the science of disgust

A look at the things that make us go, “ick!”

What would you do if you were standing in a room filled with artificial fart spray? Yep, you’d probably want to leave – but you’d also become more likely to judge others harshly, thus becoming an arsehole yourself (appropriately enough). We know this thanks to psychologist David Pizarro, one of the many scientists around the world dedicated to understanding the emotion of disgust. (Fun fact: said scientists sometimes like to refer to themselves as ‘disgustologists’.) Of course, the folks who agreed to participate in Pizarro’s experiment weren’t told they’d be trapped in a fart chamber for the duration. Sure enough, though, they were – and, once inside, were asked to rate how they felt about various groups in society, such as the elderly. While the scent of human stink bombs tickled their nostrils, the participants were more likely to disapprove of their fellow humans than when they were in a neutral-smelling environment. But why?

Scientists believe disgust originally evolved to protect us from getting sick and dying – hence why we’re universally grossed out by anything or anyone that looks potentially infectious: rotten food; critters widely considered to be vermin (cockroaches, rats, lice and such); dead bodies; body fluids; signs of physical damage (open weeping sores, for example). When you feel your skin crawl at the sight or smell of these things, you’re experiencing ‘pathogen disgust’ – considered a component of your behavioural immune system. It’s biologically advantageous, both individually and collectively, not to touch cockroaches or lick someone else’s rash, so, in this way, disgust is protecting us. Yay, disgust. Where it gets weird is the concept of moral disgust – as per Pizarro’s experiment. Why would other people disgust you, just because they’re different? The thinking goes that once upon a time (i.e. in pre-modern society) disgust was super-essential because it kept us alive – it stopped us from eating poo, maggots or both. However, now we’re better able to detect which foods will kill us, disgust has evolved to take on a new role: to protect us from people we believe will ‘poison’ our morals. So, when someone does or says something that contradicts our beliefs, we are repulsed.

But not everyone is repulsed to the same extent. Generally speaking, if you’re easily disgusted, you’re probably more judgmental towards others. Old mate Pizarro discovered that your threshold for disgust directly corresponds to your political views. Are you an extreme conservative? Then it’s easy to make you say ‘ew’. Fierce liberal? Way less so. But put you in a room full of farts, and you’ll all start breaking down eventually – such is the power of human gas. You’ll also become worse at bargaining, as psychologists at Carnegie Mellon University recently discovered. These particular disgustologists showed their experiment participants a whole bunch of revolting videos, then asked them to sell stuff. The folks who’d witnessed the gross-out reel sold their items for around half the price of those who’d watched neutral clips, thus demonstrating the ‘disgust disposal effect’. Not only does it make you want to ditch disgusting things, it also drives you to remove yourself from any situation you find disgusting. In the Carnegie Mellon experiment, the disgusted people accepted mediocre trade deals in order to get out of there quicker – but you’ll also find people will distance themselves from folks they find distasteful, physically and/or psychologically. Not children, though. One need only spend a brief amount of time in the company of tots to be introduced to their boogers and other things that should (according to the pathogen disgust response) cause them to cringe. Disgust is one of the last emotions kids get their head around, you see. It kicks in at around two years old

– i.e. when they become independent from their parents. But even once they hit nine years, they’ll only correctly interpret a disgusted expression around 30 per cent of the time. That mightn’t seem like

a huge deal, but scientists say the disgusted expression – the curled upper lip, accompanied by wrinkled nose and brows – acts as a warning sign to other members of the species to avoid a gross thing. Which probably explains why it’s a human universal

– even blind people make that face.

On the whole, women report feeling disgusted more often than men, and pregnant women are the most easily disgusted people of all. You can blame their increased levels of progesterone for that; the hormone is associated with superhuman smelling powers. Scientists reckon this helps to protect a mum-to-be from threats to her foetus. So, if you’re not sure whether your yoghurt is still OK to gobble down, stick it under a pregnant woman’s nose – she’s the best person to say whether or not it’s going to make you vom.

If you, too, suspect you have pregnant lady levels of detecting mould (or just generally feel ill at the sight of crusted toenails and the like), you have what scientists call ‘high disgust sensitivity’, which means you’re also more likely to be freaked out by risk. While your ‘low disgust sensitivity’ comrades will happily go sky-diving or whitewater rafting, for example, you’ll (probably) assess the potential threat to your life and sit these activities out, preferring to eat a germ-free square of chocolate fudge and play UNO on a grassy knoll. The same is true of financial risk (easily repulsed pals will opt out; not-so-repulsed folks will opt in), and social risk. Consider that person who voices an unpopular opinion or speaks to their higher-ups at work about a controversial topic. Well, that person is less likely to feel their stomach turn at the sight of pus. Now you know.

But do you ever find yourself curious to look at a pustule, even though you find it intensely sickening? That doesn’t make you an oddball. On the contrary, it makes you normal. It’s human to feel strangely attracted to whatever disgusts you, which is why we can find ourselves watching gory movies or entranced by gross photos online. Not only is this a safe way to experience disgust, it’s also a form of psychological arousal. A bit like riding a rollercoaster. This arousal triggers the reward centre of the noggin – and some neuroscientists are even inclined to believe the arousal we feel from disgust is more powerful than the arousal we feel from something desirable.

Yep, it’s all a bit mind-bending. But then, this whole business of disgust is. Take cheese. The stinky kind. Your blue cheeses, riddled with fuzzy bacteria that, according to the rules of pathogen disgust, should makes us all reach for the nearest bucket. Some of us adore said cheese, while others abhor it. To find out what makes certain folks lust after mould-ridden dairy products, researchers at the University of Lyon in France used MRI imaging to look at the brains of cheese lovers and cheese haters, after sniffing and viewing different forms of fromage. Scan after scan yielded no neurological data – the researchers were stumped.

Psychologist Paul Rozin (also known as Dr. Disgust on account of the fact he’s spent a lifetime researching disgust

– not because he bathes in his own urine) suggests the reason behind the varying reactions to gorgonzola are to do with negative experiences. That, or because we experience different sensory chemistry. The butyric and isovaleric acid in parmesan can smell like vomit, for example, yet so many of us grate it over our bolognese. So, feel free to point that out the next time you go to an Italian restaurant with your mates. If they tell you you’ve spoiled their time by doing so, inform them that easily disgusted people tend to be ultra right-wing.

You won’t necessarily make any friends at the table, but it might mean you get extra cheese.