expressions for disgust and contempt are remarkably similar. This emotion may have developed as a way to signal dislike for something or somebody, in the same way disgust does, but without the full blown bodily reactions which are no longer necessary to protect you from infection.
Does disgust sensitivity affect political beliefs?
Moral rules, such as those imposed by religions around the world, often include strong disgust-linked components- limits on sexual practices, women being ‘unclean’ during their periods and controls on what can and cannot be eaten are all common, and all linked to disgust. When humans first began leaving our hunter gatherer routes and coming together in bigger and bigger numbers, the importance and number of these rules increased. In modern times, disgust-based laws are reducing, as harm is seen as more important. The end of apartheid and rules against interracial or same-sex marriages are recent changes- these are behaviours which once would have elicited disgust, but now are seen as acceptable by the majority of the western world. However there are still people who are against these sorts of changes, which opens up the question of why they feel that way- does disgust have a role to play in people’s political ideologies? Many studies have found that yes, people who are more liberal tend to be less easily disgusted than those who are more conservative (these studies have mainly been carried out in the US, so use their political scale) 5. However these are correlational studies, so we can’t simply claim that being easily disgusted makes you more conservative. There could be a third factor that affects both disgust sensitivity and political views, or it could be the political leaning that causes you to become more sensitive to disgust. In fact, it seems the best predictor of both disgust sensitivity and politics is a person’s ‘openness to experience’- whether they seek out and enjoy new experiences, or whether they prefer to stay in their comfort zone6. Work by Matthew Feinberg has suggested that it might be related to how much someone ‘trusts their gut’7. Conservative standpoints don’t take a lot of cognitive resources- they rely on intuition. People who are less likely to go with their gut, and take bodily sensations on face value may experience less disgust and also be more liberal, because they react less to the emotions they experience.
Researchers have tried to unpick this link further by inducing disgust in a lab setting, and seeing whether this changes people’s moral judgements- but here there is major disagreement. Jonathan Haidt and his colleagues claim to have found that people become more judgemental when they are disgusted8,9, but others claim that his experiments may have induced anger in the subjects, who were asked to carry out a task in a filthy classroom full of half-eaten pizza and rubbish bags. A recent meta-analysis by Geoffrey Godwin & colleagues found a small but significant effect, but once they accounted for publication bias this effect vanished. In response, Haidt claimed that within the meta-analysis were finding that supported his view- if you look solely at inductions using smell or taste for example. It seems that it may be some time before this issue is fully resolved.
If our feelings of disgust and our moral judgements are linked, this raises the question of whether our laws should fit in with our disgust reactions, or be used to control them. One area in which this is rapidly changing relates to sexual behaviours. Evolutionarily, and until fairly recently, sex and reproduction were inextricably linked. The majority of taboos and laws around sex have historically been to help ensure the viability of the offspring. It made sense, for example, to mate with someone unrelated, but from a similar background, who was fit and healthy, of reproductive age, and of the opposite sex to you. This led to taboos around sex with the very old or very young, those who were deformed or otherwise unattractive (as this signalled bad health or genetics, which could be caught or passed on to the offspring), and those from different races. Now, developments in contraception and reproductive technology have meant that sex and reproduction are no longer necessarily linked. Does this mean that our laws and taboos should change as well? In many cases, such as homosexuality and interracial relationships they already have, but others, such as incest, remain off limits. The idea fills us with disgust, but if the relationship is consensual and won’t lead to offspring being produced, where is the harm? And if there is no harm, is it really something that should be legislated against? The variety of different relationships that are illegal in different countries around the world shows that this is far from a simple matter.
Another area of interest is whether our disgust reactions having an impact on our behaviour, and the decisions we make every day. Some scientific advances, for example, come up against much stronger reactions than others. Consider GM food; despite there being no evidence that undermines its safety for human consumption, huge numbers of people avoid it, and campaign for it to be banned. And even governments are being swayed by this- Scotland recently banned the growth of GM crops, to widespread outrage in the scientific community. Our disgust reactions are strongest when it comes to food, so could it be that we are letting ourselves be led by our gut? The idea of putting something ‘unnatural’ or ‘frankenstein’ into our bodies may trigger such a strong feeling of repulsion it overrides any amount of data showing the safety of the product. How we can change this reaction is a huge challenge, and one we will have to face if we want to ensure food security for our growing population.
Despite being a basic emotion, experienced all over the world, we don’t all feel disgust in the same way. On average, women tend to report feeling more disgust than men when looking at something unpleasant 9. However, this only holds true in western countries like the UK and the US. In other places, such as Ghana and Turkey, women and men have much more similar levels of disgust10. This raises the question- why are there such differences in the west? When the data is analysed, it becomes clear that western men are the ‘odd ones out’, experiencing unusually low levels of disgust. So why could this be? One theory is evolutionary- women have to protect their pregnancies and children, who are more at risk from pathogens, so are more wary of potentially infectious objects. This fits with the finding that disgust sensitivity increases in women when they are pregnant. It wouldn’t, however, explain why the cultural difference is found. Another theory is that the difference is being driven by western women- when asked, a group of US university students marked a partner lower than them in disgust as a highly desirable trait-more desirable than one low in anger 11. When you measure people’s physiological response to something disgusting- looking at their heart rate, or brain responses, the difference disappears. This could mean that western men feel the same amount of disgust, but are pressured by society and women’s desires to play it down, and not admit to feeling it. However it could also be that our physiological measures simply aren’t sensitive enough to detect the differences.
Disgust is a fascinating emotion, that may impact more aspects of our lives that we ever thought. Future research will look to unpick just how our feelings of disgust vary from person to person, how these influence our decision making, and whether we should continue to allow them to.
This article was written by the Things We Don’t Know editorial team, with contributions from Ginny Smith, and Johanna Blee.
why don’t all references have links?
 Valerie Curtis, Mícheál de Barra, Robert Aunger, (2011) Disgust as an adaptive system for disease avoidance behaviour Philosophical Transactions of the Royal Society B: Biological Sciences 1563/366 DOI: 10.1098/rstb.2010.0117
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 Rozin, P., Millman, L., and Nemeroff, C., (1986) Operation of the laws of sympathetic magic in disgust and other domains Journal of personality and social psychology 50.4:703-712
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 Feinberg, M., et al, (2014) Gut check: Reappraisal of disgust helps explain liberal–conservative differences on issues of purity Emotion 14.3:513
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