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The First Time Oliver Sacks Saw Heaven (1964)

My friend Oliver Sacks was at home, hoping to glimpse the color of heaven. It was 1964. He was in his kitchen in Topanga Canyon, preparing a cocktail. It wasn’t an ordinary cocktail, being part amphetamine (“for general arousal,” he told me), part marijuana (“for added delirium”), and part LSD (“for hallucinogenic intensity”), and his plan was to gulp, wait … and then command heaven to appear.

A color portrait of neurologist and author Dr. Oliver Sacks
Portrait of Oliver Sacks, Photograph by Joost van den Broek, Hollandse Hoogte, Redux
Portrait of Oliver Sacks, Photograph by Joost van den Broek, Hollandse Hoogte, Redux

Oliver was not a believer. I’m sure he didn’t imagine a heaven with white clouds and angels darting about. White wasn’t his color. If heaven existed, he thought it would be bluish—not a pale blue, but “true indigo,” a rich, intense, deep blue that he had never seen. Nor had anyone. The great painter Giotto had tried to paint heaven in indigo. He worked with a number of powders but hadn’t found the right formula. Oliver imagined it to be an “ecstatic blue,” bluer than the lapis lazuli stone favored by the ancient Egyptians, a blue inspired by the seas of the ancient Paleozoic (“How do you know that?” I asked. “I just do,” he said). He wanted, desperately, to see it.

This was a brazen desire. True indigo is the unicorn of colors, maybe hidden from us, Oliver thought, “because the color of heaven was not to be seen on Earth.” But he would try.

He swallowed his cocktail. He waited for 20 minutes. Then he turned to a blank white wall in his kitchen and shouted (“To whom?” I asked. “Eternity,” he said), “I want to see indigo now—now!”


All of a sudden “as if thrown by a giant paintbrush,” Oliver remembers that a “huge, trembling, pear-shaped blob” of color appeared magically on the kitchen wall. It was a miracle of blue. It was, he says, “luminous, numinous; it filled me with rapture.” It stayed in place for a very little while, and then, just as suddenly, vanished.

Where Have You Gone?

Come. Gone. He looked around, puzzled, as if his prize had been “snatched away,” and yet … he had seen it. He knew that, “yes, indigo exists, and it can be conjured up in the brain,” and having had a first “sip,” as he called it, he eagerly wanted more. So he went hunting. He visited museums, walked beaches, looked at gems, at shells. One time, at the Metropolitan Museum of Art, he got another very short glimpse in the sheen of an Egyptian jewel, but when he turned away and then looked back, he found only “blue and purple and mauve and puce—no indigo.”

That was 50 years ago. He never saw indigo again. Unless (and I can’t help thinking this), now that he’s left us, (Oliver died this week), he may be up there floating in an indigo-rich Paleozoic sea, surrounded not by angels but by pale blue cuttlefish, his favorite cephalopods. And looking up at him, winking quietly, I see a small crab, very much alive, that may be the only creature on Earth to experience Oliver’s favorite color all the time. I recently made this discovery (that heaven may be hiding here) in a poem by Mark Doty.

I wish I’d shown this to Oliver. A few years ago, Mark came upon a half-eaten crab on a beach somewhere, turned over its shell, peeked inside, and saw this:

an overturned crab shell lying on rocks reveals the beautiful indigo color inside
Photograph by Gregory Wake, Flickr

A Green Crab’s Shell, by Mark Doty

Not, exactly, green:
closer to bronze
preserved in kind brine,

something retrieved
from a Greco-Roman wreck,
patinated and oddly

muscular. We cannot
know what his fantastic
legs were like—

though evidence
suggests eight
complexly folded

scuttling works
of armament, crowned
by the foreclaws’

gesture of menace
and power. A gull’s
gobbled the center,

leaving this chamber
—size of a demitasse—
open to reveal

a shocking, Giotto blue.
Though it smells
of seaweed and ruin,

this little traveling case
comes with such lavish lining!
Imagine breathing

surrounded by
the brilliant rinse
of summer’s firmament.

What color is
the underside of skin?
Not so bad, to die,

if we could be opened
into this—
if the smallest chambers

of ourselves,
revealed some sky.

Mark Doty’s poem comes from his collection, Atlantis, published in 1995 [published by HarperCollins. Copyright © 1995 by Mark Doty.] Oliver Sacks wrote about his search for indigo in his book Hallucinations and we talked about it together on “Radiolab.”

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Do You Have a Face-Finding Superpower for Fighting Crime?

At a crowded tourist site, a young man in a yellow T-shirt angles for a spot on a bench. He sits, removes his backpack, and places it on the ground. After riffling through a blue plastic shopping bag, he walks away, leaving the backpack behind. A few minutes later, a bomb explodes. Twenty people die.

All that’s known about the young man in the yellow T-shirt is contained in a snippet of dim, grainy footage from a CCTV camera. Would anyone recognize his face?

This really happened. Just a couple weeks ago, Thai police launched a search for the young man in a yellow T-shirt, whom they believe blew up Bangkok’s Erawan shrine on August 16. They arrested a man at the Cambodian border and say he matches the description of the yellow-shirted bomber. But based on that grainy footage, they hesitate to say for sure.

Photograph by REUTERS, Thai Police/Handout via Reuters
This man was spotted dropping a backpack just before the bombing of a Bangkok shrine. Photograph by REUTERS, Thai Police/Handout via Reuters
Police captures this image of a man in a yellow shirt dropping a backpack just before the bombing of a shrine in Bangkok.

It’s just this kind of situation that prompted Scotland Yard to form a team of super-recognizers.  These London police officers have an amazing ability to recognize and match faces, even from rough CCTV footage. 

“Gary Collins is so good that he ID’d three people over his Sunday roast,” says Detective Chief Inspector Mick Neville, speaking about one member of the super-recognizer team who likes to relax on weekends with an iPad loaded with photos of criminal suspects. After London’s 2011 riots, the superrecognizers combed through thousands of hours of footage; Collins alone identified an incredible 190 faces among the rioters. Today, Neville heads London’s central forensic image team, which has tested thousands of police officers and identified 152 super-recognizers. These face-spotting stars normally work in their local stations, building up a mental library of the area’s criminals, and periodically attach to New Scotland Yard to solve crimes.

So far, among their wins they’ve helped to solve the murder of 14-year-old Alice Gross, spotted a serial molester on different city bus routes (he was tracked to particular routes and arrested) and are now working to link at least 30 different thefts, including major art and jewel heists, to one perpetrator.    

London’s super-recognizers were out in force at this week’s Notting Hill Carnival, the world’s biggest street fair outside Rio de Janeiro. “We’ve had a lot of problems with crime at the carnival,” Neville says. So super-recognizers sat in CCTV control centers this year and scanned the crowd, where they spotted members of rival gangs edging close to one another. Officers on the scene found and disarmed the men, averting a potential fight. “The senior detective was amazed at their ability to spot suspects in dense crowds,” Neville says.

You might share this superpower, too, and not even know it. The ability to recognize faces, it turns out, falls along a spectrum, says David White of the University of New South Wales’ forensic psychology laboratory. At the lowest end are people who are “face-blind,” a condition called prosopagnosia. (Oliver Sacks, the famous neurologist who recently died, had this condition. He said he recognized his best friend Eric by his “heavy eyebrows and thick spectacles.”) On the other end are super-recognizers.

Most people overestimate their skills, White says. “When people think of face recognition, they think of recognizing people they know,” he says—like spotting a friend in the grocery store. But recognizing the face of a stranger, say from two different photos laid side-by-side: That’s much, much harder.

You can take a test to get an idea of where you fall on the spectrum. Josh Davis, a psychologist at the University of Greenwich, devised both a short, simple test—meant as an extremely rough first pass for fun—and a more detailed test that will help researchers map out how many people fall along each part of the spectrum.  (Go here to take the simple test and find a link to the longer test.)

So far, Davis says, it appears that face recognition is an innate ability—not learned, for the most part—and that it’s distributed on a bell curve, like IQ. No particular genes have been linked to the ability, but a 2010 study found that face-recognition ability was very similar in identical twins, compared with fraternal twins, a first indicator of a genetic link to this skill. What’s more, prosopagnosia or “face-blindness” is tied to the fusiform face region, slivers that run along the bottom of the brain near the back of your head. That’s probably a good place to look for evidence of differential brain activity in super-recognizers as well.

London's police super-recognizers identified Arnis Zalkalns as the potential killer of Alice Gross based on CCTV images. Photograph courtesy of Metropolitan Police/PA Wire
London’s police super-recognizers identified Arnis Zalkalns as the potential killer of Alice Gross based on CCTV images. Photograph courtesy of Metropolitan Police/PA Wire

So what percentage of people might be super-recognizers? Davis says that depends where you decide to draw the line, but certainly fewer than 1 percent of people fall into the tail end of the bell curve where the truly exceptional lie.

Next is the question of how to take advantage of people with natural face-sighting superpowers. Detective Neville says that he’s had phone calls from police around the world interested in learning about his team. And White has been working with the Australian passport office to develop tests for face-matching ability and training for passport officers, who in their day-to-day work have to determine whether the stranger in front of them is the same person shown in a tiny passport photo.

In a study published Tuesday in the Proceedings of the Royal Society B, White’s team tested a group of crack forensic examiners who specialize in face image analysis to see whether they would perform better than average, and to begin understanding whether training might help to improve the skills of people who match faces for a living.

The experts, it turned out, did perform better than either untrained students or forensic experts who don’t match faces regularly. (And, by the way, did far better on tasks where facial-recognition computer algorithms typically fail.) Perhaps people with above-average skills gravitated into these positions based on their abilities. But surprisingly, the expert face-matchers showed another ability, unusual in those with “natural” face-matching skills, to identify faces that were shown upside-down. That suggests to White that the experts’ training, which emphasized breaking a face down into component parts and matching each one, may be boosting their skills beyond their natural abilities.

So perhaps there’s still some hope for those who, like me, score a pathetic 7 out of 14 on the simple face-matching test.

A bit murkier, though, is how courts around the world might respond to the introduction of evidence based on a positive ID by a super-recognizer. In the United States, judges use a legal precedent called the Daubert standard to determine whether  evidence is scientifically supported, and eyewitness IDs of all sorts have come under scrutiny. But Neville says his team’s matches are usually just the starting point for developing a criminal case, pointing police toward a suspect who can then be investigated using DNA or good old gumshoe police work, in which case the ID is more of an investigative tool than direct evidence of criminal misdeeds.

Meanwhile, the Thai police say they’re looking for more eyewitnesses in the case of their suspected bomber, and say they will “perform further tests related to existing evidence, such as fingerprints, DNA, and photos.”

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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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Surgeon Reveals Head Transplant Plan, But Patient Steals the Show

ANNAPOLIS, Md.—Valery Spiridonov looks impossibly small. He is dressed in all white, from his white button-down shirt to the white socks on his feet, which dangle at the ends of white pants and a white blanket. Breaking up the look is a black strap, which holds him to a motorized wheelchair.

He uses his left hand, which he can still move, a little bit, to steer the wheelchair into a hotel meeting room. There, he confirms that he would like to be the first person ever to have his head transplanted onto a new body.

Spiridonov flew from Russia to be at this conference, the American Academy of Neurological and Orthopaedic Surgeons (AANOS). He joined the surgeon proposing to do the transplant, Sergio Canavero of Turin, Italy. Canavero had built up his talk, a keynote address, for months, promising a big reveal of his plans to transplant Spiridonov’s head onto a donor body. (For background, see my earlier blog post and a good overview at New Scientist.)

The meeting is small, maybe 100 or fewer surgeons, and held in a very normal-looking Westin hotel in Annapolis, Md. Conference organizer Maggie Kearney spent much of the day turning away reporters in anticipation of a packed room. She says that in 15 years, she can’t remember a reporter ever attending the surgical conference before.

By the end of Canavero’s three-hour-long presentation (it was supposed to be an hour and a half, Maggie tells me), most of the reporters in the room seem worn out, and a bit confused about what the fuss was all about.

Sergio Canaveros
Sergio Canaveros, right.
Erika Engelhaupt

Canavero reviewed, at length, the scientific literature on spinal cord injury and recovery, regrowth of various parts of the central nervous system, and why some of the basic assumptions of neurosurgery are wrong. Throughout the lecture, he would occasionally point to Valery Spiridonov, his wheelchair parked near the stage, and make a declaration (“Propriospinal tract neurons are the key that will make him walk again!”).

Answering detractors’ comments that the transplant could be “worse than death” or could drive Spiridonov insane, Canavero asked Spiridonov directly, “Don’t you agree that your [current] condition could drive you to madness?”

Spiridonov answered quietly in the affirmative.

His condition is grave: a degenerative motor neuron disease that is slowly killing him. “I am sure that one day gene therapy and stem cells will fulfill their future,” Canavero said, “but for this man it will come too late.”

Finally, near the end of the talk, Canavero roughly outlined the surgery. He plans to sever the spinal cord very cleanly, using a special scalpel honed nano-sharp. (I could not see Spiridonov’s reaction to the special scalpel, but wondered.)

To minimize any die-off of cells at the severed ends during the transfer, Canavero says he will cut Spiridonov’s spinal cord a bit lower on the spine than needed, and the body’s a bit higher, and then at the last minute slice them again for a fresh cut. Then, add some polyethylene glycol (shown to stimulate nerve regrowth in animals), join the two ends together with a special connector, and voila. Electrical stimulation would then be applied to further encourage regrowth.

Of course, there’s a bit more to it, like reconnecting all the blood vessels and so forth, but Canavero is a neurosurgeon and the spinal cord was his focus.

Other neurosurgeons at the meeting responded cautiously to the proposal. The surgery might be possible “someday, but it is really a delicate situation,” said Kazem Fathie, a former chair of the board of AANOS.

Craig Clark, a general neurosurgeon in Greenwood, Mississippi, calls Canavero’s idea “very provocative.”

“There have been many papers over the years that have shown regeneration, but for one reason or another they didn’t pan out when applied clinically,” he said.

“There’s a lot of ethical questions about it,” said neurosurgeon Quirico Torres of Abilene, Texas. But Torres thinks it could be ethical to allow volunteers to do the surgery, and one day we might consider it normal. “Remember, years ago people were questioning Bill Gates: why do you need a computer? And now we can’t live without it.”

What’s Next?

Apart from the rundown of previous work on spinal cord injury, much of what Canavero said about the surgery was pretty much what he has said before. He supported his arguments for individual elements of a head transplant (or body transplant, if you prefer) but did not reveal any new demonstration of the entire procedure working in a person or an animal.

But Canavero has no shortage of confidence. He says he wants to do the surgery in America (implying Italy doesn’t have its act together enough to host a cutting-edge project like this).

“I have a detailed plan to do it,” he said, adding that he is asking Bill Gates and other billionaires to donate. He invited surgeons at the meeting to join his team, which could be enormous—more than 100 surgeons, he has said—and he wants team leaders in orthopedics, vascular surgery, and so on. These surgeons should work on the project full time for the next two years, he said, “and you will be paid through the nose, because I think doctors involved in this should be paid more than football players.”

Valery Spiridonov entering the conference room. Photo: Erika Engelhaupt

After the talk, Spiridonov disappeared into a room to rest. When he came back out, he answered questions for the TV crews that had descended, sounding a bit weary of answering the same questions he’s been asked before. “What will happen to you if you don’t get this surgery?” a reporter called out. “My life will be pretty dark,” he said. “My muscles are growing weaker. It’s pretty scary.”

He looked tired.

During his interviews, I stepped aside to talk with his hosts in Annapolis, who are friends of a friend of the Spiridonov family. “He’s brilliant, he’s happy, he’s funny,” said Briana Alessi. “If this surgery were to go through and if it works, it’s going to give him a life. It’s life-changing. He’ll be able to do the things he could only dream of.”

And if not? “He’s taking a chance either way,” she said.

The final question he takes from the press: What do you say to people who say this surgery should not be done?

Spiridonov’s reply: “Maybe they should imagine themselves in my place.”

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Now We Know What It Feels Like to Be Invisible

First, Arvid Guterstam made himself invisible. When he looked down at his body, there was nothing there.

He could feel he was solid; he hadn’t vanished into thin air. He even felt a paint brush tickle his transparent belly, while the brush appeared to be stroking nothing but air.

Being invisible is “great fun,” Guterstam reports, “but it’s an eerie sensation. It’s hard to describe.”

Then he took off his virtual reality headset and was back in the laboratory, fully visible. Guterstam is a medical doctor and PhD student, and he had just pulled off the first fully convincing illusion of complete invisibility. He went on to test 125 other people, and reports Thursday in Scientific Reports that seven out of ten also felt the illusion, and it was realistic enough to make them feel and respond physically as if a group of people could not see them.

One day, just maybe, cloaking devices might make human invisibility possible. Guterstam wants to know what that will feel like—and what these people might do. How about their morals? If you take away the chance of being caught, will people, as we might suspect, lose their sense of right and wrong?

But before he can test the moral fortitude of the newly transparent, Guterstam has to get people to feel completely invisible. He and his colleagues in Henrik Ehrsson’s laboratory at Sweden’s Karolinska Institute have succeeded at many other body-morphing illusions, including making my Phenomena colleague Ed Yong feel in turn that he had left his body, shrunk to the size of a doll, and grown a third arm.

They already convinced people they had an invisible hand. But what about the whole body? “This is definitely pushing the boundaries of how bizarre an illusion of this kind can get,” Guterstam says.

Gustav Mårtensson
A simple trick creates the illusion of an invisible hand. Gustav Mårtensson
A simple trick creates the illusion of an invisible hand.

This time, they had people put on a virtual-reality headset that showed the view from a second headset, mounted at head height on nothingness. If you were in this getup, a scientist would touch you with a paint brush while simultaneously touching the nothingness in the same place, as though a body were there. So as you felt the brush, your eyes would be telling you that the brush was touching your nothingness body.

When a scientist swiped a knife toward the invisible belly, people’s heart rates went up and they broke out in a sweat, the classic stress response. When put in front of an audience of serious-looking people staring them down, “visible” people also got stressed. But the “invisible” people—not so much. They felt so completely invisible that their bodies responded as though they really were invisible. Since the audience couldn’t see them, there was no reason to feel uncomfortable.

The illusion works because, as the team has learned from these tricks, it’s shockingly easy to create an out-of-body experience. Our sense that we reside within our bodies—what we can think of as our sense of self—is not fixed. Instead of being firmly locked in our body, our sense of self can float free, as if on a tether.

Our brains, it appears, create this body sense moment by moment, continuously monitoring our senses and putting the “me” where those senses say it should be. Move the senses, and you move the me. All it takes is creating a mismatch between where I see I’m being touched and where I feel it.

This is all very interesting, but what do we do with it? Well, Ehrsson’s group is also working on better prosthetic devices for amputees, that would harness the sense of self to make the prosthetic feel like a true body part. One day, we might even control robots with our movements and actually feel that we’ve jumped into the robotic body.

And then there’s the dream of actual invisibility, with all its moral dilemmas. For now, we don’t need to fret too much: The closest we’ve gotten is disappearing a cat and a goldfish, and only behind a fixed cloaking device and from the right angles.

All this talk of invisibility leads, inevitably, to The Question. A question whose answer, many believe, says something deep about each of us. If you could be the only person on Earth with a superpower, and you could choose between flight and invisibility, which would you choose?

Flight, many feel, is the noble choice. Invisibility is for thieves and perverts. Yet when we’re honest with ourselves, that’s exactly what many of us are, so invisibility maintains its secret allure.

And Arvid Guterstam? “I would probably say flying,” he says.

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Through This Chemical Loop, Dogs Win Our Hearts

Wolves are wild, powerful, and fearsome predators, capable of bringing down even large prey. And yet, tens of thousands of years ago, some wolves started forming close associations with humans. They became more docile. Their bodies changed. They turned into domestic dogs. Today, we share bonds with them that can be as strong as those that tie us to other people. How did this happen? How did we go from fear to friendship? How did dogs start inspiring such genuine feelings of love and affection?

Miho Nagasawa at Azabu University, Japan has a possible answer. It involves oxytocin, a mammalian hormone that draws our attention to social cues. In yesterday’s post, I described mouse experiments which show how oxytocin sensitises an inexperienced mother to the distress calls of her pups, and eventually cements the bond between them. Dogs seem to have hijacked this chemical connection between mother and child, to cement a similarly strong bond with their owners.

Nagasawa showed that a dog’s gaze raises the oxytocin levels in its owner, prompting more social contact. In return, the owner’s gaze raises oxytocin levels in the pooch. This chemical loop unites the brains of two different species. “[It’s] a powerful mechanism through which dogs win our hearts—and we win theirs in return,” write Evan MacLean and Brian Hare from Duke University, in an accompanying editorial.

First, Nagasawa allowed thirty dog owners to interact with their animals for half an hour. She collected urine samples from both parties before and after that period, so she could measure the oxytocin levels in their bodies.

She found that the volunteers whose dogs gazed at them for the longest time experienced the biggest surges in oxytocin. They, in turn, spent more time looking back at their dogs, touching them, and talking to them. And the dogs that received the most reciprocal attention also experienced the biggest oxytocin spikes. Nagasawa had already shown the dog-to-human part of this loop in 2009 but she has now closed it, demonstrating that both species raise oxytocin levels in each other.

The same can’t be said for wolves. Nagasawa did the same experiment with eleven pure-bred wolves that were hand-reared by people. They weren’t pets, but they did have daily contact with their owners, who fed them and occasionally played with them. Despite their dog-like existence, these wolves did not make regular eye contact with their owners, and their gaze didn’t trigger a rise in oxytocin. The cross-species oxytocin loop only works between humans and domestic dogs.

Next, Nagasawa injected 27 dogs with oxytocin and placed them in a room with their owner and two strangers. After the injections, the dogs—but only the female ones—spent more time gazing at their owners, who then experienced a rise in oxytocin. It’s not clear why only the female dogs responded in this way. They might be more sensitive to the hormone, or less wary about the presence of unfamiliar people. Whatever the case, this second experiment confirmed that an oxytocin spike in one species can trigger a similar spike in the other.

These results offer important clues about the events that transformed wild wolves into domestic dogs. “During dog evolution, we have probably selected for a behaviour in dogs that elicits a physiological response in us that promotes bonding,” says Larry Young from Emory University. “That behaviour is eye-gazing.”

Among wolves, eye contact is a threat, which is why they rarely look directly at each other. Young suspects that wolf pups might communicate with their mothers through looks, triggering the same kind of affectionate cycle that exists in humans. “This just goes away as they mature,” he speculates. Perhaps as wolves evolved into dogs, they simply kept this child-like means of communication, just as they also retained some of the physical traits of their younger selves. In this way, they could have tapped into the oxytocin loop that strengthens bonds between human mothers and their babies, and triggered an almost parental affection.

Indeed, brain-scanning experiments have shown that there are overlaps in the brain regions that become active when human mothers look at images of their children or their dogs. “Diverse aspects of our biology appear to be tuned into dogs and children in remarkably similar ways,” write MacLean and Hare.

Reference: Nagasawa, Mitsui, En, Ohtani, Ohta, Sakuma, Onaka, Mogi & Kikusui. 2015. Oxytocin-gaze positive loop and the coevolution of human-dog bonds. Science http://dx.doi.org/10.1126/science.1261022

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Oxytocin Makes New Mouse Mothers Focus on Cries of Lost Pups

Infant mice are born blind, deaf and vulnerable. They spend their early lives snuggled under their mothers, barely moving. If mum is forced to move nests, the pups cling to her fur. And if they fall off, as often happens, they make distinctive high-pitched distress calls. When virgin females hear these calls, they ignore them. Experienced mothers, however, will always head back to retrieve their lost youngsters. Something changes their brain during their first forays into motherhood, turning these unimportant calls into irresistible cries.

That something is a hormone called oxytocin. Bianca Marlin from New York University have shown that when virgin females get a boost of oxytocin, they readily retrieve crying pups, just like experienced mothers. The hormone specifically affects a part of their brain that deals with sounds. It tunes the neurons there to make the cries of lost pups more “socially salient”. These sounds now grab attention, just like a name being spoken across the room in a loud party. Oxytocin makes them pop.

This is far from the first study to show that oxytocin plays an important part in the social life of mammals. The substance is released during labour and strengthens bonds between mothers and children. It also cements the connections between monogamous voles. For these reasons, oxytocin often gets plastered with trite and misleading names, like “hug hormone” or “moral molecule”. It is nothing of the sort. Although some psychological studies have found that it promotes trust, empathy, and co-operation, others have shown that it can foster envy, schadenfreude, favouritism, and distrust in different situations.

Rather than virtue incarnate, oxytocin is more of an all-purpose social molecule. It probably acts as a spotlight that draws our attention to social cues. We then react differently, depending on our temperament, or whether those social cues are positive or threatening.

That’s a more nuanced view of this much-hyped molecule, but it’s still a bit unsatisfying. As I wrote in 2012, “the problem with oxytocin research is that too many people have been focusing on cataloguing what it does… rather than how it works.” There’s been a lot of psychology and much less hard neuroscience. Thankfully, things are changing. Several teams of scientists are looking past the alliterative nicknames and actually working out how oxytocin affects neurons.

Marlin started by finding exactly where oxytocin exert its influence in the brain. The hormone works by attaching to a receptor protein, like a cable plugging into a socket. Marlin’s colleagues created an antibody that stick to the socket, revealing its presence. It turned out to be especially common in a mouse’s left auditory cortex—a region in the left side of their brain that processes sounds. If Marlin injected oxytocin into this area, or stimulated the local neurons to release the hormone themselves, she could turn negligent, inexperienced females into doting, pup-retrieving ones.

That result was surprising, says Robert Liu from Emory University, because no one had really linked this part of the brain to oxytocin before. And “it’s surprising that just putting oxytocin in that region could lead to the behaviour,” he adds. Then again, “it’s only in the last few years that people have really started looking at where and how oxytocin is acting on neurons.”

Marlin had the ‘where’ bit. To understand the ‘how’, she used electrodes to record the activity of individual neurons in the auditory cortex, to work out how they react to oxytocin. She found that the hormone strengthens excitatory signals that rouse neurons into a buzz of activity, while also suppressing inhibitory signals that would otherwise shush them into silence. This creates a window of time in which the auditory cortex becomes much more responsive to incoming information—in this case, the distress calls of pups.

Robert Froemke, who led the study, explains that the auditory cortex filters the sounds we hear, so that we can pay attention to the ones that matter. That’s why we can listen to a single person in a loud bar, or ignore the ticking of a clock at home. “In the naive virgin mice, the auditory cortex throws away the pup calls,” Froemke says. But when oxytocin hits, those once-ignored calls start to stand out.

“They seem to have shown that oxytocin transforms an otherwise irrelevant stimulus into one that grabs my immediate attention and requires my immediate action,” says Jennifer Bartz from McGill University. “It increases attention not only to social cues but also to their personal significance.”

The neurons of the auditory cortex also started responding to pup calls more consistently and synchronously. “If the neurons are firing disjointedly, they cancel each other out and create a lot of noise,” says Larry Young from Emory University. “This paper suggests that oxytocin causes these neurons to fire with perfect timing, amplifying their response to the pups’ calls.” Again, this makes the mother more attentive.

This only needs to happen once. Once the mums start paying attention to the distress calls, they can then retrieve their pups without any further pulses of oxytocin. They don’t continually need the hormone to be good parents. They just need it to initially point their brains at the right stimuli. “It may be learning or it may be unlocking an instinct,” says Froemke. “It’s not really clear what’s going on there.”

He now wants to know what triggers the initial burst of oxytocin that changes the brains of inexperienced females. Also, once oxytocin changes the brain, how does that lead to the actual act of retrieving a pup? Finally, does oxytocin affect other senses too? Does it make mothers more sensitive to the smell of babies, or to their touch? And what about humans and other animals? “In people, visual cues are important,” says Young. “Is this kind of thing happening in areas that process visual information?”

Young praises Marlin and Froemke’s work. “They have delved deep into the neural mechanism, more than anyone else has done,” he adds. “This kind of study, which gets into details and doesn’t attribute fluffy psychological traits to this molecule, is exactly what we need to move the field forward.”

Reference: Marlin, Mitre, D’Amour, Chao & Froemke. 2015. Oxytocin enables maternal behaviour by balancing cortical inhibition. Nature http://dx.doi.org/10.1038/nature14402

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The Wisdom of the Fly Crowds

Few animals have been more thoroughly studied than the fruit fly Drosophila melanogaster. Scientists have sequenced its genome, tracked its development from single cell to fully-formed fly, and teased apart the neurons in its brain. They know this fly at the most intimate level, but for all that knowledge, they’ve been operating under one false assumption: that it’s a loner. Drosophila is classified as a solitary species.

“The conventional wisdom in the field was that flies are solitary animals that probably make decisions independently of one another,” says Pavan Ramdya from the University of Lausanne. “But if you watch them in your compost pile or fruit basket, you’ll notice that they often form groups when eating, seeking mates, or laying eggs.”

When animals live in groups, they can unlock incredible behaviours just by interacting with their neighbours according to simple rules. Locusts can form crop-devastating, sun-blocking swarms; starlings can form beautiful murmurations; fish can solve problems as a shoal. Ramdya suspected that the supposedly anti-social flies might also show collective behaviour.

He was right. Through a impressive series of experiments, involving a smorgasbord of cutting-edge techniques, Ramdya showed that flies can collectively flee from a bad smell faster than any individual can by itself. Alone, each fly is only slightly repelled by the odour; together, they run away decisively. Even mutant flies that can’t smell the odour at all can escape if they’re in the presence of smell-sensitive peers.

“It’s a scenario familiar to any big city dweller,” says Leslie Vosshall from Rockefeller University, who studies the senses and nervous systems of insects. “Pushy crowds respond to bad things differently than individual people, because information can flow through the group that compels it to act. It turns out flies are exactly like people in this regard.”

Ramdya first put flies in an arena, half of which had been flooded with carbon dioxide, and used an automatic tracking system to record their movements. Flies supposedly avoid carbon dioxide but isolated insects didn’t seem to care. But as Ramdya added more and more flies, their decisions improved, and they started to rapidly move towards the fresh-air side.

These collective movements are borne of three incredibly simple rules. First, an individual fly walks a little more often when exposed to carbon dioxide, but not in any particular direction. Second, if it moves from fresh air to carbon dioxide, it turns around. Third, if another fly bumps into it, it walks away from the bumper. For a single fly, these rules mean a lot of aimless walking. But in a group, flies that smell carbon dioxide end up bumping their neighbours out of the smelly zone. That’s what Ramdya saw in real life, and he even managed to reproduce the same effect in a computer simulation, by programming virtual flies to obey the same rules.

Even flies that couldn’t smell carbon dioxide ended up in fresh air. “It’s as if the smell-blind flies are milling around oblivious to the bad news, until they are jostled by the normal flies heading for the exits,” says Vosshall.

The flies don’t respond to any old bump. When Ramdya touched them with a small metallic disc, “they would simply shift their legs as if they were annoyed”. They only walked when he lightly grazed the tips of their legs. Only the gentlest of touches would do.

Ramdya even identified the exact neurons in the flies’ legs that drive their group behaviour. He engineered several strains of flies that each produced a nerve-paralysing toxin in a different set of touch-sensitive neurons. One particular strain stopped walking when bumped by its neighbours. Their silenced neurons made them behave like loners, even when they were surrounded.

Ramdya took these flies and swapped the toxin out for a glowing green protein, to label the neurons that had previously been deadened. He then proved that these cells were driving the flies’ collective behaviour by loading them with a light-sensitive protein—he could then make the neurons fire on demand by flashing them with blue light. When he did this, the flies went for walks as if they’d been bumped.

“This is a landmark study of collective behaviour,” says Iain Couzin from Princeton University and the Max Planck Institute for Ornithology. “Never before has it been possible to unweave the intricate coding of social behaviour during collective decision-making.” When it comes to fruit flies, scientists have so many tools and techniques at their disposal that they can really start to understand the origins of collective behaviour—how genes in the fly’s neurons are activated, how those neurons process signals from the fly’s environment, and how they drive individual behaviours that, in turn, lead to swarm behaviour. This is the future of the field, and one that I hinted at in my piece for Wired.

The flies also provide a great example of wisdom of the crowds—where groups make better decisions than individuals. For example, if you ask people to guess the number of beans in a jar, individuals might be wildly out but the average of their guesses will be uncannily accurate. Similarly, each fly imperfectly reacts to the odour, but via simple touches, they can pool their imperfect behaviour and head in the right direction.

A similar process goes on in your head. The 86 billion neurons in the human brain are individually unthinking, and interact with their neighbours according to very simple rules. But together, they can land machines on passing comets, craft works of astonishing beauty, and even unravel the collective behaviours of other creatures.

Reference: Ramdya, Lichocki, Cruchet, Frisch, Tse, Floreano & Benton. 2014. Mechanosensory interactions drive collective behaviour in Drosophila. http://dx.doi.org/10.1038/nature14024

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It’s Behind You! Robot Creates Feeling of Ghostly Presence

There was someone behind her; she was sure of it. A malignant presence: always a man, and always to her right. But whenever she looked around, he was gone.

It was 2006. The woman was in University Hospital, Geneva, awaiting surgery to remove parts of her brain that were causing epileptic seizures. The surgeons, led by neurologist Olaf Blanke, prepared for the operation by electrically stimulating her brain, to identify important regions that they needed to preserve. When they shocked one specific area—the left temporoparietal junction—she immediately felt a phantom menace behind her.

She turned to look and when Blanke asked her why, she said that she felt a “shadow” behind her, silent and still. She did the same thing every time the team stimulated the same region. “It was so real,” says Blanke. “She wasn’t convinced by us telling her that it wasn’t real.”

This sort of feeling isn’t new. Since time immemorial, humans have traded stories about ghosts and wraiths—haunting presences that are strongly felt but never seen. Mountaineers often report feeling an unseen presence keeping in step beside them. And many people with neurological or psychiatric problems have reported similar sensations. Blanke was seeing the same phenomenon at work in his patient, but with one critical difference: he could turn it on and off.

His team asked the woman to change position. She laid flat on the bed or sat up, holding her knees. In each case, the phantom assumed the same posture. That was a huge clue. Blanke suspected that her brain was somehow misplacing her sense of self.

That’s an odd concept. As you read this, you know that you are located inside your own body—a feeling so ingrained that it seems facile and absurd to even state it. But it turns out that your brain continuously constructs a feeling of body ownership, and that this seemingly hard-wired sensation is actually rather brittle. Scientists can easily disrupt it through simple illusions, which convince people that they’ve swapped bodies with a partner or are having an out-of-body experience. Blanke wondered if he could develop an illusion that could make a healthy person feel a ghostly presence.

Together with Giulio Rognini, a biomedical engineer from the EPFL in Switzerland, he designed a set-up involving two robots—a master that sits in front of a volunteer, and a slave that sits behind. You stick your right index finger in the master and move it around. These movements are sent to slave, which prods you in the back, using the same pressure, timing, and pattern. Meanwhile, the master also gives you tactile feedback through your fingertip. As a result, you feel that you’re stroking your own back, even though your arm is stretched out in front of you.

It’s a neat trick. But things got really interesting when the team added a short delay—a half-second difference between the volunteers moving the master, and the slave prodding them in return.

Suddenly, five participants felt that there was someone in the room, standing behind them and touching them—the same feeling that Blanke’s patient had. This is the first time that anyone has been able to deliberately recreate that feeling in a lab.

Now, you could argue that someone actually was standing behind them and touching them—the slave robot! But the volunteers all saw the set-up and they all knew about the robots. That didn’t matter; they genuinely and strongly felt that there was an actual person in the room with them, prodding them in the back. And it was a totally different feeling than when the master and slave robots were moving in sync.

The mismatched sensory and motor information confused their brains. If I prod myself in the chest right now, I can feel my joints moving, see my finger hitting my sternum, feel my chest through my finger, and feel my finger through my chest. Everything agrees, and I know that I’m inside my body. If those bits of information didn’t match up, my brain would revise its perception of reality to account for the discrepancies. Maybe I’m not inside my body at all, it might think. Maybe I’m over there.

Blanke suspects this is what happens in his volunteers, when they fall for the illusion. Their brains create two representations of their bodies: a strong one in the usual place, and a weaker one behind them. It’s a partial out-of-body experience.

The team found support for this idea by asking the volunteers to imagine throwing a ball to the opposite wall, and holding a button for as long as the ball is in the air. This simple task measures where the volunteers think they are. If they hold the button for a longer time, it’s because they intuitively feel that they’re further back in the room. And sure enough, the people who felt a strange presence held the button for longer than those who didn’t.

Blanke now wants to scan the volunteers’ brains to see what happens when they fall for the illusion. He has some hints already, through studying 12 people who had suffered from brain damage and regularly felt an unseen presence. All of them had damage to the same three parts of the brain: the insula, the frontoparietal cortex (FPC), and the temporoparietal cortex (TPC). Of these, only the FPC seems to be specifically damaged in people who feel a presence, and not in those who experience other types of hallucination.

This makes sense. These areas are involved in combining information from our senses and our movements, and in controlling our bodies. And other scientists have found that people who fall for body ownership illusions have stronger activity in these same areas. “It makes sense that lesions in these areas could lead to a breakdown in the normal integration of bodily signals,” says Henrik Ehrsson from the Karolinska Institute, who also studies body ownership. “Sensory information gets misplaced in space, leading to the feeling of a presence.”

These kinds of mismatches might occur spontaneously. Blanke thinks this is why so many mountaineers have experienced a presence beside them. “You’re exhausted. You have low oxygen. You don’t see anything except white and grey, and you just put one foot in front of another again and again,” he says. “So, you have a brain in an altered state of consciousness and also a robot-like repetitive state of motion.” There’s a lot of potential for the sensory and motor information in your brain to slip out of sync.

It’s possible that social isolation and extreme stress might so something similar, which might explain why people often see apparitions in times of loneliness or anxiety. They aren’t witnessing supernatural entities. They’re just feeling themselves, but relocated several feet outside of their bodies by a confused and misinformed brain.

This is a hypothesis, but one that the team can now test in their lab. “We think if you take people into an exhaustive state on a treadmill, their ability to feel a presence would be enhanced,” says Blanke.

Ehrsson adds that although the phantom presences are usually anonymous “shadows”, three of the patients in the study felt that actual family members were behind them. “What are the brain mechanisms that kick in when unknown shadow becomes a real person with a mind of its own?” he asks.

Reference: Blanke, Pozeg, Hara, Heydrich, Serino, Yamamoto, Higuchi, Salomon, Seeck, Landis, Arzy, Herbelin, Bleuler & Rognini. 2014. Neurological and Robot-Controlled Induction of an Apparition, Current Biology http://dx.doi.org/10.1016/j.cub.2014.09.049

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Why Have Female Hurricanes Killed More People Than Male Ones?

Here’s a simple fact with an uncertain explanation: historically, hurricanes with female names have, on average, killed more people than those with male ones.

Kiju Jung from the University of Illinois at Urbana–Champaign made this discovery after analysing archival data about the 94 hurricanes that hit the US between 1950 and 2012. As they write, “changing a severe hurricane’s name from Charley to Eloise could nearly triple its death toll”.


The names certainly don’t reflect a storm’s severity, and they alternate genders from one to the next.

Jung team thinks that the effect he found is due to unfortunate stereotypes that link men with strength and aggression, and women with warmth and passivity. Thanks to these biases, people might take greater precautions to protect themselves from Hurricane Victor, while reacting more apathetically to Hurricane Victoria. “These kinds of implicit biases routinely affect the way actual men and women are judged in society,” says Sharon Shavitt, who helped to design the study. “It appears that these gender biases can have deadly consequences.”

But Jeff Lazo from the National Centre for Atmospheric Research disagrees. He’s a social scientist and economist who has looked into the public communication of hurricane risk, and he thinks the pattern is most likely a statistical fluke, which arose because of the ways in which the team analysed their data.

Let’s look at each of these arguments in turn.

First, Jung’s team asked nine people to rate the name of US hurricane on a scale of 1 (very masculine) to 11 (very feminine). They found that the more feminine names were linked to more damage (normalised to today’s value) and deaths. (They excluded Katrina because that was such a huge outlier.)

To test their hypothesis about gender biases, the team ran six experiments. (For stats junkies, here’s the table showing all the numbers behind the experiments; note that each one involves a fresh group of volunteers.)

When the volunteers saw a list of hurricane names, and nothing more, they guessed that male storms would be more intense than female ones. After reading a more detailed scenario about an incoming hurricane, they predicted that the storm would be riskier and more intense if its name was Alexander rather than Alexandra.

After reading another similar scenario, they were more likely to say that they would evacuate their homes if Hurricane Christopher was hypothetically bearing down upon them, than if Hurricane Christina was doing so. Likewise, if they read a voluntary evacuation order, they were more likely to comply in the face of Hurricanes Danny, Victor or Alexander than Hurricanes Kate, Victoria, or Alexandra respectively

These differences aren’t due to explicit sexism. When the team asked people directly if male or female hurricanes would be more dangerous, the responses were evenly split. “This suggests that the effects in the main experiments are implicit in nature,” says Shavitt. In other words, gender stereotypes influence our thoughts and behaviour, whether or not we buy into them outright.

But Lazo thinks that neither the archival analysis nor the psychological experiments support the team’s conclusions. For a start, they analysed hurricane data from 1950, but hurricanes all had female names at first. They only started getting male names on alternate years in 1979. This matters because hurricanes have also, on average, been getting less deadly over time. “It could be that more people die in female-named hurricanes, simply because more people died in hurricanes on average before they started getting male names,” says Lazo.

Jung’s team tried to address this problem by separately analysing the data for hurricanes before and after 1979. They claim that the findings “directionally replicated those in the full dataset” but that’s a bit of a fudge. The fact is they couldn’t find a significant link between the femininity of a hurricane’s name and the damage it caused for either the pre-1979 set or the post-1979 one (and a “marginally significant interaction” of p=0.073 doesn’t really count). The team argues that splitting the data meant there weren’t enough hurricanes in each subset to provide enough statistical power. But that only means we can’t rule out a connection between gender and damage; we can’t soundly confirm one either.

Other aspects of the team’s analysis didn’t make sense to Lazo. For example, they included indirect deaths in their fatality counts, which includes people who, say, are killed by fallen electrical lines in the clean-up after a storm. “How would gender name influence that sort of fatality?” he asks. He also notes that the damage a hurricane inflicts depends on things like how buildings are constructed, and other actions that we take long before a hurricane is named, or even before it forms.

Then, there are the six experiments. As is common in psychology, the volunteers in the first three were all college students. “There is no reason to think that University of Illinois undergraduate students in hypothetical scenarios would have any relation to real-world decision making to populations in hurricane vulnerable areas,” says Lazo. The participants in the last three were recruited via Amazon Mechanical Turk—an online platform for finding volunteers.  Again, it’s unclear how representative they were of people who live in coastal, hurricane-prone towns.

Finally, Lazo says that there’s a lot of evidence on how people respond to hurricane threats, and how their decisions are influenced by their social situation, vulnerability, culture, prior experience, sources of information, when the hurricane makes land, and so on. “Trying to suggest that a major factor in this is the gender name of the event, with a very small sample of real events, is a very big stretch,” says Lazo. And if the archival analysis isn’t as strong as it originally seemed, then what the team has basically done is to show “that individuals respond to gender”—hardly a big deal. [Update: To clarify, I mean that there’s already a huge amount of evidence that individuals respond to gender, not that the biases themselves are no big deal. Of course, they are.]

All of this matters because Jung’s conclusions, if they’re right, could have implications for how hurricanes are described. “It may make sense to move away from human names, but other labels could also create problems if they are associated with perceptions of mildness or gentleness,” says Shavitt. “The key is to provide information and labels that are relevant to the storm’s severity.”

Lazo says, “If there’s reasonable validity to their findings, it is worth further exploration with real hurricane-vulnerable subjects. That would be the proper conclusion to their study, and absolutely not any specific policy recommendations about changing naming conventions!”

Update: The authors have responded to Lazo’s criticisms in the comments below (see also this PDF). You can also find other critical viewpoints at Mashable, Slate, and indeed, in some of the comments in this piece.

Update 2: Bob O’Hara and GrrlScientist have written another rebuttal at the Guardian, pointing out flaws in the paper’s model. Check it out. I’d also pay attention to comments from Harold Brooks below.

Reference: Jung, Shavitt, Viswanathana & Hilbed. 2014. Female hurricanes are deadlier than male hurricanes. PNAS http://dx.doi.org/10.1073/pnas.1402786111. If the link isn’t working, this is why.

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Why Octopus Arms Don’t Get Tangled

If you cut off an octopus’s arm, the severed limb will still move about for at least an hour. That’s because each arm has its own control system—a network of around 400,000 neurons that can guide its movements without any command from the creature’s brain.

The hundreds of suckers along each arm can also behave independently. If a sucker touches an object, it will change its shape to form a tight seal, and contract its muscles to create a powerful suction. It grabs and sucks, by reflex.

This setup allows the octopus to control its astonishing appendages without overly taxing its brain. Your arm has a small number of joints and can bend in a limited number of ways. But an octopus’s arm can create as many joints as it wants, in any direction, anywhere along its length. It can also extend, contract, and reshape itself. To control such infinitely flexible limbs, it needs to outsource control to the limbs themselves.

But what happens if one arm brushes past another? If the suckers grab objects on reflex, why aren’t octopuses constantly grabbing themselves by mistake?

To find out, octopus arm expert Benny Hochner teamed up with octopus sucker expert Frank Grasso.“Octopus suckers are undervalued in terms of their complexity,” says Grasso. “I’m one of their proponents. They’re really exquisite manipulation devices.”

Together with Nir Nesher and Guy Levy, the duo noticed that the suckers on a freshly amputated arm will never attach to another arm. Sure, they’ll grab skinned parts of an amputated arm or the bare flesh at the point of amputation, but not the arm itself. They’ll grab Petri dishes, but not those that are covered with octopus skin.

Common octopus. Credit: Pseudopanax.
Common octopus. Credit: Pseudopanax.

Octopuses clearly have some kind of sucker-proof coating on their own skin.  The team confirmed this idea by extracting chemicals from the skins of both fishes and octopuses, and applying these cocktails onto Petri dishes. They found that the octopus extract could block a sucker’s grabbing reflex but the fish extract could not.

“We all knew that octopuses are very dependent on chemical sensing but we haven’t done much research on this,” says Jennifer Mather from the University of Lethbridge, who studies octopus behaviour. “This paper will probably kick start it.”

Whatever the mystery chemical, it’s clear that octopuses can override its influence. The team showed that that living animals will occasionally grab amputated arms, even by the skin. Their brains can veto the reflexes of their suckers.

They can even tell if an amputated arm belonged to them or to another octopus. If they sensed another individual’s severed arm, they would often explore it, grab it, and hold it in their beaks in an unusual posture that the team called “spaghetti holding”. (Common octopuses will cannibalise their own kind, so a floating arm is fair game.) But when they sense their own severed limbs, they typically avoided it, and only rarely treated it like food.

“This gives us some idea of how octopuses might generate a sense of self—not by vision, which would be hopeless given their changeable appearance, but by chemical cues,” says Mather.

The octopus’s self-avoiding arms are a great example of embodied cognition—the idea that an animal’s body can influence its behaviour independently of its brain. As Andrew Wilson and Sabrina Golonka explain, “the brain is not the sole resource we have available to us to solve problems. Our bodies… do much of the work required to achieve our goals.”

The octopus… well… embodies this idea. Its brain governs many of its decisions and exerts control upon its arms, but the arms can do their own thing, including getting out of each others’ way. The animal doesn’t need to know the location of each of its arms to avoid embarrassing entanglements. It can let its arms do the work of evading each other.

This concept might be useful for designing robots. A typical robot, like Honda’s ASIMO, relies on top-down programs that control his every action. He can pull off pre-programmed feats like dancing or running, but he trips over even minor obstacles. He’s inflexible and inefficient. By contrast, Boston Dynamics’ Big Dog relies on embodied cognition. His springy legs are designed to react to rough terrain without needing new instructions from his central processor. (Thanks again to Wilson and Golonka for the examples.)

By studying the arms of octopuses, scientists may one day be able to design soft versions of Big Dog, pairing its flexible movements with an equally flexible chassis. Big Octopus, perhaps.

Reference: Nesher, Levy, Grasso & Hochner. 2014. Self-Recognition Mechanism between Skin and Suckers Prevents Octopus Arms from Interfering with Each Other. Current Biology. http://dx.doi.org/10.1016/j.cub.2014.04.024

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On Privilege and Luck, or Why Success Breeds Success

Ask successful people about the secrets of their success, and you’ll probably answers like passion, hard work, skill, focus, and having great ideas. Very few people, if any, would reply with “privilege and luck”. We’re often blind to these factors and they make for less inspiring stories. But time and again, we see that the advantages that give us a head-start and the accidents that ease our path can make or break a career.

In 1968, sociologist Robert Merton noted that in several areas of science, advantage accumulates. Well-known scientists, for example, are more likely to get further recognition than equally productive peers of lesser renown. Merton called this the Matthew effect after a biblical verse that says “For unto every one that hath shall be given, and he shall have abundance: but from him that hath not shall be taken away even that which he hath.”

Merton focused on science but the Matthew effect pervades every area of our society, from bestseller lists to sports leagues. Several experiments have shown that small, random, initial advantages can spiral into huge ones. Success can breed success, and inequality breeds more inequality. Haves have more. Have-nots continue having not.

The latest example comes from Arnout van de Rijt at the State University of New York. His team went to four well-known websites and randomly distributed small bursts of success.

On Kickstarter, where people raise money for specific projects, they picked 100 out of 200 projects and donated a small proportion of their funding goal. On Epinions, where users review products and are paid based on the quality of their appraisals, they gave a “very helpful” rating to some new, unrated reviews. On Wikipedia, where dedicated editors can get status awards to honour their commitment, the team gave awards to a random subset of the most productive editors. And on Change.org, where people call for signatures to support their campaigns, the team gave a dozen signatures to 100 out of 200 early-stage campaigns.

In each case, success came in a different form: money; endorsement; social status; and expressions of support. But these small initial gains always snowballed into significant later ones.

In all four experiments, the early beneficiaries were all significantly more likely to be even more successful. For example, in the Kickstarter study, 70 percent of the projects that got a kickstart went on to attract more funding, while just 39 percent of the unchosen projects did. The lucky projects also attracted more than twice the number of later donations.

Credit: van de Rijt et al, 2014.
Credit: van de Rijt et al, 2014.

These effects lasted for a long time. Two weeks after the experiment, the endorsed reviews on Epinions still had more positive ratings than the others. Three months later, and the lucky Wikipedia editors still had more awards than their equally productive peers.

Van de Rijt’s study also showed that initial bits of success suffer from diminishing returns. They repeated the Kickstarter study but this time, they made either one donation or four, all at the same amounts. They found that 32 percent of the projects with no donors attracted more funding, compared to 74 percent of those with one donor, and 87 percent of those with four. So, a bit of initial success leads to more success, but lots of initial success doesn’t necessarily lead to much more success.

They found the same thing in Epinions. They could boost a reviewer’s eventual standing by giving them one very helpful rating, but giving them four such ratings didn’t do a lot more. A little snowball will careen down the slope into a big one, but a huge snowball won’t create a gigantic one. What matters is that someone kicked off a snowball at all.

Note: the experiments were followed for different times, so the x-axis is normalised. Credit: van de Rijt et al, 2014.
Note: the experiments were followed for different times, so the x-axis is normalised. Credit: van de Rijt et al, 2014.

If the team is right, this means that it would be very hard to exploit the spiralling nature of success through brute force. As they say, “the susceptibility of reward systems to deliberate manipulation may be restricted mostly to interventions favouring those individuals who cannot muster any initial success otherwise”. That might be friends telling each other about an unknown band, or a charity offering jumpstarting loans to underappreciated projects—something to get the ball rolling.

But Duncan Watts, who studies social networks at Microsoft Research, says that these results may not generalise to bigger issues, like careers, societal trends or financial bubbles. “Clearly it’s impractical and unethical to randomly assign people to receive early career advantages, or randomly publish negative news about the housing market, so it’s going to be tricky to get experimental evidence in these systems,” he says. “That’s why the authors have chosen to study the systems they have.  But it’s important to remember that these are all rather simple and special compared to the systems that we really care about.”

Still, the results from van der Rijt’s study are clear: despite their equal merit, some projects or people came to stand above the others, simply because of a small and arbitrarily assigned advantage that they were totally blind to. In other words: privilege and luck.

A skeptic might argue that this effect is a good thing. In this study, advantages were bestowed randomly but in the real world, perhaps they are offered on merit, so that small differences in quality are gradually amplified. But we rarely get the chance to assess merit in a systematic way. No one goes through all of Kickstarter to evaluate every project they see. No one looks at every book in the store before deciding which one to buy.

That is not to say that skill, passion and hard work don’t matter. They clearly do, but studies like this tell us that we can’t assume that success is down to the qualities that emblazon motivational posters, or that people without success somehow lack these qualities.

Reference: Van der Rijt, Kang, Restivo & Patil. 2014. Field experiments of success-breeds-success dynamics. PNAS. http://dx.doi.org/10.1073/pnas.131683611

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Oxytocin: Still Not a Moral Molecule

Whenever the hormone oxytocin makes the news—and it does so regularly—the media can’t help but refer to it as the “love hormone”, “cuddle chemical” or “moral molecule”. Few substances enjoy such a positive public profile. Oxytocin, it is said, is at the core of all our virtues, from trust to empathy to cooperation.

This rose-tinted view is a sham.

As I’ve written before, oxytocin is more of a general social hormone—one that drives us to seek out social situations or that draws our attention to social cues. The results can be positive if we find ourselves in the right situation. Change the context, and oxytocin can reveal a dark side to its influence.

The latest example of this comes from Shaul Shalvi and Carsten de Dreu. They found that people who sniff oxytocin become more dishonest in a simple team game, but only if their lies benefit their group. If they play the game alone, oxytocin doesn’t change their behaviour for better or for worse. As de Dreu says, “This is the best evidence yet that oxytocin is not the ‘moral molecule,’. It doesn’t make people more moral or immoral. It shifts people’s focus from themselves to their group or tribe.”

I’ve written about the study in The Scientist, so head over there for the details. You might also enjoy my piece in Slate about the history of oxytocin hype and why it’s both dumb and dangerous.

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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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Out-Of-Body Experiences Make It Harder To Encode Memories

When Henrik Ehrsson tells me that his latest study is “weird”, I pay attention. This is a man, after all, who once convinced me I was the size of a doll, persuaded me that I had three arms, and ripped me out of my own body before stabbing me in the chest. Guy knows weird.

Ehrsson’s team at the Karolinska Institute in Stockholm specialises in studying our sense of self, by creating simple yet spectacular illusions that subvert our everyday experiences. For example, it seems almost trite to suggest that all of us experience our lives from within our own bodies. But with just a few rods, a virtual reality headset, and a camera, Ehrsson can give people an out-of-body experience or convince them that they’ve swapped bodies with a mannequin or another person.

These illusions tell us that our sense of self isn’t the fixed, stable, hard-wired sensation that it seems. Instead, our brain uses the information from our senses to continuously construct the feeling that we own our own bodies. Feed the senses with the wrong information, and you can make the brain believe all manner of impossible things.

Loretxu Bergouignan joined Ehrsson’s team in 2009. She had been studying memory, and she wanted to know if that brittle sense of self is important for encoding our experience. After all, we take in all the events of our lives from inside our own bodies. As Bergouignan writes, “There is always an “I” that experiences the original event, and an I that re-experiences the event during the act of remembering.” If she put someone through an out-of-body illusion, could they still make new memories? Is that first-person perspective of the world important for storing information about it?

It’s the type of experiment that fits perfectly in Ehrsson’s group, who specialise in answering questions that seem almost too weird to ask in the first place. Still, he recalls, “I thought it was a very high-risk project. But sometimes you need to try riskier projects.”

Bergouignan recruited 32 local students for a “memory experiment” and gave them materials to study beforehand. When the volunteers arrived, Bergouignan fitted them with earphones and a virtual reality headset hooked up to a camera.

Half the time, the camera sat just above their heads and gave them the view that they would normally see (A below). The rest of the time, the volunteers sat facing the camera, so they saw themselves through their headsets (B). The researchers then pushed one rod towards the camera, while synchronously tapping the volunteers on the chest with a second rod. They could see themselves being prodded from afar, but also felt the same prods on their chests. That was enough to induce an out-of-body illusion. (Having experienced this before myself, I can attest to how convincing it is!)

Once the volunteers were under, an eccentric professor—really, an actor—entered and asked them questions about the material they had learned. He was scripted to be eccentric and memorable. He punctuated his questions with random monologues, bizarre provocative statements, and personal asides. “It was like performance theatre where the actors interact with the audience in a real-world environment,” says Ehrsson.

A week later, the volunteers returned to the lab, and Bergouignan asked them about their experiences with the professor. This was the real memory test, and the results were clear. The volunteers who experienced the out-of-body illusions were uniformly worse at recalling the details of the day than those who interacted with the professor from their usual in-body perspectives.

The team repeated the experiment with a slight variation. This time, the camera was at a 30 degree angle, so the volunteers floated out of their bodies but could still see the professor’s face (C). Again, they remembered the events more poorly than their in-body peers.

ExperimentThese are fascinating results. Remember that all the volunteers go through the same events. They’re all in the same place. The professor always sticks to the same semi-structured script. And yet, the angle from which they experienced those events strongly affected their ability to remember them.

The out-of-body illusion wasn’t more distracting; under its influence, the volunteers were just as good at simple mental tasks as they normally were. And it wasn’t just bizarre and off-putting either; after all,  we’re *better* at remembering bizarre events than everyday ones. Instead, the illusion seemed to hamper memories by taking volunteers out of their normal perspectives.

Bergouignan supported this view by placing some of her volunteers in a brain-scanner. She was especially interested in their hippocampus—a seahorse-shaped region near the floor of the brain that acts as a funnel between our experiences and our memories. It binds information from our senses and emotions into cohesive forms that can be stored, and then helps to reactivate that stored information when we want to remember something.

When the in-body volunteers sat in the scanner and recalled their time with the weird professor, their hippocampus behaved in the normal way. It became more active when they first tried to remember the events, and then less active with each subsequent attempt.

But the out-of-body hippocampi did exactly the opposite. “The first time they tried to remember, there was nothing in the hippocampus. It was silent,” says Ehrsson. But the more they tried to remember, the more active the hippocampus became.

This suggests that the volunteers aren’t just remembering a little less when they’re out of their bodies. “Their hippocampus is impaired in a more profound way,” says Ehrsson. He suspects that without the first-person perspective, the hippocampus can’t encode experiences in its usual coordinated way, and volunteers end up with fragmented memories that they struggle to recall. And as they struggle, Ehrsson speculates that they could be creating false memories out of the fragments.

This is a good example of embodied cognition, where basic aspects of our bodies like sensory information can influence “higher” mental skills like our memories. “When we walk around minding our own business, we always have this sense of being located inside our bodies,” says Ehrsson. “You need to have that experience of the world to encode and recall your own memories. This has never been shown before perhaps because it’s so difficult to manipulate.”

That’s a stretch, says Howard Eichenbaum, who studies memories at Boston University. “It is well known that material learned in a particular context is better remembered in the same context than a different one… and the hippocampus plays a key role in using context to guide memory retrieval,” he says. For example, deep-sea divers are worse at remembering what happened to them underwater after they resurface. “The out-of-body effects here may be a special case of context dependent memory.”

Ehrsson acknowledges this, and wants to see if it’s possible to reverse the memory defects by putting volunteers back into the out-of-body illusion.

This could have possible applications. There are many disorders like schizophrenia or borderline disorder where people say that they feel detached from themselves. Many people with post-traumatic stress disorder (PTSD) claim that they remember experiencing traumatic events from outside of their own bodies, and struggle to remember those events clearly. Perhaps those two things are linked. “It’s not that they don’t want to remember what happened for emotional reasons,” says Ehrsson, “but it could be that the memories are damaged because they weren’t located inside themselves,” he says.

“Many such patients report that the subjective element of experience is altered, but this is difficult to verify externally,” says Brian Levine from the Baycrest in Toronto. But Ehrsson’s team have provided scientists with a way of probing these experiences, by manipulating something as inherently subjective as “self-ness”.

“They did not confirm any of their predictions in patients, though,” Levine adds. “There is a big difference between dissociations due to psychological trauma, and the dissociations induced in this experiment. So more work is need to make the connection to clinical syndromes.”

Reference: Bergouignan, Nyberg & Ehrsson. 2013. Out-of-body–induced hippocampal amnesia. PNAS http://dx.doi.org/org/10.1073/pnas.1318801111

More on Ehrsson’s work, see my Nature story: Master of illusion, and the following posts: