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People Sometimes Like Stinky Things—Here’s Why

Updated September 30, 2015

A corpse flower smells like a heady mix of rotten fish, sewage, and dead bodies. It’s a stench meant to draw flies, but just as surely, it draws tourists. Braving a blustery Chicago night, thousands of people lined up Tuesday for a whiff of a corpse flower named Alice at the Chicago Botanic Garden.

This woman shows a classic "disgusted" face in a video about the 2013 blooming of a corpse flower (see video, top).
This woman shows a classic “disgusted” face in a video about the 2013 blooming of a corpse flower (see video, top).

In fact, the demand to see and smell a corpse flower is so great that botanical gardens now vie to own one. Gardeners lavish them with care, hoping to force more stinky blooms from a plant whose scent is so rare (up to a decade between flowerings) and so fleeting (eight to 12 hours) that visitors are often disappointed to miss peak stench.

But why do people want to smell the thing? The reaction is usually the same: the anticipation, the tentative sniff, then the classic scrunched-up face of disgust. And yet everyone seems happy to be there.

It turns out there’s a name for this: benign masochism.

Psychologist Paul Rozin described the effect in 2013 in a paper titled “Glad to be sad, and other examples of benign masochism.” His team found 29 examples of activities that some people enjoyed even though, by all logic, they shouldn’t. Many were common pleasures: the fear of a scary movie, the burn of chili pepper, the pain of a firm massage. And some were disgusting, like popping pimples or looking at a gross medical exhibit.

The key is for the experience to be a “safe threat.”

“A roller coaster is the best example,” Rozin told me. “You are in fact fine and you know it, but your body doesn’t, and that’s the pleasure.” Smelling a corpse flower is exactly the same kind of thrill, he says.

It’s a bit like kids playing war games, says disgust researcher Valerie Curtis of the London School of Hygiene and Tropical Medicine. “The ‘play’ motive leads humans (and most mammals, especially young ones) to try out experiences in relative safety, so as to be better equipped to deal with them when they meet them for real,” she says.

People around the world make the same face when disgusted, with a downturned mouth and sometimes a protruding tongue.
People around the world make the same face when disgusted, with a downturned mouth and sometimes a protruding tongue.

So by smelling a corpse flower, she says, we’re taking our emotions for a test ride. “We are motivated to find out what a corpse smells like and see how we’d react if we met one.”

Our sense of disgust, after all, serves a purpose. According Curtis’ theory of disgust, outlined in her insightful book “Don’t Look, Don’t Touch, Don’t Eat,” the things most universally found disgusting are those that can make us sick. You know, things like a rotting corpse.

Yet our sense of disgust can be particular. People, it seems, are basically fine with the smell of their own farts (but not someone else’s). Disgust tends to protect us from the threat of others, while we feel fine about our own grossness.

Then there are variations in how we perceive odors. Some smells are good only in small doses, as perfumers know. Musk, for instance, is the base note of many perfumes but is considered foul in high concentrations. Likewise for indole, a molecule that adds lovely floral notes to perfumes but is described as “somewhat fecal and repulsive to people at higher concentrations.”

University of California Botanical Garden
University of California Botanical Garden

No one has yet, to my knowledge, tried out a low dose of corpse flower in a perfume (though you can try on an indole brew in “Charogne,” which translates to “Carrion,” by Etat Libre d’Orange). But someone could. There’s an entire field of perfumery—called headspace technology, it was pioneered by fragrance chemist Roman Kaiser in the 1970s—that’s dedicated to capturing a flower’s fragrance in a glass vial and then re-creating the molecular mix chemically. I would love to see someone give eau de corpse flower a whirl, if only they can find a headspace vial large enough.

The stench of a corpse flower, after all, is a mix of compounds, including indole and sweet-smelling benzyl alcohol in addition to nasties like trimethylamine, found in rotting fish. So I’d be very curious to know if a small amount of corpse flower would be a smell we would hate, or maybe love to hate.

I’ll leave you with my favorite example of a “love to hate” smell, from my childhood in the 1980s. At a time when I loved Strawberry Shortcake dolls and scratch-and-sniff stickers, the boys in my class were playing with He-Man dolls. Excuse me, action figures. And among the coolest, and grossest, of them was Stinkor. He was black and white like a skunk, and his sole superpower was to reek so badly that his enemies would flee, gagging.

To give Stinkor his signature stink, Mattel added patchouli oil to the plastic he was molded from. (This confirms the feelings of patchouli-haters everywhere.) It meant that you couldn’t wash Stinkor’s smell away, and it wouldn’t fade like my Strawberry Shortcakes did. The smell was one with Stinkor. And of course, children loved him.

Writer Liz Upton describes the Stinkor figure that she and her brother adored (their mother did not). The kids would pull Stinkor out and scratch at his chest, smelling him again and again. “Something odd was going on here,” Upton writes. “Stinkor smelled dreadful, but his musky tang was strangely addictive.”

If you’re the kind of benign masochist who wants to smell Stinkor for yourself, you can pay $125 or more for a re-released collector’s edition Stinkor—or you can just find an old one on eBay. The amazing thing: 30 years later, the original Stinkor dolls still stink. And people still buy them.

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We Can Distinguish Between At Least A Trillion Smells

Guesses have a strange way of disguising themselves as facts, and taking root in popular knowledge. Consider the claim that the human nose can distinguish between 10,000 different smells. The statement crops up in all manner of websites, along with textbooks and scientific publications.

The figure came from a paper published in 1927, which suggested that people could tell the difference between odours according to four different qualities—fragrant, acidic, caprylic, and burnt—along a nine-point scale. That gives us 6,561 distinguishable smells, which was later rounded up to 10,000!

And that’s it.

There wasn’t any evidence for any of these assumptions, but that didn’t stop an uneducated guess from becoming enshrined as fact.

When Andreas Keller at Rockefeller University learned about this, he was dissatisfied. He wanted to come up with a better estimate—one rooted in actual experiments.

Similar estimates already exist for vision. We know that our eyes are sensitive to wavelengths of light between 390 and 700 nanometres—that is, from red to violet. By doing comparisons within that range, scientists have shown that we can tell the difference between 2.3 million and 7.5 million colours.

The same applies to sound. We can hear frequencies between 20 and 20,000 Hertz—from four octaves below middle C to many octaves above it. Within that range, we can discriminate between around 340,000 tones.

But colours and tones are easy to probe. Both vary along a single dimension: wavelengths of light and frequencies of sound, respectively. Smells don’t have an equivalent. They are complicated cocktails of molecules; a rose, for example, owes its scent to some 275 ingredients. There’s no single metric that we can measure these against; instead, we’re forced to describe them with subjective adjectives. And unlike light and sound, which we can perceive within certain boundaries, there is potentially no limit to the combinations of molecules that could make up an odour.

To estimate the bounds of our sense of smell, Keller had to get creative.

He gave volunteers three jars, two of which contained the same smell. Their job was to find the odd one out. The team made the smells from the same pool of 128 ingredients, which were mixed together in groups of 10, 20 or 30. They then paired these mixtures up so that some pairs had no ingredients in common, some were almost identical, and most were somewhere in between. Each volunteer sat through 260 of these discrimination tests.

After crunching the numbers, the team found that when the pairs of mixtures overlapped by less than 51 percent, most of the volunteers could tell the difference between them. And if they overlapped by less than 57 percent, most of them were distinguishable. This means that the average person can tell the difference between 1.7 trillion (that’s 1,700,000,000,000)different combinations of 30 ingredients.

“It’s one of those moments you live for as a scientist: reframing a problem and finding the solution out in left field,” says Avery Gilbert, a smell scientist who first tracked down the origins of the spurious 10,000 number.

The 1.7 trillion figure is an average. At least one person in the study had an exquisitely sensitive nose that could potentially discriminate between more than 10 million trillion trillion combinations of 30 ingredients. Another volunteer could only make out around 70 million of them.

There’s good reason for this variability. The genes that create smell receptors—the proteins that recognise the molecules we inhale—are the largest family of genes in our genome. They’re also more variable than other genes. “As a consequence, everybody smells the olfactory environment with a different set of receptors and therefore perceives it differently,” says Keller.

The 1.7 trillion figure is also a gross underestimate. “There are probably billions of odorous molecules and we only worked with 128 of them,” says Keller. “Furthermore, we only mixed 30 components. There are many more mixtures with 40 or 50 components.”

Still, a trillion smells is still many more than the number of colours or tones we can perceive. There’s good reason for that too. “Smell evolved to help us detect small differences between different smells: the smell of my baby compared to the smell of my neighbour’s baby, or the smell of fresh milk compared to the smell of spoiled milk,” says Keller. “There really is no need to discriminate trillions of smells, but there is a need to discriminate very similar smells. As a consequence, we can discriminate very many different smells.”

“The numbers are staggering yet not that surprising,” says Gilbert. “Smell is, above all, a combinatoric sense. There is a large but finite number of odorous molecules in the world and they occur in an endless array of mixtures and concentrations. Yet here we are, sniffing at them and making these incredibly fine discriminations on a daily basis. We handle the complexity pretty well.”

“If we couldn’t discriminate a trillion different mixtures where would we be?” he adds. “We’d know when to take the garbage out, but we wouldn’t be able to tell one vintage of Bordeaux from another. In fact, if we couldn’t discriminate millions of combinations we wouldn’t have bothered to create Bordeaux in the first place.”

Reference: Bushdid, Magnasco, Vosshall & Keller. 2014. Humans Can Discriminate More than 1 Trillion Olfactory Stimuli. Science http://dx.doi.org/10.1126/science.1249168

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The “white noise” of smells

Meet Laurax, a not-very-bold, not-that-exciting new fragrance. According to a panel of sniffers, it’s neither appealing nor revolting. It’s “intermediately pleasant”. People almost trip over themselves to describe it in non-descript terms—“fragrant”, “chemical” and “perfumery”.

Laurax isn’t going to set the perfume world ablaze in the near future, but its scientific implications are fascinating. This bizarre scent is actually a set of completely different fragrances that all smell roughly the same. It’s the odour version of “white”.

The colour that we call white is a blend of many different wavelengths of light. Add red and blue light together, and you get magenta. Add other colours and eventually, you converge on white. The same applies to sounds: if you combine tones of different frequencies, you eventually arrive at a perceptual hum called “white noise”. There’s no fixed formula for making white light or white noise. You don’t need to mix a specific set of colours or frequencies. As long as the individual ingredients are different enough, and roughly equal in intensity, whiteness emerges.


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“Ready steady slow”: time slows down when we prepare to move

A baseball speeds from the hands of a pitcher, a slave to Newton’s laws. But in the brain of the batter who is watching it, something odd happens. Time seems to dawdle. The ball moves in slow motion, and becomes clearer. Players of baseball, tennis and other ball sports have described this dilation of time. But why does it happen? Does the brain merely remember time passing more slowly after the fact? Or do experienced players develop Matrix-style abilities, where time genuinely seems to move more slowly?

According to five experiments from Nobuhiro Hagura at University College London, it’s the latter. When we prepare to make a movement – say, the swing of a bat – our ability to process visual information speeds up. The result: the world seems to move slower.


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Monkeys grab and feel virtual objects with thoughts alone (and what this means for the World Cup)

It's a ninja monkey that fires energy blasts... what could possibly go wrong?

This is where we are now: at Duke University, a monkey controls a virtual arm using only its thoughts. Miguel Nicolelis had fitted the animal with a headset of electrodes that translates its brain activity into movements. It can grab virtual objects without using its arms. It can also feel the objects without its hands, because the headset stimulates its brain to create the sense of different textures. Monkey think, monkey do, monkey feel – all without moving a muscle.
And this is where  Nicolelis wants to be in three years: a young quadriplegic Brazilian man strolls confidently into a massive stadium. He controls his four prosthetic limbs with his thoughts, and they in turn send tactile information straight to his brain. The technology melds so fluidly with his mind that he confidently runs up and delivers the opening kick of the 2014 World Cup.

This sounds like a far-fetched dream, but Nicolelis – a big soccer fan – is talking to the Brazilian government to make it a reality. He has created an international consortium called the Walk Again Project, consisting of non-profit research institutions in the United States, Brazil, Germany and Switzerland. Their goal is to create a “high performance brain-controlled prosthetic device that enables patients to finally leave the wheelchair behind.”


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How the miracle fruit changes sour into sweet

Pop a “miracle berry” into your mouth, and you might wonder if it was named by an overreaching marketing department. The small red fruit tastes of very little – it has a “mildly sweet tang… [like] a less flavorful cranberry”. But it’s not the taste of the fruit itself that matters. To understand why the berry gets its name, you need to eat something acidic. The berries have the ability to make sour foods taste deliciously sweet. Munch one, and you can swig vinegar like it was a milkshake, or bite lemons as if they were candy.

The secret to the fruit’s taste-transforming powers is a protein called miraculin. Now, Ayako Koizumi from the University of Tokyo has discovered just how the protein acts upon our tongues.


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The Alice Illusion – scientists convince people that they’re dolls or giants

"Show me on the doll where the neuroscientist touched you..."In Alice’s Adventures in Wonderland, the titular heroine quaffs a potion that shrinks her down to the size of a doll, and eats a cake that makes her grow to gigantic proportions. Such magic doesn’t exist outside of Lewis Carroll’s imagination, but there are certainly ways of making people think that they have changed in size.

There’s nowhere in the world that’s better at creating such illusions than the lab of Henrik Ehrsson in Sweden’s Karolinska Institute. In a typical experiment, a volunteer is being stroked while wearing a virtual reality headset. She’s lyng down and looking at her feet, but she doesn’t see them. Instead, the headset shows her the legs of a mannequin lying next to her.

As she watches, Bjorn van der Hoort, one of Ehrsson’s former interns, uses two rods to stroke her leg, and the leg of the mannequin, at the same time. This simple trick creates an overwhelming feeling that the mannequin’s legs are her own.  If the legs belong to a Barbie, she feels like she’s the size of a doll. If the legs are huge, she feels like a 13-foot giant.


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The brain on sonar – how blind people find their way around with echoes

Daniel Kish has no eyes. He lost them to cancer at just 13 months of age, but you wouldn’t be able to tell from watching him. The 44-year-old happily walks round cities, goes for hikes, rides mountain bikes, plays basketball, and teaches other blind youngsters to do the same. Brian Bushway helps him. Now 28 years old, Bushway lost his vision at 14, when his optic nerves wasted away. But, like Kish, he finds his way around with an ease that belies his disability.

Both Kish and Bushway have learned to use sonar. By making clicks with their tongue and listening to the rebounding echoes, they can “see” the world in sound, in the same way that dolphins and bats can. They are not alone. A small but growing number of people can also “echolocate”. Some develop the skill late in life, like Bushway; others come to it early, like Kish. Some use props like canes to produce the echoes; others, just click with their tongues.

The echoes are loaded with information, not just about the position of objects, but about their distance, size, shape and texture. By working with these remarkable people, scientists have worked out a lot about the scope and limits of their abilities. But until now, no one had looked at how their brains deal with their super-sense.


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Bad gossip affects our vision as well as our judgment

You’re chatting to some friends at a party and they point out someone standing in a different part of the room. That person, they inform you, is a nasty piece of work. He cheats on his girlfriend.  He picks fights with strangers. Once, he bit a puppy. You’d never seen him before but after this character assassination, you start noticing him everywhere – in other parties, on the street, on Facebook.

This sort of thing happens all the time. If we get information about people from third parties – gossip – we start paying more attention to those people. There’s a simple reason for this. Gossip, especially negative gossip, affects not only our judgment, but our vision too. It influences both what we think about someone and whether we see them in the first place.


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The Beeblebrox Illusion: scientists convince people they have three arms

“He relaxed and spread his two arms lazily across the seat back. He steered with an extra arm he’d recently fitted just beneath his right one to help improve his ski-boxing.” – Douglas Adams, The Hitchhiker’s Guide to the Galaxy

Zaphod Beeblebrox is just one of several characters from science-fiction and mythology to have extra arms. It’s a common enough trope, but would it actually work in real life? Could the human mind, which is so accustomed to controlling two arms, cope with a third or fourth one? According to Arvid Guterstam from the Karolinska Institute, the answer is yes. By placing a rubber right hand next to a person’s real one, and stroking both at the same time, Guterstam managed to convince people that they had a third arm.


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Tears as chemical signals – smell of female tears affects sexual behaviour of men

In an Israeli laboratory, Shani Gelstein is harvesting a woman’s tears. The volunteer is watching the end of the boxing film The Champ. As she weeps, she holds a vial under her eyes to capture the fresh drops. This might seem ghoulish, but Gelstein has used the collected tears to understand why people cry during emotional times. She thinks they’re a chemical signal.

Gelstein used several different techniques to show that the smell of a woman’s emotional tears could reduce a man’s sexual arousal. The men never actually saw anyone cry, and they didn’t know about what they were smelling. Even so, their sniffs reduced their testosterone levels and they lowered the activity in parts of their brain involved in sexual desire.


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Curb those food cravings by imagining yourself eating lots of food


Imagine that you’re eating your favourite food, perhaps a bloody steak or an obscenely large bar of chocolate. You’re probably quite keen for an actual mouthful now. You may even have started to salivate. But wait – before you dash for the kitchen, imagine eating another one. And another one. In fact, picture yourself guzzling down thirty more. Do you still want a bite?

If you had done this with actual food, the answer would probably be no. The more we expose ourselves to a something, the more we get used to it. This process, known as ‘habituation’, applies to all sorts of things – bright lights, level of wealth and, yes, the taste of food. The first bite of chocolate is heavenly but the fifteenth usually feels less so. Now, Carey Morewedge from Carnegie Mellon University has found that people habituate to the taste of food even if they just imagine themselves eating it.


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The size of your brain’s visual centre affects how you see the world


Look at the image above. Which of the central orange circles looks bigger? Most people would say the one on the right – the one surrounded by the smaller ‘petals’. In truth, the central circles are exactly the same size. This is the Ebbinghaus illusion, named after the German psychologist Hermann Ebbinghaus. It has been around for over a century, but it still continues to expand our understanding of the brain.

Samuel Schwarzkopf from University College London has just discovered that the size of one particular part of the brain, known as primary visual cortex or V1, predicts how likely we are to fall for the illusion. V1 sits at the very back of our brains and processes the visual information that we get from our eyes. It’s extremely variable; one person’s V1 might have three times the surface area of another person’s. While many scientific studies try to average out those differences, Schwarzkopf wanted to explore them.


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Newborn babies have a preference for the way living things move

Running_rabbitThis is an old article, reposted from the original WordPress incarnation of Not Exactly Rocket Science. I’m travelling around at the moment so the next few weeks will have some classic pieces and a few new ones I prepared earlier.

From an animal’s point of view, the most important things in the world around it are arguably other animals. They provide mates, food, danger and companionship, so as an animal gazes upon its surroundings, it needs to be able to accurately discern the movements of other animals. Humans are no exception and new research shows that we are so attuned to biological motion that babies just two days old are drawn to extremely simple abstract animations of walking animals.

Animals move with a restrained fluidity that makes them stand out from inanimate objects. Compared to a speeding train or a falling pencil, animals show far greater flexibility of movement but most are nonetheless constrained by some form of rigid skeleton. That gives our visual system something to latch on to.


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Your brain sees your hands as short and fat


Knowing something like the back of your hand supposedly means that you’re very familiar with it. But it could just as well mean that you think it’s wider and shorter than it actually is. As it turns out, our hands aren’t as well known to us as we might imagine. According to Matthew Longo and Patrick Haggard from University College London, we store a mental model of our hands that helps us to know exactly where our limbs are in space. The trouble is that this model is massively distorted.