Category: Perception

The smell of white – mixtures of many distinct scents end up smelling the same

By Ed Yong | November 19, 2012 3:00 pm

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

By Ed Yong | September 4, 2012 7:00 pm

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)

By Ed Yong | October 5, 2011 1:00 pm

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

By Ed Yong | September 26, 2011 3:00 pm

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

By Ed Yong | May 26, 2011 9:00 am

"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

By Ed Yong | May 25, 2011 4:18 pm

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

By Ed Yong | May 20, 2011 8:47 am

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

By Ed Yong | February 23, 2011 5:00 pm

“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

By Ed Yong | January 6, 2011 2:00 pm

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

By Ed Yong | December 9, 2010 2:00 pm

Cookie_monster

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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MORE ABOUT: food, habituation, imagine
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