In North Carolina, there's a company that manufactures bottles of an artificial fart spray called Liquid Ass™. The makers (who call themselves Assman #1 and Assman #2) are clearly proud of their product, writing lyrically on their website of its "genuine, foul butt-crack smell with hints of dead animal and fresh poo".
The site also features user testimonials, mostly along the lines of "I sprayed this stuff all over a friend's car, then laughed myself silly as he tried to work out where the stench came from".
What the website fails to mention, however, is the vital role these little bottles of nastiness are playing in the cutting-edge experiments conducted, in perfect seriousness, by Auckland University psychology researchers.
Over the past few years, a team has been luring experimental subjects into a small room on the 12th floor of a building in Auckland City Hospital, putting them into a state of mild disgust with a covertly deployed dose of Liquid Ass (which, despite the stench, is non-toxic), then running a battery of psychological tests.
Other adventures facing the subjects included being handed a bag that looked like it may once have contained excrement.
It's tempting to think that this proves little more than the popular hypothesis that psychologists are sadistic weirdos, but in fact these experiments are yielding powerful insights into the nature of human emotions.
More practically, they are providing clues for how to deal with some of the most intractable problems facing modern healthcare.
The man behind these experiments is Associate Professor Dr Nathan Consedine, director of the health psychology programme in the Department of Psychological Medicine.
He's 42, has a skinny moustache vaguely reminiscent of Salvador Dali's, and has been studying emotions and their role in healthcare throughout a career that began in Christchurch and has included long stints at Columbia University and Long Island University in New York.
It was only in 2009, though, after returning to New Zealand, that Consedine started paying close attention to the significance of one emotion in particular: disgust. It is, says Consedine, the "elephant in the room" when it comes to healthcare.
Consider the well-acknowledged problem of sick people avoiding the health system: ignoring symptoms, skipping checkups, denying there's a problem, failing to follow the course of treatment. Economic and other factors matter, of course, but so do the emotions experienced by patients. Numerous researchers have looked into the importance of fear in healthcare, both as a motivator and demotivator, and a few have looked at embarrassment. Disgust, though, barely gets a look-in.
A few years ago, Consedine counted some 40,000 academic papers looking at the role of fear. There were just six on the role of disgust. But the more Consedine thought about it, the more he realised that almost everything about health is gross.
"Symptoms are icky, tests are icky, diagnosis is icky, treatments are icky, side-effects are icky. It's all icky."
Yet, somehow, the self-evident fact that healthcare grosses people out, and that the disgust they feel causes them to avoiding proper treatment, hasn't been formally investigated. He's starting to put that right. First, though, what exactly is disgust?
Depending on who you ask, humans experience somewhere between 10 and 20 emotions. Disgust, says Consedine is one of the five or six "basic" ones - defined as those that appear early in a person's development, are universal across cultures, have a distinct and recognisable facial expression and have a clear impact on the person's behaviour. (The other "basic" emotions are sadness, fear, anger, happiness and, arguably, surprise.)
Each emotion has evolved over millions of years, and each has a useful function. Sadness "facilitates adaptation to loss", fear helps you avoid physical threat; happiness reinforces success and facilitates social interactions; anger gives you the motivation to "remove goal blockages" (or as Consedine translates: "You hit people when they get in your way").
Disgust is the only basic emotion whose function is all about health - it forestalls or prevents an individual's exposure to pathogens or contaminants, and it's expressed in two main ways.
There's the immediate form of disgust, where you screw up your face, your nostrils constrict, your mouth floods with saliva and you may even give a little heave. It's your body preparing to spit and/or vomit, to eject something dangerous as fast as possible.
"The prototype is if I bite into an apple, and I feel a worm wriggling on the end of my tongue, and I go yeccchhh!"
The other manifestation of disgust is anticipatory: it influences our decision-making so we keep physically distant from disgusting things. So imagine, says Consedine, that you're at an outdoor music event and you realise you need to use a Portaloo.
"You get about 30 metres away and get your first whiff and suddenly you think - ahhh, maybe I don't need to use the toilet that badly". That's an anticipatory disgust response leading to avoidant behaviour.
So what are the threats disgust protects us from? There are three main types, says Consedine: exposure to bodily products (spit, faeces, semen, earwax, blood etc, though not, curiously, tears); rotten food and reminders of rotten food, including rodents and cockroaches and flies; and also what Consedine calls "violations of the body envelope".
This means we get freaked out by things being put inside people, whether we're hearing an urban myth about a famous actor and gerbils, dressing a wound or watching an injection.
(There is an obvious problem here concerning intercourse and other sexual activities, but evolution has that sussed too - sensitivity to disgust falls dramatically with sexual arousal.)
Disgust sensitivity also varies from person to person, and like all emotions, it is "pretty loosely calibrated", says Consedine, which is why you can be disgusted by something that's not actually pathogenic - a food with a slimy texture, say, or a photo or a story about something disgusting.
(I can vouch for the fact that talking and writing about the subject of disgust can leave you rather queasy.)
In fact, there is a fourth category, slightly less connected to health, which may be a kind of recycling of the mechanisms of disgust in a social setting: the "moral" disgust which means some people are physically revolted by the behaviour of others.
"The system gets used socially to manage a moral behaviour - gay marriage, paedophilia, incest, adultery - where realistically there is little immediate health threat to me if someone wants to engage in those behaviours."
Several studies have demonstrated links between moral disgust and political leanings. In particular, political conservatives tend to be more disgust-prone, and if you disgust someone under experimental conditions (such as exposing them to disgusting smells) they will make more conservative choices in political questionnaires.
Consedine's research is more concerned with health than politics though. That's where the fart spray came in.
He wanted to test the connection between disgust and avoidant behaviour by getting people into the lab, manipulating their disgust levels, then testing their behaviour. So in 2011 and 2012 Consedine and his students Lisa Reynolds and Sarah McCambridge conducted two trials involving around 170 people (who didn't know the true intent of the studies).
As each subject turned up the researcher would duck into the interview room, and for 50 per cent of the subjects, they'd spray the Liquid Ass into a bin hidden under the table, making the room reek. (Showing subjects disgusting pictures or movies would work too, but would give the game away.)
Consedine takes this stuff seriously, but he realises it's kind of funny to do an experiment where you make the room smell of poo. He says the subject would step in, look around for the source of the smell, maybe inspect the bottom of their shoe, but the researcher would have to act as if nothing was wrong. "It was awkward."
Once suitably disgusted (or not, as the case may be), subjects were asked to consider healthcare scenarios, such as "three days after the last time you had sex you wake up and you've got crusty bits all over yourself - will you make an appointment that day? Or later? Or never?".
One trial was focused on sexually transmitted diseases, the other on colorectal cancer - both areas where "disgust elicitors" are never far away, whether it's handling one's own faeces for a stool test, or fronting up to a sexual health clinic where a stranger may shove a finger or object into you. The results were striking: subjects who had been pre-disgusted by the nasty smell were markedly more likely to make avoidant choices during the scenarios. What's more, the researchers made sneaky observations of their actual behaviours too.
They would be handed a plastic bag of the type used by some bowel-cancer patients to collect faeces from a stoma on their belly. The bag had been deliberately made to look like it was slightly soiled. Subjects in a smelly room consistently held the bag for a shorter time.
A smelly room also made subjects more likely to turn down an offer of a glass of water and to choose a wrapped sweet over an unwrapped sweet. They tended to choose a chair further from the interviewer.
"What this means," says Consedine, "is that any condition, examination or treatment that increases disgust is going to make people socially avoidant, because other people are the main source of contaminants."
The studies were published this year in the American Psychological Association journals Health Psychology and Emotion.
Sure, says Consedine, the behaviours you observe in a laboratory are simplified compared to real life. But the experiments still provide powerful evidence of the importance of disgust in encouraging avoidant behaviour, "and I have no doubt that it's happening in real life".
In real life, it's too soon to say how a health system might make practical use of the findings, but Consedine believes there are hints in approaches already successfully used to manage fear among patients, where a GP will open a conversation by suggesting it's OK to be scared.
For some reason this is seldom done around disgust, says Consedine. "But if you have a GP saying to people ‘this could be a bit icky but I think you've got to do it anyway', I think that will make a lot of difference. Otherwise you're pretending that the disgust either isn't there or shouldn't be there.
"But why not? We're biological organisms that are designed to get disgusted by disgusting stuff and there's a reason for that. And it can be overridden."
Consedine is in close contact with about a dozen disgust researchers around the world, but says he's almost the only one focusing on disgust with respect to health. He says it's exciting to be in virgin research territory, "but risky too, as there is a lack of precedent to guide you, and it can be harder to sell in the market of research.
"But it's starting to come now."
Are you interested in taking part?
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