You Might Have Outgrown Synesthesia as a Kid

Feeling smug because your normal brain doesn't insist on coloring all its 2's blue and M's purple? Not so fast: you might have been a child synesthete. Some elementary schoolers have associations between colors and letters or numbers that fade as they age. Others' associations expand to take over the whole alphabet, leading them toward a rainbow-hued adult life.

Studying kids with synesthesia is tricky, because first you have to find them—and at a young age, kids don't know the word, or that their perceptions aren't standard. University of Edinburgh psychologist Julia Simner screened 615 kids for synesthesia back in 2009. Starting with six- and seven-year-olds, Simner and her coauthors sat the kids in front of a computer screen and told them to play a game: they'd see a letter or number next to a set of colors, as above, and should choose the "best" color for each one.

After the computer ran through every letter and numeral in random order, it paused for several seconds, then did the entire test a second time. Forty-seven of the kids were significantly consistent in their choices between the two tests—which meant either that they were synesthetic, or that they had a good memory for colors they'd picked at random. The moment of truth came a year later, when those 47 kids sat down and took the test again. People with synesthesia should be consistent not only over a few minutes, but over years. That's because it's not really a test of memory for them; color is simply a quality that a letter or number has, like being even or a consonant. (For rarer types of synesthesia, people might experience colors with sounds, or tastes with words.)

In 2009, Simner found eight girls and boys who passed her tests. For a new study published in Frontiers in Human Neuroscience, Simner and coauthor Angela Bain returned to these patient elementary schoolers—now 10 or 11 years old—and did the test a third time.

They wondered whether any kids' synesthesia would have faded over the intervening years. Anecdotally, some adults say they remember having synesthesia as a child and growing out of it. The researchers started with not just their eight synesthetes, but 39 of the kids who had been classified as near misses in the first go-around—they had been consistent over 10 seconds, perhaps, but not over a year, or their performance had been just shy of statistically significant. Another 40 average kids served as controls.

This time, six kids passed the test. They were consistent both within two trials and compared to their original tests four years earlier. On testing day, these synesthetes made consistent color choices for about 26 out of the 36 letters and numerals they saw. Non-synesthetes were consistent for only 6 or 7.

Five of the children were from the original batch of synesthetes, and the sixth had been a near miss originally. The other three original synesthetes were no longer significantly outperforming their peers in choosing consistent colors. This may be evidence of "synesthetic demise," the authors write.

Young synesthetes losing their colors over time would fit with a popular theory about synesthesia, which says that it comes from an overly connected brain. "All very young children have hyper-connected brains," Simner says; the neurons branch out indiscriminately between different areas. As we grow, the unneeded connections are pruned away, a process that continues throughout childhood. "It may be that synesthetes escape the pruning, so to speak," Simner says. All kids might start out with some degree of synesthesia, which fades away with normal development.

It's also possible, Simner says, that the "near-miss" kids actually had synesthesia that was developing more slowly than their peers'. She found that synesthetes add more and more colored characters to their rosters as they age. When synesthetes were six or seven years old, they had consistent colors for only about a third of letters and numbers. In another year that number had risen to almost half, and at age 10 or 11 over 70% of letters and numbers had fixed colors. Adult synesthetes have consistent colors for 80 to 100% of letters and numbers.

So for people who don't lose their synesthesia as they age, it becomes steadily more consistent. Now that Simner's subjects are 14 and 15 years old, she says, "we very much hope" to test them again. The teenagers may be happy to learn that at least one thing about their lives is becoming less chaotic.

Image: Simner & Bain 2013.

Julia Simner, & Angela E. Bain (2013). A longitudinal study of grapheme-color synesthesia in childhood: 6/7 years to 10/11 years. Frontiers in Human Neuroscience DOI: 10.3389/fnhum.2013.00603

The Elderly Make Even Worse Decisions Than Teens

The wisdom of aging may not apply to economic decisions. In a study of choices make about money, the oldest people performed the worst—even beating out the usual bad-decision champions, adolescents.

Agnieszka Tymula, a decision scientist at the University of Sydney in Australia, studies economic decision making in humans (and sometimes monkeys). With colleagues at Yale and New York University, she gathered 135 total subjects in four different age groups: teens (12-17), young adults (21-25), "midlife" adults (30-50), and older adults (65-90). All the elderly subjects were screened for dementia to make sure they had healthily aging brains.

At the start of the experiment, researchers gave the subjects $125 in cash. It was theirs to lose—or to more than double, depending on the choices they made. Then subjects made a series of quick decisions. For example, would you rather take a guaranteed loss of $5, or play a "lottery" where you're equally likely to lose $8 or $0? What about a guaranteed gain of $5, versus a lottery an unknown chance of winning $20 that's somewhere between 25 and 75 percent?

In these kinds of experiments, it's normal for people to avoid risk when making money—to accept a guaranteed $5, say, even if a 50-percent shot at winning $12 is a better choice on average. With losses, people act the opposite way; we'd rather enter the lottery than take a guaranteed loss.

There are other decisions that are just plain wrong, though. For example, if given a choice between a guaranteed gain of $5 and a lottery with a chance of winning $5, everyone should take the sure money. But people didn't always do this in the experiment. The two middle age groups made these wrong choices around 5 percent of the time. Teens, 10 percent. And older adults, when given a choice with a clear right and wrong answer, chose incorrectly almost 25 percent of the time.

Over the course of the experiment's 320 decisions, the oldest adults were also the most likely to behave inconsistently, choosing the opposite of what they'd done earlier when facing the exact same choice. (Teens, again, were in second place.)

At the end of the experiment, the researchers gave subjects actual cash (or took it away) based on a subset of the choices they'd made. If every decision had been for real money, the oldest adults would have walked away with a walloping 39 percent less cash than young adults. Middle-aged adults did roughly as well as young adults, and teens did a bit worse—though not nearly as badly as the elderly.

Agnieszka Tymula says the choices in her experiment, which was sponsored by a grant from the National Institute on Aging, are simplified versions of real choices we make all the time. "Most important real life decisions are taken under conditions of uncertainty," she says. When we invest in the stock market or choose a health insurance plan, we have to weigh unknown risks and payoffs. And we may have a harder time making those decisions as we age. The authors write, "Elders borrow at higher interest rates, use credit balance transfers suboptimally, misestimate property value, and pay more fees to financial institutions."

In future studies, Tymula wants to try to pin down what biological changes lead an aging brain to worse choices. "Ideally, we would like to follow a very large sample of people throughout their whole lives," she says, "to precisely identify when changes in decision-making occur and identify risk factors." This might help researchers design treatments that will dial back the brain to a younger mode of decision-making—though not, of course, all the way back to the teenage years.


Image: by Artis Rams (via Flickr)

Agnieszka Tymula, Lior A. Rosenberg Belmaker, Lital Ruderman, Paul W. Glimcher, & Ifat Levy (2013). Like cognitive function, decision making across the life span shows profound age-related changes. PNAS DOI: 10.1073/pnas.1309909110

Uncoordinated Eyeballs Keep Kids from Reading like Adults

Before new readers can move from Dr. Seuss to Doctor Zhivago, it's not only their vocabulary and appreciation of the Russian aesthetic that have to mature. Young eyes just don't move across words as easily as older eyes do. Like Thing One and Thing Two, the eyes bounce around independently and cause disorder.

The difference is in saccades, the little horizontal or vertical hops that ratchet our eyes through sentences. French researchers Magali Seassau of e(ye)BRAIN and Maria-Pia Bucci of Hôpital Robert Debré have been studying how this system develops in kids, including those with dyslexia.

For their latest study, the authors gathered 69 kids ages 6 to 15, as well as 10 adults. While using an eye-tracking device, the subjects silently read a paragraph of text from an age-targeted book. (Experimenters asked questions afterward to make sure the kids had actually read it.) In a separate task, subjects were given the same paragraph—except that all the vowels had been replaced by consonants. They had to skim the text and count the number of r's.

Seassau and Bucci saw evidence of several ways in which a person's reading machinery gets more efficient with age. As subjects got older, they made fewer saccades: their eyes took bigger, smoother jumps forward through the text, and fewer backward jumps. They also paused for less time in between leaps.

These findings fit with what the researchers had seen in earlier studies of reading. "The process becomes automatic" as kids age, Seassau says. "Reading gets to be faster, better and easier."

Younger kids are also worse than older kids or adults at keeping their two eyes coordinated with each other. This means saccades happen unevenly. In kids, "Eyes aren't coordinated when they jump forward on the letter or on the word," Seassau explains. Like competitors in a three-legged race, the eyes have to learn how to match their stride if they want to reach the finish line quickly.

Whether subjects were reading words or searching nonsense text for a certain letter, they got faster with age. Yet there were revealing differences in how their eyes and brains handled the two tasks.

Adults were faster and more accurate at reading than at searching. In the search task, their eyes worked inefficiently, making more saccades. The same thing was true of kids 10 and older. But kids ages 6 to 9 made the same number of jumps whether they were reading real words or hunting for letters in the nonsense paragraph. Younger kids read more like it's a scavenger hunt; older kids and adults read like they're running on a track. The results are in PLOS ONE.

None of the kids or adults in this study had unusual reading difficulties, but Seassau and Bucci are planning to expand their current research to kids with dyslexia in different countries. Earlier eye-tracking studies have hinted that dyslexic kids move their eyes through text in an immature, uncoordinated way. Learning more about how they read may help get everyone's eyes acting their age.


Images: Peter Rohleder (via Flickr); Seassau and Bucci.

Magali Seassau, & Maria-Pia Bucci (2013). Reading and Visual Search: A Developmental Study in Normal Children PLOS ONE DOI: 10.1371/journal.pone.0070261

Swapping Bodies with a Child Makes Everything Seem Bigger

Remember revisiting your preschool or kindergarten classroom once you were older, and realizing all those tables and sinks that are normal-sized in your memory were actually miniature? And that the giant hill you used to struggle up is more of a mound? Adults can regain that feeling of living in an oversize world just by putting on a virtual-reality headset. (Large kid who used to budge you in line for the slide not included.)

This is the latest spinoff of the rubber-hand illusion, a phenomenon in which watching a rubber hand being stroked with a paintbrush, while you feel a matching sensation on your own hand, creates an eerie sensation that the rubber hand is your own. Another recent study found that kids experience the illusion more strongly than adults. Aside from being a neat party trick, the research may have implications for amputees who experience phantom limbs.

The illusion's newest incarnation, by Mel Slater at the University of Barcelona and others, didn't use any physical contact. Instead, subjects wore virtual-reality goggles that let them see through the eyes of a virtual body. The avatar's movements were matched to their own with motion tracking, and subjects could watch their virtual bodies in a mirror while they moved and stretched.

Although the virtual body matched a subject's movements, it didn't match his or her size. The avatars were all miniature people--either a child about four years old, or an adult scaled down to the same height.

With either kind of small body, subjects reported that they felt an illusion that the avatar's body was their own. Researchers quantified this by having subjects look at different-sized objects in the virtual world and hold out their hands to indicate how wide the objects were. (For this part of the experiment, they couldn't see their virtual hands.)

Size perception is always tied to the size of your own body, Slater says, so all subjects overestimated the size of the objects they saw. The same thing happened in an earlier rubber-hand study that had subjects inhabiting both tiny and giant bodies.

But with a child's body, the effect was significantly greater, the authors report in PNAS. People virtually inhabiting a four-year-old's body perceived objects as even larger than people inhabiting a small adult body did.

The authors think this may be because the experiment triggers specific, first-person memories of being in a child's body. Living in a miniature adult body, of course, is a less common experience. This is a "possible new discovery," Slater says—"that the brain codes for body type, not just for size."

Slater has experienced the illusion himself. "It is very powerful and strange to see yourself in a mirror as a small child," he says. Maybe stranger, even, than those tiny sinks.


Image: Slater et al. (from supplemental movie)

Domna Banakou, Raphaela Groten, & Mel Slater (2013). Illusory ownership of a virtual child body causes overestimation of object sizes and implicit attitude changes PNAS DOI: 10.1073/pnas.1306779110

Happy Blogday! Help Me Rename This Site

Inkfish is three years old today!

One great thing about blogs that doesn't apply to real three-year-olds is that you can change their name and appearance at will. I'm getting tired of "Inkfish"—too mysterious, too many creepy arms. Too much guilt about mistakenly calling octopus arms "tentacles" on occasion.

So I'd like to give the blog a new name and a new look. Below are several directions I'm considering. I hope that you, readers, will weigh in.

**********

Welcome! You Probably Got Here by Googling Your Juice Cleanse Symptoms
Tagline: Or Searching for Ionic Foot Detox Reviews
Alternate tagline: I Write About Other Stuff Too. Check It Out When You're Less Hazy
Banner art: a weeping woman with her feet in a small tub of brown water. Foregrounded, a glass of kale juice with a party umbrella.
Inspiration: juice cleanses, foot detox, everything else.

Why I Couldn't Hang Out Last Night
Banner art: a blogger on a couch in a dark room, gently lit by the glow of the laptop screen.
Inspiration: purely fictional.

Every Study About Penguins
Banner art: penguins.
Alternate art: not penguins. Irony could increase my readership among hipsters.
Inspiration: penguins, penguins, penguins, penguins, penguins.

The Loom
Banner art: portrait of Carl Zimmer.
Inspiration: trying to lure Bing users who are searching for Carl Zimmer's blog, The Loom.
Potential complication: lawsuit.

Animals with Things on Their Heads
Banner art would be a rotating selection of photos: crabs wearing GPS devices, pigeons carrying cameras, penguins with earmuffs, and this seal.

Inspiration: animal stalking, pigeons.

Girl That Poops Flowers
Alternate title: Most Inconvenient Moments to Have Narcolepsy
Banner art: a mouse that's quiet—too quiet.
Inspiration: unusual internet searches addressed at the help desk.

Adventures in Bodily Fluids: An Ongoing Quest to Make My Grandmother Admit She Doesn't Love Everything I Write
Banner art: the empty vanilla ice cream bowl I considered using to illustrate a story about sperm-eating flies.
Inspiration: see above.

**********

Please leave your votes in the comments (or just say hello). Thanks for your help, and thanks as always for reading!

Aging Makes People Colon-Close-Parenthesis

Getting older is not a recipe for crotchetiness. Although those two cranky Muppets will always be up in their balcony, Americans in general don't become less happy with age. If anything, they get happier.

The trajectory of people's happiness over a lifetime is tricky to study, because in a given year you're capturing not only your subject's age but also the current events. You need to follow a large group of people over many years, and you need them to be all different ages when the study starts.

Angelina Sutin and her colleagues at the National Institute of Aging in Maryland had just such a dataset to work with. Called the Baltimore Longitudinal Study of Aging (BLSA), this project has been running for more than five decades and has gathered data on people born everywhere between 1885 and 1980. These subjects have answered questions about their happiness on many occasions—some as many as 19 times—throughout their lives.

Want to find your own happiness score? Answer the following questions on a scale from 0 to 3, where 0 is "rarely or never" and 3 is "most or all of the time." In the past week of your life, how frequent were these feelings?

     I enjoyed life

     I felt I was just as good as other people

     I felt hopeful about the future

     I was happy

Summing the four numbers will give you your well-being score. If you were in the BLSA, that score would be your data point for today.

When the researchers put all 2,267 subjects together and looked at how their happiness changed with age, they got a decidedly downward slope. A frowny face, if you will.

age = : ( 

It looked like aging made people less happy. But then the researchers tried a different tactic. Instead of lumping all their subjects together, they grouped them by when they were born. That frown turned upside down:

age = : \

Within each birth year, the results now looked like a somewhat more optimistic "meh?" face. Every group's well-being slightly (but significantly) improved with age.

The first set of results had sloped downward because people who were born earlier reached lower endpoints of well-being. In the graph, you can see that someone born in 1905 or 1925 is likely to reach a 9 or a 10 later in life; someone born in the 1960s might make it nearly to 12 (a perfect score).

Sutin thinks this could have to do with the biggest national frowny-face of all: the Great Depression. People who lived through this time, she writes, may have felt lasting psychological effects. Although their well-being still improved as they aged, the cloud of the Depression may have lingered.

(Sutin notes also that younger and older adults, according to previous studies, treat this set of well-being questions and the 0-to-3 scale similarly. This suggests the results aren't just happiness inflation—say, younger people reporting a 12 for the same feelings that older people would rate a 10.)

Aside from increasing economic prosperity in the United States, there are plenty of other reasons people may have felt happier in more recent decades. Sutin cites increased life expectancy, decreased infant mortality, better nutrition, less disease, and more women in the workplace as possible factors. The twentieth century also saw faster travel, the invention of the Internet, and the eradication in America of both the polio virus and gelatin-based entrées. There's a lot to be happy about.

Now that Sutin has found that the average American seems to have an upward trajectory of well-being, she's interested in people's individual paths: what makes one person's happiness increase more or less (or decrease) over time?

In this study, subjects who were white had higher well-being scores on average, as did those with more education. Sutin hopes to pick apart the social, economic, and health factors that affect how happiness changes with age. When everyone can feel as :) as they want, we'll really be living in the future.

Sutin, A., Terracciano, A., Milaneschi, Y., An, Y., Ferrucci, L., & Zonderman, A. (2013). The Effect of Birth Cohort on Well-Being: The Legacy of Economic Hard Times Psychological Science DOI: 10.1177/0956797612459658

Image: a 102-year-old woman, by Uppy Chatterjee (Flickr)

Mom's Genes Make Males Die Sooner

Men who make it to adulthood without succumbing to the male habit of dying in accidents shouldn't congratulate themselves too soon: their life expectancy still doesn't match a woman's. In industrialized countries, women at every age out-survive men. And it's not just humans. Males that die before females have been observed throughout the animal kingdom. It's even true of the lowly fruit fly, and it looks like harmful mutations in mothers' genes are to blame.

This idea, which has been put forward before, is called the Mother's Curse. It has to do with a little loop of DNA that's passed down in humans—and in most other animals—exclusively through the mother. This DNA hides inside the mitochondria, which are the cell's batteries, and doesn't get packaged up with the rest of the genetic material when sperm are made. Those tiny sperm will rendezvous (if they're lucky, of course) with an egg that supplies all its own mitochondria, along with their DNA.

The Mother's Curse theory says that since fathers don't get any say in the makeup of mitochondrial DNA, it could carry mutations that harm men without being weeded out by natural selection. These anti-male mutations might be the reason for males' shorter lifespans.

Researchers led by Florencia Camus at Monash University in Australia examined this question in fruit flies, an animal whose genes are well understood and easily fooled with. By crossbreeding different fly types, they created 13 lines of fruit flies that were identical except for their mitochondrial DNA. They watched these flies for differences in male and female lifespan. Then they sequenced the mitochondrial DNA itself to see what was driving those differences.

In a study published in Current Biology, the team found that males died sooner across all the fly types. They also saw wide variation in male longevity, while female lifespans were more consistent. Females in most of the lines lived for around 60 days; males were variable but never lived much longer than 50 days. Since their mitochondrial DNA was the only thing that differed between the flies, something in that DNA must have been responsible.

Looking at the actual letter-by-letter differences in the mitochondrial DNA, the researchers found that fly types that were farther from each other genetically also differed more in longevity. In other words, more mutations in the mitochondrial DNA led to more variability in lifespan. Together, these findings support the idea that mitochondrial mutations cause males to die early—in fruit flies, anyway.

Mutations that somehow harm males, but not females, are free to pile up in the DNA of mitochondria. Since females pass down this DNA on their own, evolution is essentially blind to its effect on males. It remains to be seen whether the same mechanism is at work in animals that aren't fruit flies, including humans. If so, men will be able to blame their mothers for their shorter life expectancies. They might want to find a more positive way, though, to fill their abbreviated time on Earth.



M. Florencia Camus, David J. Clancy, & Damian K. Dowling (2012). Mitochondria, Maternal Inheritance, and Male Aging. Current Biology DOI: 10.1016/j.cub.2012.07.018


Image: someecards.com

Non-Aging Plant Gets Better Every Century

Clinging to rock piles high in the Pyrenees, the plant Borderea pyrenaica has a modest lifestyle: It grows a new shoot every summer, flowers and fruits, then sheds its aboveground growth to survive the winter as a tuber. What's remarkable is how long this life lasts for. Individual plants have been known to live 300 years or more. Scientists headed up into the mountains to find out whether these plants, in all their years of living, ever actually get old.

"Senescence" is what we usually call aging--getting weaker and closer to death as we get on in years. To us humans, it seems like a fact of life. But some other animals are thought to be "negligibly senescent." Certain fish, turtles, and other sea creatures seem to be perfectly healthy and fertile at 100 or 200 years old; they're no more likely to die at that age than at any other. Some plants, and especially some trees, may have nearly unlimited lifespans.

Scientists--not to mention cosmetics companies--would love to know exactly why humans are stuck with senescence while organisms like the bristlecone pine just get more fabulous with age. Unfortunately, it's difficult for those of us with limited lifespans to study those without. To squeeze some secrets out of Borderea pyrenaica, scientists from Spain and Sweden studied two populations of the plant over the course of five years.

Because Borderea pyrenaica is left with a scar on its tuber when each year's growth dies back, researchers could count the scars to calculate an individual tuber's age. Each year, they counted and measured the leaves on each plant. They also counted the plants' flowers, fruits and seeds. Since the plants come in male and female versions, the researchers would be able to compare aging in both--would the metabolic effort of making fruits and seeds take a toll on female plants' lifespans? At the end of the study, the researchers dug up all the tubers, dried them and weighed them. (Aesop says: Don't be jealous of negligibly senescent organisms. If old age doesn't kill you, science will!)

The researchers were able to calculate the age of almost 750 plants that were up to 260 years old. They found that tubers grew in size each year, reaching their maximum size after 50 or 100 years (depending on the population). As the tubers grew, the shoots that they put out each year got bigger too. After they reached about 60 years old, the plants didn't seem any more likely to die with the passing years. If anything, survivorship seemed to increase in old age. There was no difference between male and female plants.

As they got bigger, both types of plants put out more flowers, giving them greater potential to contribute to the next generation. This meant that the plants' "reproductive value"--an individual's expected fertility from its current age onward--actually increased over their entire lifespan.

It seems unlikely that we'll one day tap into some biological secret that enables us to live forever. But further research into the plants and animals that don't deteriorate with age might help us solve the mysteries of our own mortality. We may not ever become ageless, but we could learn to age with some of the grace of a lobster, or a mountain tuber.


Garcia, M., Dahlgren, J., & Ehrlén, J. (2011). No evidence of senescence in a 300-year-old mountain herb Journal of Ecology DOI: 10.1111/j.1365-2745.2011.01871.x

Science's Biggest Cancer Questions

The National Cancer Institute wants to give out $17.5 million to scientists studying the biggest unanswered questions about cancer. To figure out what those unsolved mysteries are, NCI director Harold Varmus pooled ideas from researchers, eventually developing a master list of 24 "provocative questions." The NCI is now inviting researchers to apply for some of that grant money--but scientists are only eligible for part of the pot if they promise to specifically address one of the 24 questions.

Some of these unanswered questions (or PQs, as the Cancer Institute has catchily dubbed them) are old, neglected mysteries. Others are based on newer observations. And some are questions that we haven't had the technology to address in the past, but that seem more attainable today.

Eight of the most provocative questions are below, rephrased by me but numbered so you can find their original language if you'd like. All 24 original questions are here. (The NCI wants to be clear that their numbering system is strictly random, presumably so they don't receive eight thousand grant proposals for PQ 1.)

Why are patients with diseases such as Alzheimer's, Parkinson's or Huntington's significantly less likely to get cancer? (PQ 6)
The reverse is also true: People who have survived cancer have a lower risk of developing these neurological disorders. It's unusual to study anti-correlations rather than correlations--usually we want to know what makes us more likely to be sick. But teasing out the molecular and cellular mechanisms that prevent cancer patients from developing Alzheimer's, and vice versa, would teach us a lot about cancer--and about these other illnesses.

How are obesity and cancer connected? (PQ 1)

Obese individuals have a greater risk of many types of cancer. But scientists don't know what, specifically, connects cancer and obesity. It's also unclear whether losing weight lowers a person's risk of cancer. Once someone becomes obese, has the carcinogenic switch already been flipped? Are some risks reversible?

What does an animal's lifespan have to do with cancer? (PQ 7)
In humans, most cancers are diseases of aging. Young people with cancer are a relative rarity; as we use up more of our 80 or so years, our cancer risk rises. In animals that are susceptible to cancer, their disease looks similar to ours. But their lifespans can be radically different. Mice only live about 2 years, yet we can easily model cancers in them. Dogs can develop cancer within their 15 or 20 years of life.

Not all animals have a cancer problem, though. Sea turtles can live for at least as long as humans, if not decades longer, and seem to almost never get cancer. We clearly have a lot to learn about how animals, including humans, age. We also have yet to elucidate the ways in which cancer is, and is not, a disease of aging.

How many cancers are caused by viruses? (PQ 12)
The discovery that viruses caused most cervical cancers led to the development of an HPV vaccine. Some other cancers are known to be linked to viral or bacterial infections. By finding out which types of cancers come from catchable agents, we can learn more about how tumors form and might even be able to create new cancer vaccines.

Why do some types of cancer cluster in geographic regions? (PQ 2)
Your risk for some cancers varies depending on where you live--and if you move, your risk will change. Which of these cancers are being caused by a toxin or other environmental factor? Which are caused by cultural factors such as diet?


Can we find extra-tiny tumors? (PQ 13)
Current imaging technology already has a pretty impressive resolution; doctors can spot tumors that are just one cubic millimeter in size. But could improved technologies reveal tumors that were orders of magnitude smaller? What about a single tumorous cell?

Why do cancer survivors have a higher risk of developing a second cancer? (PQ 15)
Some of a former cancer patient's risk might have to do with the chemotherapy and radiation she or he has already undergone. But if there's more to the story, it might reveal underlying factors that put a person at risk for all cancers--not just cancer of the stomach or skin or prostate.

Could we quantify a person's cancer risk? (PQ 3)

Perhaps in the future, a tool or test in the doctor's office could analyze a blood sample and report back on your current risk of developing cancer, based on carcinogens or metabolic products in your body. Or we could keep sensors in our homes--or wear them on our bodies--that measure our cumulative exposure to carcinogens. What if everyone wore a cancer watch that counted down their healthy days? (You're free to use that idea for a dystopian science-fiction novel. But please send me a copy.)

Is the Aging Brain Uniquely Human?

Even if you stay free of Alzheimer's disease, the normal aging process is fairly destructive to your brain. Neurons disappear, connections lose their strength, protein gunk builds up, and the whole brain shrinks. Areas controlling learning and memory are among the hardest hit. A new study claims that our crumbling brains aren't just a fact of normal aging. Instead, they may be unique in the animal kingdom, the result of an evolutionary bargain our species has struck.

Chet Sherwood at George Washington University led the study, which put humans and captive chimpanzees of various ages through MRI scanners. The humans ranged from ages 22 to 88. Chimps were between 10 and 45 years old, because 45 years is about as long as chimps can live in the wild (more on that in a moment).

In humans, the researchers found a pattern of decreasing brain volume throughout life that accelerated into old age. That pattern was missing in chimpanzees, whose brains seemed to maintain a consistent size.

Chimpanzees were used because they're our closest living relatives; we've been apart for only about 6 million years of evolution. The authors reason that because chimps' brains don't shrink as they age, our own brain degeneration must be a product of our recent evolution. We've developed brains that are big and energy-hungry, and to judge from our global population size, throwing our resources into our noggins seems to have been a good evolutionary strategy.

Since splitting from our ape relatives, we've also evolved longer life spans. Women, in particular, are a curiosity because they can live decades past their fertile years. Evolutionary biologists have hypothesized that keeping infertile elderly women around is no accident, because these grandmothers can bolster the success of their own genes by helping to take care of their grandchildren. The authors of the chimp study suggest that these helpful grandmothers are to blame for our degenerating brains: we've evolved long lifespans and brains that can't quite keep up.

The grandmother hypothesis, though, is hard to prove. And though 45 is elderly for a chimpanzee in the wild, the authors acknowledge that chimps under medical care in captivity can live into their 60s. Is a human today who lives into her 80s, thanks to medical care and disease prevention, comparable to a chimp in the wild? Or is a human "in the wild" better represented by someone in a southern African country with a life expectancy in the 30s or 40s?

If this study included chimpanzees at the true upper end of their age potential, it might provide more insight. The authors acknowledge that some previous studies have shown different results; for example, a study of brain mass that included chimpanzees up to age 59 did find some shrinkage with age.

The authors assume our damaging brain decline is a byproduct of evolution, but don't ask whether it might come from extending our life spans even further than evolution intended. Some perspective might come from studying another animal that no longer lives "in the wild": domestic dogs. Wolves live six to eight years in the wild, but many kinds of pet dogs can live for twice that long.

Even though they're not close to us in evolutionary terms, dogs age much like humans do. Their brains shrink in old age, especially in the prefrontal cortex and the hippocampus--the same areas that are particularly vulnerable in humans. Dogs develop cognitive problems and behavioral changes. Their brains even accumulate deposits of amyloid-beta, the protein gunk that appears in humans and is linked to Alzheimer's disease. Maybe our aging brains are not only the result of our exceptional smarts, then, but also of our domestication.


Sherwood, C., Gordon, A., Allen, J., Phillips, K., Erwin, J., Hof, P., & Hopkins, W. (2011). Aging of the cerebral cortex differs between humans and chimpanzees Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1016709108

To Live Longer, Be a Happy Ape

Orangutans that achieve their goals, enjoy swinging with others, and always look on the bright side of the banana have longer lifespans than those who merely mope around the zoo. That's the conclusion of a long-term study of over 180 captive orangutans. The unhappy apes died sooner, and the happy apes lived to gloat about it.

Alexander Weiss at the University of Edinburgh and his colleagues collected data on captive orangutans in parks around the world. At the beginning of the study period, employees at each zoo who were familiar with the orangutans there rated the apes on their apparent happiness. Questions included how often each orangutan seemed to be in a positive or negative mood, whether it enjoyed social interactions, how well it was able to achieve its goals, and "how happy [raters] would be if they were the orangutan for a short period of time."

Over the next seven years, the researchers kept track of which orangutans had died. Though orangutans in captivity rarely live past their 30s, their aging process is similar to humans'.  And, as in humans, females tend to outlive males.

So it wasn't surprising that more male orangutans died during the course of the study. But the researchers also found that orangutans rated as happier at the beginning of the study were less likely to die over the seven years that followed.

One standard deviation in happiness, they found, was worth about five and a half added years of life. That means the difference between a pretty happy orangutan and a pretty unhappy orangutan is 11 years of living--no small change when you can only hope for 30 to 35 years to begin with.

What could cause unhappy apes to die younger? One possibility is that apes appearing less happy are already ill in some subtle, pre-symptomatic way. Another explanation is that a positive attitude evolved through sexual selection, like a set of showy tail feathers, as a signal to potential mates that Suzy or Sammy Sunshine has good genes. (Though being able to live into old age presumably isn't as important to potential mates as just living long enough to make some baby apes.)

A third possibility is that unhappy orangutans are experiencing more stress in their life, or have a poor ability to handle stress. Our bodies react to stressors by activating a hormonal system that gears us up to fight or flee whatever real or figurative predator is chasing us. It's a survival mode in the short term, but keeping that mode switched on in the long term is damaging to our bodies. Unhappy apes may have their lives shortened by stress.

The authors note that in orangutans, as in humans, happiness doesn't rely on outside circumstances. Part of it is inherited: you're born with your personality. But genes aren't fate, and aiming for a positive attitude--or the fruit on the high branch--might keep you swinging around the jungle into old age.

Image: harrymoon/Flickr

Weiss, A., Adams, M., & King, J. (2011). Happy orang-utans live longer lives Biology Letters DOI: 10.1098/rsbl.2011.0543

10 Billion R Us?

How many humans can fit on Earth?

It's not a logistical question (heel-toe, or nose-to-nose?). It's a question of resources. Every other species on the planet lives with a natural limitation. Say you're a snail that lives in a scummy pond and eats algae. There's plenty of algae available, and soon there are snails everywhere. But as your population booms, and you start bumping shoulders with other snails more often, you find there's not enough algae to go around. A lot of snails die or fail to reproduce. The algae population rebounds while the snail population fades, and the cycle continues.

Humans have beaten this system--for now. We clear forests, irrigate deserts, and blow the tops off of mountains to get the resources we need. This means we've stretched our upper limit. And according to a new report from the United Nations, there's no end in sight.

Previously, the UN had predicted that the world's population would reach 9 billion during this century, then level off. The projected upper limit wasn't because we were due to run out of food or space, though. Demographer John Bongaarts says in an interview with ScienceInsider that the UN's projection, which they revisit every two years, comes from a combination of mortality rate and fertility rate: how quickly are people dying, and how many babies are they having?

As nations invest money in family planning and women gain access to birth control, the fertility rate (how many children the average woman has) tends to decline. Bongaarts says that in Africa, where most of the world's "high-fertility" countries are, there has been a lack of investment in family planning programs recently. The Bush administration, for example, cut funding for contraceptives to African nations. Additionally, Bongaarts says AIDS hasn't affected population growth in Africa quite as researchers expected it to.

The result is that the UN now expects the world's population, rather than peaking around 9 billion, to continue on to 10 billion by the end of this century. And there's no peak--the population will still be increasing in 2100.

To come up with their projections, the UN says, "Account is taken of past fertility trends in a given country plus the past experience of all other countries in the world. The model was used to generate 100,000 trajectories for future fertility for each country." Out of those 100,000 projections for each country, they used the median values to make an overall projection.

The UN's model assumes that over time, the low-fertility and medium-fertility countries will level out to their "replacement rate"--that is, each generation will have enough children to exactly replace itself. For a country where most people make it to adulthood, that means 2.1 kids per mom. Low-fertility countries include most of Europe, as well as Iran, Brazil, and (by design) China. Countries with intermediate fertility include India, Mexico, Egypt, and the United States. High-fertility countries include 39 African nations.

A small wobble away from the predicted fertility rates could have a huge impact on the global population. The UN report points out that if they've overestimated global fertility by half a child per woman, the population will peak at 8 billion and swing downward again to 6 billion by the end of the century. But if they've underestimated by a half a child, we could hit almost 16 billion by the year 2100.

Mortality is important, too. It's assumed that life expectancy will continue to increase globally. The highest-fertility countries also happen to be some of those with the lowest life expectancy, thanks to killers such as HIV and malaria. Currently, life expectancy among all high-fertility countries is just 56 years. (Low-fertility countries, where people presumably have the best access to health care, have the highest life span: 74 years, compared to 68 years for those of us in the middle group.)

All these projections, too, hinge on there not being a global cataclysm in this century that removes a large portion of our population, as the Black Death or the 1918 flu pandemic did. Just because it's the twenty-first century doesn't mean this risk is gone. Viruses are mutating all the time, bacteria are developing resistances to most of our antibiotics, climate change is altering the life cycles and habitats of animals that carry diseases--and, of course, people are getting closer together.

What's the lowest global population you remember? The world reached 3 billion people in 1959, and 4 billion in 1974. In 1987 we reached 5 billion. I remember hearing from Bill Nye (the Science Guy) that the population was almost at 6 billion; it reached that number in 1998. We're currently expected to hit 7 billion this fall, 8 billion in 2025, and 9 billion in the 2040s. Get ready to bump some shoulders.

Muscle Memories

Let me tell you about one of the dumbest workouts I've ever seen.

No, it wasn't somebody doing sprints in Shape Ups. Last week I saw an oldish man in my building's workout room, wearing khakis and a plaid button-down (always a red flag). When I arrived, he was doing bicep curls with 3-pound weights, one in each hand. Aw, I thought, he has to use really light weights because he's older. And he's counting out loud because he can't remember how many reps he's done! (It was 20.)

Then he put down the 3-pound weights and picked up the 5-pounders, and did the same 20 bicep curls. Then the 8-pounders: 20 bicep curls. Sure enough, standing in front of my elliptical machine, he worked his way down the entire rack of free weights. Then he moved to the heavier weights on the other wall. "Unh...one! Unh...two!" He grunted through sets of 20 bicep curls on increasingly giant dumbbells. Then suddenly he was holding a stretchy rubber cord with handles. He stepped on the cord with his right foot and stood with one end in each hand. Don't do it, I thought. He did a bicep curl. "One!" Twenty curls later, he switched feet.

The moral of this story--besides that I now know exactly how many pieces of equipment in our workout room can be used for a bicep curl--is that some workouts are obviously counterintuitive. Why waste your time on 3- and 5-pound weights when you can lift 25-pounders? (And how big do your biceps need to be if they're the only part of your body you're working out?) If you've ever exercised, you can feel that your body gets stronger only as you challenge it.

Muscle cells don't look quite like those textbook fried-egg cells, with a nice round yolk in the middle and a bunch of goo outside. Instead, they're very long fibers that can have many nuclei. When you exercise, your stressed-out muscle fibers absorb some of the little helper cells that live around them. Then the extra nuclei (it seems) help your muscle fibers grow thicker.

In a new study, Norwegian scientists made mice exercise a certain muscle for three weeks, and observed the extra nuclei--54% more than the mice started with--being added to the muscle fibers. After the nuclei started to increase, the muscle fibers increased in thickness.

The scientists worked another group of mice for two weeks and then severed the nerves connected to the muscle, forcing it to atrophy. They found that even though the muscle fibers shrank dramatically, the number of nuclei stayed essentially the same over the following two weeks. Even three months later, there were still extra nuclei in the muscle fibers.

This might be the reason, they say, why it's easier to gain muscle where you've had muscle before. Even if you haven't exercised in a long time, you're not starting from scratch because you might still have extra nuclei in your muscle fibers. The authors point out that three months is a pretty long time for a mouse, which only lives a couple of years. So who knows how long the effect might last in humans?

Athletes who are known to have used steroids in the past are still allowed to compete--but what if it turns out that steroids give muscles a boost that lasts for many years? Even if previously bulked-up steroid users seem to have returned to normal, what if their muscles retain extra strength or efficiency? "The benefits of using steroids might be permanent," the authors say. Should everyone who's ever used steroids be banned for life?

The authors also suggest that by "filling up" muscles with nuclei earlier in life, people could prevent some of the weakness that comes with old age. Once people are older, it's much harder for them to build muscle mass--no matter how many bicep curls they do.

What Happens to Chatterboxes

Do you have videos of yourself at age seven? If so, you can probably see predictors of your current personality in your miniature self. A new study from a graduate student at the University of California, Riverside, says that certain personality traits in elementary schoolers are linked to certain other traits in middle-aged adults.

Psychology student Christopher Nave culled his data from a (very) long-term study that began in Hawaii in the 1960s. Elementary school teachers rated 2,400 students on dozens of personality traits: Is the student adaptable (copes easily and successfully with new and strange situations)? Is the student spiteful (deliberately does or says things that annoy or hurt others)?

Forty years later, researchers started hunting down these former students. So far, they've brought back about 450 of them. (Where did everyone go?) These good sports completed various tests and interviews, and out of those, Nave compared 144 who'd agreed to be videotaped and whose teachers had rated them on the same traits.

Based on their taped interviews and personality surveys, the adults were rated on 67 different traits. Many of the kid traits turned out to be strongly correlated with adult traits, and the researchers described four that were the most distinctive:

Verbal fluency, to psychologists, apparently means "chattiness" rather than "ability to speak one's native tongue." Adults who had been rated verbally fluent as kids were found to be smart, ambitious, controlling, and interested in intellectual matters. Kids who were adaptable became adults who are cheerful and sociable. Impulsive kids ("often acts before the appropriate moment; finds it difficult to hold back") were more likely, as adults, to be loud and energetic. And kids described as self-minimizing ("humble; never brags or shows off") were likely to seek reassurance and express guilty feelings as adults.

Maybe this is bad news for parents who were hoping they could teach their kid to be less impulsive. Or maybe it lets them off the hook a little. After all, if your kid's personality is already set at age six or seven, then there's not much you can do about it. (Half the kids in the analysis were in first or second grade, and half were in fifth or sixth grade. But these correlations were all found to be independent of grade level.)

Don't you wish you knew how your younger self measured up? It's like checking yesterday's horoscope to see if it came true. Or maybe you have a good sense of what you were like as a little kid. I remember my dad calling me a "chatterbox" in kind of a strained tone, so I'm guessing I talked a lot. According to the study, that means I'm less likely to seek advice now. Is that true? Do you think I should do something about it? Wait, no, don't tell me.

Why Do Kids Hate Polar Bears?

I have an email folder labeled "Angry Mail." It's not exactly bursting at its digital seams, but every once in a while I have to answer a letter from a reader who's upset about something. (Someone else answers all the friendly mail; I only get the nasty stuff.) So yesterday I finally dealt with one that had been sitting there for a few weeks. Its subject line was: Geoengineering and "Global Warming."

You can probably guess from the scare quotes that this reader, a girl of unspecified teen age, doesn't believe in climate change. We ran a cover story about geoengineers, scientists who are proposing drastic physical measures (cloud seeding; giant space umbrellas) to counteract global warming. Anonymous Reader disagrees with our premise: "I really think the geoengineering article in the April issue was totally one-sided. It didn't acknowledge that some of the things the author presented as scientific fact are either controversial or DISPROVEN!"

Teens love exclamation points and caps-lock, by the way. They also love putting little stage directions in asterisks, like this: *goes off on tangent*

This girl included links in her email to pages at both the London Times (saying it "disproved" glaciers shrinking in the Himalayas) and NASA ("global warming DID NOT cause ice to melt in the Arctic!"). Concerned, I followed both links. The Times story was about an infamous gaffe in which some scientist guessed, without having supporting data, that the Himalayan glaciers would all be melted by 2035, and a bunch of important people quoted him before someone realized the number was totally made up and also impossible. The glaciers will take a long time, maybe hundreds of years, to totally melt. But the article also makes clear that the glaciers are, in fact, melting.

The second link was to an article about weird winds that are contributing to melting Arctic sea ice. The article doesn't say anything explicit about climate change, probably because NASA assumes it is blindingly obvious that global warming is the major contributor to the ice melting. Once sea ice is thinned and broken up, wind that blows ice floes south will make them melt even faster. If this girl were looking for NASA's data on global warming and polar ice caps, she could have found it in one or two clicks.

So where is she getting these willful misinterpretations? A blog written by a meteorologist, which she helpfully sent me a link to. Did you know that fewer than one third of TV weathermen believe in human-caused climate change? I guess all that snow confuses them. I wanted to tell this girl to consider her sources; anyone can write a blog. (!) But her generation has grown up with reality TV, Facebook, Twitter, and YouTube commenters. Any moron with an opinion can make himself heard loud and clear.

I sent her some more links to read; she probably didn't. I wish she had been the first juvenile climate-change skeptic I'd heard from, but she was far from it. Are all kids such cynics? When I was little I believed in EVERYTHING! (See, I can do it too.) At various times in my childhood I believed that Santa Claus existed, that a friendly poltergeist was following me, and that if I just tried a little harder I would finally tap into my powers of ESP and telekinesis. When I was very young, a bishop visited our parish and I misunderstood and thought he was God. To be fair, he had a really fancy hat.

I also believed that if my friend and I spent enough time picking up trash and making pinecone bird feeders, we would SAVE THE EARTH! We painted it on bookmarks and stationery. I convinced my parents to let me put a water-saving milk-jug contraption inside our toilet tank. I would rather have given up all my PBS privileges than littered.

So what happened? Was I the outlier? I know it's always been uncool to care. But the hostile dismissal of science ("Those 'scientists' are government funded idiots," says another teen reader) scares me. It's not going to be enough for me to care. It wouldn't even be enough for all the adults to care. The kids who are growing up into a world of rising oceans, vanishing species, and terrifying new diseases are going to have to care. The best I can do is to keep sending them my emails, even if it makes me hopelessly uncool. *is really thankful not to be in high school anymore*