Field of Science


The Shambulance: Copying Roger Clemens Won't Help You Lose Holiday Pounds

The Shambulance is an occasional series in which I try to find the truth about bogus or overhyped health products. With me at the wheel of the Shambulance are Steven Swoap and Daniel Lynch.

The injections he'd been receiving in the buttocks during his major-league baseball career, pitcher Roger Clemens explained to a jury this summer, were not steroids. They were perfectly legal and innocent shots of vitamin B12. The jury acquitted him, lifting the weight of a felony perjury charge from his shoulders. You, too, can use B12 to put some spring back into your step—at least, if you believe the companies that market the injections for weight loss, energy, and general well-being. In reality, this is not a performance enhancer.

B12 is a quirky vitamin that you can't get from plants. It's manufactured by bacteria that provide their services to some animals by living in their guts. Humans mainly get B12 from meat, eggs, and dairy. Of course, this means vegan humans have to find the vitamin elsewhere, such as in fortified breakfast cereals or Flintstones chewables. (They might also ingest B12 from soil bacteria on vegetables that haven't been washed well.)

"Healthy individuals have a six-year supply of B12 stored in their liver," says Daniel Lynch, a biochemist at Williams College. So even a temporary shortage in your diet shouldn't harm you. Long-term vegans, though, can become deficient in B12. Some older adults and gastric-bypass patients who can't absorb enough B12 from their food need to get it from an outside source. And patients who suffer from a disorder called (oddly) "pernicious anemia" need B12 supplements.

B12 deficiency causes weakness and fatigue, and an injection of the vitamin reverses those symptoms. This has apparently led some people to conclude that healthy, non-deficient folks will also get stronger and more energetic by taking B12. Why settle for normal functioning when you could be a vitamin-powered superhuman?

"[Weekly] vitamin B12 injections are intended to crank up the metabolism and boost energy levels to increase daily activity and help weight loss even when the body is at rest," says one Chicago weight-loss center.  An "anti-aging" clinic asserts that "B12 injections effective means of boosting the body's metabolism for those looking to lose weight."

You'll start by shedding weight in the wallet region: a 3-month course of shots from that office will relieve you of nearly $500.

It's true that vitamin B12 is involved in metabolism. However, according to the National Institutes of Health, "Vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit."

In other words? "Basically, for any healthy person this is a sham," Lynch says. "Any excess B12 is peed out anyway."

Non-human animals store B12 in the liver, just as humans do. "So you could get the same effect of the injection by munching on liver," says Steven Swoap, a physiologist who's also at Williams College. "This is how they 'cured' vitamin B12 deficiency a hundred years ago."

If you still feel a craving for B12 but don't care for liver sandwiches, you can buy bottles of B12 pills—and they'll run you about five cents a tablet. "It begs the question as to why anyone would stick a needle in themselves when you can buy this stuff as a pill at the local drugstore," Swoap says. Maybe we can find a Hall-of-Fame-nominated baseball player to explain it.

Image: Craig Strachan (Flickr)

Hack Your Wallet: Crisp Bills Are Harder to Spend

Do the strains of Bing Crosby's Christmas standards make you throw cash at salespeople until they give you something you can leave the mall with? Are pricey, between-department-store lattes your early gifts to yourself? Don't panic. Scientists have a way for you to hack your spending this holiday season. 

We consumers, it turns out, are not always rational with our cash. Research in the past has suggested that people are more likely to spend the money they carry if it's in smaller bills. Larger bills seem to have value even in addition to their denomination. A $20 bill, for example, is a little harder to let go of than four $5 bills.

This idea is called the "denomination effect." But it's not the only factor that affects whether we save our cash or spend a little more. Two marketing professors, Fabrizio Di Muro at the University of Winnipeg and Theodore Noseworthy at the University of Guelph, investigated another factor: grubbiness. Do people assign extra value to crisp, clean-seeming bills, regardless of their denomination? And are people eager to get rid of—that is, spend—worn, dirty cash?

Previous research has provided a few reasons why this might be true. One study showed that consumers value an object less after it's been touched by other people. After someone else has had their paws on a product, even if they don't see the touching happening, people aren't willing to pay as much for it. As for currency itself, research has shown that most people think money is dirty—and they're not wrong.

In a series of experiments, Di Muro and Noseworthy tried to sort out consumers' real feelings about their cash. They report in the Journal of Consumer Research that crisp bills are keepers.

Participants in the first experiment tried to solve a series of puzzles and received a $10 bill at the end. Then they were offered the chance to wager their winnings on one final puzzle; if they got it right, they'd receive a $20 bill. Half the subjects started with a worn, crumpled $10 and were shown a crisp new $20 that they could win. Eighty percent of these subjects chose to gamble. The other half of the group had a crisp $10 and were offered a worn $20; less than a quarter of these people chose to gamble. Subjects were much more tempted to gamble their winnings, in other words, when it might have meant upgrading to a nicer-looking bill. (In reality, all the bills in the study were brand-new; the researchers had crumpled some of them until they looked old and worn.)

The researchers also found that the lure of a crisp bill could override the denomination effect. In a second experiment, subjects were given either a $20 bill or four $5 bills to "shop" with (in the lab). When their bills looked old, people with small bills spent more. But subjects with four crisp, new $5 bills spent less than those with a worn $20.

In a third experiment, subjects shopped with a wallet holding an assortment of bills. Most people don't like to break a larger bill if they have the right small bills to pay for what they want. But in this case, people with a larger bill that was old and worn were much more likely to break it unnecessarily. If the larger bill was crisp, almost no one did this.

Based on questionnaires after their experiments, the authors think that two emotions are at play. One is disgust: people think old, crumpled bills are dirty, and like to get rid of them in a hurry. The other is pride: people enjoy owning crisp new bills, and don't want to spend them.

(This sense of pride may be what led to a surprising twist: When the researchers repeated the final experiment but told subjects that they were being videotaped, those people were more likely to break their crisp larger bills. Imagining others' eyes on them apparently made people eager to show off their nice-looking cash.)

Overall, people tended to spend more and get rid of their cash more readily when they had worn, dirty-seeming bills. People with crisp, clean bills spent less and didn't like to break those bills unnecessarily—unless someone else was spying on them.

What does this mean for your wallet? Stocking up on crisp ATM bills, rather than taking cash back at the grocery store, might help you spend less. Keeping large bills instead of small ones will help too.

The government might be able to hack its own wallet, though, by following the opposite advice. The Federal Reserve regularly removes beat-up, grubby cash from circulation and replaces it with new bills. If it replaced worn bills less often, leaving everyone stuck with wallets full of grubby cash, maybe we'd all spend a little more money and give the economy a real holiday boost.

Di Muro, F., & Noseworthy, T. (2012). Money Isn’t Everything, but It Helps If It Doesn’t Look Used: How the Physical Appearance of Money Influences Spending Journal of Consumer Research DOI: 10.1086/668406

Image: 401(K) 2012 (Flickr)

Math Shows Penguins Only Care about Themselves

Don't let the adorable mini-orchestra-conductor look fool you: penguins aren't that nice. When emperor penguins huddle together during Antarctic storms, they act like they're all in it together. But a new mathematical model shows just how the clusters of birds keep warm, accounting for everything from their geometry to the speed of the wind. Concern for one's fellow bird, it turns out, isn't a factor.

Regardless of your motivations, huddling together in a group is a great way to wait out a frigid storm. Instead of burning up their own energy reserves trying to warm their bodies, emperor penguins can rely on the warmth of a bunch of big feathery animals pressed together. There may be ten or hundreds of bodies in the huddle. Inside, the temperature is between 20 and 37.5 degrees Celsius (a cozy 68 to 99.5 degrees Fahrenheit). In the chilliest storms, penguins squeeze as tight as 10 birds every square meter.

Those huddles aren't motionless, though. With a continuous slow shuffling, the penguins rotate through the formation. Birds with their backs exposed to the wind creep away from it, up the sides of the huddle, until they find some protection. Meanwhile, birds that were formerly on the warm interior find themselves on the outside.

Three applied mathematicians at the University of California, Merced, set out to create a computer model of penguin huddling. Aaron Waters, François Blanchette, and Arnold Kim wanted to find out how well the birds' strategy works—and whether any penguins are left out in the cold.

To pack their penguin huddle as tightly as possible, the mathematicians imagined the birds on a grid of hexagons. This is the best way for circles to squeeze into a plane (think of a honeycomb), and scientists in the field have observed that real penguins arrange themselves roughly this way. The researchers also assumed that "penguins in this huddle have uniform size and shape."

Next, they added wind to the model, which flowed around the huddle differently depending on its overall shape. Then they calculated the rate at which each computerized penguin was losing body heat. They sent the coldest penguin shuffling around the outside of the huddle until it found the warmest spot it could stand in, then started over with the new coldest penguin.

The simulated penguins constantly shifted positions within the huddle, just as real penguins do. Over time, the model huddle tended to take on the shape of a flat-sided oval and travel slowly downwind (as penguins on the windward side continuously moved away from it).

When they calculated the flock's heat loss, the authors discovered that their model huddle was very fair: every penguin lost approximately the same amount of body heat. But these model penguins were only programmed to maximize their own warmth, not to consider the warmth of other penguins or the group as a whole. This means that even if penguins are only looking out for themselves, the whole huddle stays warm, as the authors report in PLOS ONE.

Just because emperor penguins can be totally selfish doesn't mean they are, the authors point out. It's still possible that penguins are altruists, organizing their huddle by thinking about the group as a whole. But it's not necessary to explain how they behave in the wild.

There's one flaw in the penguins' strategy: the elliptical shape a huddle tends to take on isn't optimal. A less stretched-out formation would help the whole group stay a little warmer. Maybe the emperor penguins should consult with a mathematician.


ADDENDUM: Francois Blanchette, who was traveling when I first contacted him, says that this research was inspired by (what else?) March of the Penguins. While watching the movie, he noticed that factors in the penguins' environment, such as wind flow and heat transfer, were relevant to his own field of fluid dynamics. "I figured there should be a problem I could address that had to do with penguins," he says. "I was looking to do something different than my usual line of research."

With penguins out of the way, Blanchette and his coauthors are now interested in modeling other groups of living things, such as bacterial colonies. "However, not being biologists," he says, "we are not very familiar with other biological systems where such a model could be useful." If you're a biologist with a clump of organisms you'd like to model, let him know.

Image: Emperor penguins, by Mtpaley (Wikimedia Commons)

Waters, A., Blanchette, F., & Kim, A. (2012). Modeling Huddling Penguins PLoS ONE, 7 (11) DOI: 10.1371/journal.pone.0050277

P.S. If you enjoy reading about math and self-interested animals, you may like my earlier post Geometry Proves Sheep Are Selfish Jerks.

Monitoring from Space Shows Even This Giant Crab Can Navigate Better than You

It was crabnapping for a just cause. But the crustaceans that found themselves suddenly plucked from their burrows, stuffed into opaque sacks, and carried off through the forest couldn't know that. When the scientists freed their captives, they waited to see whether the crabs would find their way home or be stranded forever. They'd be watching—from space.

The best way to find out exactly where and how far an animal travels is to tag it with a GPS tracker. But if you're interested in invertebrates, most of your subjects are too small or squishable to carry around such a device. Enter (scuttling in from stage left) the robber crab, Birgus latro. Also called the coconut crab because of its predilection for cracking open coconuts, the species is the largest arthropod on land. Legs included, it can grow to nearly a meter across.

Robber crabs live on islands in the Indian and Pacific Oceans, tucking themselves into hollow trees and rock crevices during the day to keep their shell-less bodies from drying out. Females make an annual migration to the coast to lay their eggs in the ocean. Less is known, though, about the movements of male crabs. To find out what they're up to—and because the heavier males presumably wouldn't mind the bulky GPS tags so much—Jakob Krieger of the University of Greifswald and other German researchers tagged 55 male robber crabs on Christmas Island.

During the day, the GPS satellites didn't return much data, since the crabs were mostly hidden in their burrows. At night, they began to roam.

The crabs were highly faithful to their homes, usually staying close to the one to three hiding spots they preferred. But during the time the scientists were monitoring them—up to three months—15 of the crabs went on mysterious, long-distance journeys to the coast.

The authors report in PLOS ONE that these journeys were up to 4.2 kilometers long, a distance that might not seem impressive, except that the top speed observed in the study was 150 meters per hour. If you set a shuffling robber crab at one end of a soccer field at the beginning of a game, you just might be able to retrieve it from the opposite end at halftime.

All the journeying crabs traveled along a similar route, sharing a "migratory corridor" toward the ocean. Why do they go on these arduous errands, visiting the coast for 1 to 10 days before returning home? Krieger says he and his coauthors are "convinced that it is most likely a combination of factors."

One possible factor is reproduction; athough they mate inland, male crabs may try to boost their success by pursuing females out to shore. Another is nutrition. Krieger says the crabs may need to drink saltwater to get the calcium and sodium that keep their skin sturdy. They also get the nutrients they need by eating other crabs, such as the red crabs that migrate en masse across Christmas Island every year. Traveling robber crabs may take advantage of this mobile red-crab buffet. (Here's a worthwhile video of red crabs dodging traffic and clinging to cliff faces during their own journeys.)

The fact that male robber crabs traveled at all was news to the scientists. But they also wanted to know how well robber crabs can navigate, and that's where the crabnapping came in. A dozen crabs were bagged, moved a kilometer or so, and re-released to see how they'd manage.

Crabs that were freed somewhere within the migratory corridor, that popular robber crab highway, found their way home with no problem. But those released someplace unfamiliar were lost. The GPS data showed that these crabs used their release points as a new home base from which they took exploratory trips outward, trying to get their bearings. Yet they never found their old homes.

Though robber crabs might navigate using cues such as the position of the sun or moon, the scent of the ocean, or the earth's magnetic field, they seem to especially rely on memorizing a path in one direction and retracing it on the way back. The GPS data showed crabs following identical routes on their way to and from the ocean.

The researchers also crabnapped one of their victims twice, and saw that he followed precisely the same path homeward (along the migratory corridor) both times. This suggests that robber crabs remember the landmarks they find along their routes. Of course, when you're moving at a crab's pace, there's plenty of time to observe the scenery.

Krieger, J., Grandy, R., Drew, M., Erland, S., Stensmyr, M., Harzsch, S., & Hansson, B. (2012). Giant Robber Crabs Monitored from Space: GPS-Based Telemetric Studies on Christmas Island (Indian Ocean) PLoS ONE, 7 (11) DOI: 10.1371/journal.pone.0049809

Image: John Tann (Flickr)

Why You Itch When Others Scratch

Itching is contagious, and not only when one party has the chicken pox. The mere sight of a stranger scratching can be enough to trigger an itch in your own flesh. If you're especially prone to contagious itchiness, psychologists say, it's not because you relate well to other people—you're just neurotic.

The researchers who delved into the science of contagious itching thought it might be similar to another famously spreadable phenomenon: yawning. Previous studies found that a person's likelihood of catching someone else's yawns is linked to empathy. It's easier to trigger contagious yawning in people who are good at understanding others' states of mind.

To explore contagious itching, psychologist Henning Holle at the University of Hull, UK, and his colleagues subjected 51 volunteers to videos of people scratching themselves. Each person watched a series of videos with changing variables: some showed a man scratching himself and others showed a woman; the model scratched 5 different body parts (upper or lower left or right arm, or the middle of the chest); and in control videos the model simply tapped the body part in question.

After each video, subjects rated how itchy they felt. Since the experiment was being filmed, researchers could also see how often their subjects scratched themselves, whether they realized they were doing it or not.

The results showed that itching is highly contagious, the authors report this week in PNAS. People reported feeling itchier after the scratching videos than the tapping videos, and most subjects scratched themselves at some point during the experiment. It's normal to feel itchy when you see someone else scratching. But the degree of itchiness varies from person to person.

To find out what makes someone especially vulnerable, the researchers gave subjects a group of standard personality tests. "We expected to find contagious itching to be associated with empathy," Holle says. A questionnaire that measured empathy, though, turned up no connection.

But the researchers did find a correlation between their subjects' contagious itching and their neuroticism. As defined by psychologists, neuroticism is someone's tendency toward worry and insecurity. Holle and his colleagues measured this and other personality traits using a test called the Big Five personality inventory. (The other four traits in this test are openness, conscientiousness, extraversion, and agreeableness. Worried you're a worrier? You can take a version of the test here.)

Making a study of itching and scratching even less physically comfortable, 18 of the subjects watched the videos while inside an fMRI scanner. They weren't allowed to scratch themselves, since that motion might interfere with the machine. But when they saw scratching videos, the activated areas in their brains matched a previously observed group of regions called the "itch matrix."

Among other areas, this brain network included the premotor cortex (involved in planning and carrying out motions) and the primary somatosensory cortex (headquarters for our sense of touch). Also active was the anterior insula, an area the authors say may be crucial to our feeling of sharing another person's pain.

When asked how itchy this research had made him personally, Holle declined to comment.

Holle, H., Warne, K., Seth, A., Critchley, H., & Ward, J. (2012). Neural basis of contagious itch and why some people are more prone to it Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1216160109

Image: Holle et al.

City Birds Adapt to a New Enemy: Cats

Moving from a rural home into the city brings challenges like figuring out trains, maneuvering couches up staircases, and not being eaten. Birds that move into urban homes have to worry about a different set of predators than their relatives in the countryside do. Although they haven't learned how to avoid hungry truck grilles, urban birds have evolved some new tricks that help them dodge the claws of predatory house cats.

For a bird living in a rural habitat, the main threat is birds of prey. But when that same bird moves to a city, it's much less likely to get snatched from above by a swooping hawk or falcon. Instead, it has to contend with roaming cats. The American Bird Conservancy says that cats (both pets and strays) kill hundreds of millions of birds each year in the United States alone.

To find out whether urbanized birds have evolved in response to their new predators, a pair of researchers captured birds inside and outside of two cities: Brønderslev, Denmark, and Granada, Spain. The researchers are Juan Diego Ibáñez-Álamo, at the University of Granada, and Anders Pape Møller at Paris-Sud University. Using mist nets and traps, they collected 1132 birds.

Each time a bird was caught, a researcher immediately collected and tested it. By simply holding a bird in their hands briefly, the scientists could score all the ways it responded to capture. Did the bird scream out distress calls? Bite? Shed its feathers? When released, did it fly off right away or lie frozen in panic?

The researchers collected members of 15 bird species that lived in both the city and the country. For each of these species, they compared the behaviors of urban and rural birds to determine how the birds had adapted since moving into the city.

Like newly minted Manhattanites learning to keep their doors locked, urban birds have developed new safety habits, the authors report in Animal Behaviour. One such habit is screaming bloody murder. When researchers seized city birds and held them in their hands, the birds were much more likely to make alarm calls and "fear screams" than birds of the same species that lived in the country. Møller and Ibáñez-Álamo think this behavior has evolved because in the city, birds live close to their relatives instead of dispersing widely. Families that alert each other to predators keep their genes alive.

Other habits that may have helped birds escape from raptors when they lived in the country—namely, biting and wriggling around when caught—were less common in city birds. (I'm guessing biting was not as uncommon, however, as the researchers holding the birds would have liked.)

Urban birds also showed off a trick that was less common in their rural relatives: shedding feathers. This trait seems to help deter hungry cats. When finding yourself in the mouth of a house cat is a real danger, being able to shimmy away and leave that cat with a mouthful of feathers will help you survive.

Some of the bird species studied had lived in the city since the late 19th century, while others had only moved in during the 21st century (according to local bird experts who'd monitored their populations). For a couple of the escape behaviors they studied, the researchers were able to see changes increasing over time: birds that had spent a lot of generations in the city had changed more dramatically than recent immigrants had.

This suggests that as birds and other animals continue to reside and reproduce in the city, they'll keep evolving in response to their urban predators. If we give them long enough, maybe they'll even figure out how to escape cars.

Møller, A., & Ibáñez-Álamo, J. (2012). Escape behaviour of birds provides evidence of predation being involved in urbanization Animal Behaviour, 84 (2), 341-348 DOI: 10.1016/j.anbehav.2012.04.030

Image: Jody Sticca (Flickr)

Caffeine Helps Us Recognize Positive Words

Does anyone still say "full of beans"? The phrase is supposed to describe someone who's upbeat and energetic. Maybe we can revive the expression by attaching it specifically to coffee beans, as in, "I just had a double-shot cappuccino and boy, oh boy am I full of beans!"

Caffeine lovers know the feeling of finishing a well-timed cup of coffee or tea: positive, alert, ready to go. (And maybe ready to go to the bathroom.) New research suggests that our brains also process language differently after having caffeine. We're quicker and more accurate at recognizing words—but only if those words have positive connotations.

Lars Kuchinke and Vanessa Lux, researchers at Ruhr University Bochum in Germany, studied the effect of caffeine on a word recognition challenge. To start, they recruited 66 subjects with a range of personal caffeine habits.

Leading up to the experiment, subjects abstained from coffee (and nicotine and alcohol) for at least 12 hours. Thirty minutes before the experiment started, each subject took a pill that contained either sugar or 200 mg of caffeine. That's the equivalent of 2 to 3 standard cups of coffee, or a bit less than 1 tall coffee at Starbucks. Subjects didn't know which pill they'd taken.

Then subjects sat facing a screen with their chins on a chin rest. While they focused on a spot in the center of the screen, words flashed briefly on one side or the other. Half the time, these were emotionally positive, negative, or neutral German words. The other half the time, they were nonsense words that looked similar to German ones. Subjects pressed a button indicating whether the word they'd just seen was real or not.

On the whole, people performed better on this task when the words flashed in front of their right eyes. This was expected, based on previous experiments and the fact that the right eye connects to the left hemisphere, the brain's language headquarters. What was more interesting was that on left-hemisphere trials, people who had taken a caffeine pill were significantly better at recognizing positive words than neutral or negative ones.

The researchers think the effect is down to dopamine. In addition to waking you up and making you quicker and more accurate at cognitive tasks, caffeine increases the activity of dopamine, a signaling molecule in the brain. (This may also be why caffeine drinkers say it improves their mood.)

Previous studies found that the brain is a little better at recognizing positive words (and happy faces) in general. Adding caffeine—and therefore dopamine—exaggerated this effect. Kuchinke and Lux think this is because dopamine interacts with the brain's language centers to make us quicker at processing positive words. They haven't yet studied how caffeine affects our understanding of outdated idioms.

Kuchinke, L., & Lux, V. (2012). Caffeine Improves Left Hemisphere Processing of Positive Words PLoS ONE, 7 (11) DOI: 10.1371/journal.pone.0048487

Image: Dan Barbus (Flickr)

Belly Button Safari: Who's Living in There?

"We are covered in an ecological wonderland," declares Rob Dunn, a man with a strange idea of a wonderland. In the wild bacterial jungle that is our skin, Dunn has been studying an especially dark cave: the belly button. He's found out which microorganisms are the big game, which are the rare birds, and which ones may take up residence in your navel if you stop bathing.

Dunn is a biologist at North Carolina State University who studies the tiny life forms that share our personal space, from insects in our yards and houses to microbes on our bodies. The organisms we live with can affect our health, for better or worse. Yet researchers are only beginning to explore the various ecosystems we carry on ourselves. From our intestines to our faces to the bottoms of our feet, each of us holds a planet's worth of different habitats.

Out of all these bacterial habitats, the belly button is especially convenient to study. Everyone has one. Its shape and size don't change dramatically from person to person (among innies, anyway). And it's hard to scrub clean, making it a relatively undisturbed environment on the body. A national park, if you will.

The belly button also has crowd appeal, which is important for Dunn's citizen-science approach. He's interested in projects that involve unsqueamish members of the public. For his belly button research, Dunn recruited crowds at two 2011 events: One was Darwin Day at the Museum of Natural Sciences in Raleigh, North Carolina, and the other was the annual Science Online conference in Raleigh.

In total, 60 volunteers had their navels swabbed. Researchers extracted the bacterial DNA from each sample, sequenced it, and searched it for matches to particular species.

What the team found was diversity, and lots of it, as they report today in PLOS ONE. With a median of 67 different bacterial species per person, Dunn says the navel is at least as diverse as the other skin areas studied so far. That diversity varied widely; some people housed more than 3 times as many species in their belly buttons as others.

Out of the thousands of bacterial species the researchers found overall, the vast majority showed up in only a few people, or in just one person. Even though this habitat looks similar from one person to the next, we all have very different collections of rare critters running around in the undergrowth. No one bacterial species appeared in every belly button.

But there are common belly button denizens, too. On our umbilical safari, these are big obvious trees and loud monkeys that show up in most people's jungles. Eight species of bacteria were present in more than 70% of subjects. And wherever these species show up, they do so in large numbers. If you could dump the bacteria from everyone's belly buttons into one pile, members of the 8 king-of-the-jungle species would make up nearly half the heap.

Extending this group to the 23 most common bacterial species, the researchers looked at how the group's DNA compared to rarer bacteria. They found that the ruling bacteria were more closely related to each other than randomly selected groups of bacteria were—sort of a royal family. This suggests that the most common belly button bacteria share evolved traits that help them thrive in this environment.

The most surprising thing about the belly button bacteria, Dunn says, is their ultimate predictability. Even though thousands of species turned up in his study, he now knows which ones are most likely to live in someone's navel. "I expected that the common species would be far more random," he says. "But the truth was otherwise." There are only a few bacteria ruling the belly button jungle, and a diverse throng of others that make up their subjects. Dunn thinks we might be able to study what goes on in our skin's ecosystem by focusing on these few common bacteria.

Dunn hopes that eventually he'll be able to predict the specific bacteria living in someone's belly button based on their age, gender, habits, and history. "But I'll admit we are having an interesting struggle," he says. The research shows that people can be sorted into two or three "bacteriotypes," like blood types, based on the clusters of bacteria that inhabit their navels. But as to why a person is one type or another? "So far we can't explain what causes those differences," Dunn says. "It is a real mystery."

He's getting a little help in this area from one Science Online participant who claimed not to have showered or bathed in "several years." This subject's belly button swab turned up two species of archaea—single-celled organisms, entirely separate from bacteria, that often live in extreme environments. Until now, no one had found archaea on human skin.

This social non-conformer might represent the kinds of bacteria that our ancestors carried around. "Historically, no one washed very often," Dunn says. "This colleague of yours may be far more representative of how our bodies were for thousands, or even millions, of years than are most folks."

He adds, "That isn't saying I'm encouraging everyone to abandon washing."

Dunn suspects that belly button depth, too, might influence what species live there. But he's had a hard time studying this. "No one really wants to answer a question about the depth of their innie, no matter how anonymous we make the process," he says. However, his group's next study will look at a larger group of people, including outies.

Future safaris into our bodies' ecosystems might help scientists understand skin allergies and other health issues. Although belly button sampling is over for now, Dunn encourages people who want to get involved to join the mailing list at He's currently looking at camel crickets in basements, ants in yards, and bacteria in bedrooms and kitchens.

"Armpits," Dunn adds—or perhaps threatens—"are also on the horizon."

Jiri Hulcr, Andrew M. Latimer, Jessica B. Henley, Nina R. Rountree, Noah Fierer, Andrea Lucky, Margaret D. Lowman, & Robert R. Dunn (2012). A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, but Predictable PLOS ONE : 10.1371/journal.pone.0047712

Images: Copyright Belly Button Biodiversity.

Math-Phobes Experience Arithmetic like Bodily Pain

If subtraction makes you sweat, division gives you diarrhea, and the Pythagorean theorem inspires panic attacks, you might be afflicted with math anxiety. Others may not always be sympathetic to your fear of tipping in restaurants without your cell phone. Brain scans, though, show that people like you suffer from more than just nerves. In people who are highly anxious about math, the threat of doing arithmetic activates the same brain areas as a punch in the stomach.

Researchers at the University of Chicago's Human Performance Lab study how humans think and what makes us succeed—or not—under pressure. Anxiety has been found to heighten our awareness of our bodies and make us more sensitive to pain. So Ian Lyons and Sian Bielock wondered whether feelings of anxiety might have a direct connection to pain centers in the brain.

For their anxious guinea pigs, Lyons and Bielock used humans with "high math anxiety." They measured math anxiety using a survey in which subjects rated how anxious they'd feel in various scenarios, including "walking to math class" and "being given a set of addition problems to solve on paper." From their potential subjects, the authors selected 14 people who scored especially high on this test and 14 others who scored especially low. Subjects were also tested for general anxiety (to make sure their math fears weren't part of an allover nervous disposition) and working memory (to ensure that their problem-solving capacity was normal).

Then all the subjects solved a series of math and word questions while inside an fMRI scanner. For the math questions, subjects saw equations like (3 * 5) – 4 = 11 and had to decide whether they were true or false. Some of the equations involved larger numbers to make them harder. For the word questions, subjects saw sets of letters such as yrestym and had to decide whether they spelled a real English word backward.

Subjects with high math anxiety struggled with the harder arithmetic problems more than subjects with low math anxiety did. And in the high-math-anxiety subjects, math problems lit up brain regions involved in sensing pain. Specifically, pain in the gut.

These brain areas, the dorso-posterior insula and mid-cingulate cortex, "are active during the experience of visceral pain—for example, a stomachache or a gut punch," says Ian Lyons. "These areas are also involved in detection of threat to the body." So while people with a lot of math anxiety may not feel bodily pain when facing a math test, their brains seem to interpret each arithmetic problem like a physical threat.

Earlier research found that those same brain areas were activated when people experienced social rejection, Lyons says. Our brains apparently view getting ditched by our friends, or (for some of us) solving for x, like being kicked in the liver.

But what was most surprising about the results, Lyons says, was the timing of that kick-in-the-gut reaction. It happened not when subjects were actually facing those dreaded arithmetic problems, but a few seconds before.

Subjects saw a yellow circle or a blue square, indicating whether a math or word question was coming their way. When they saw the shape and started anticipating a math problem, high-anxiety subjects' pain centers lit up. But once they actually started working on the problem, those brain centers retreated again.

"This underscores the fact that anxiety is very much about the psychological interpretation of an event or phenomenon, and not so much about the event itself," Lyons says. He and Bielock write that once people focus on solving an equation or other problem, they may not have the mental resources left over to keep feeling anxious. To stop the pain of anticipation, serious math-phobes—and perhaps the rest of us too—should just do it already.

Lyons, I., & Beilock, S. (2012). When Math Hurts: Math Anxiety Predicts Pain Network Activation in Anticipation of Doing Math PLoS ONE, 7 (10) DOI: 10.1371/journal.pone.0048076

Image: Shurik_13 (Flickr)