Higher Altitude Protects Teens from Concussions

The human brain is a vulnerable thing, perched in its peanut shell on top of our walking, stumbling bodies. Humans who enjoy collision-heavy pastimes—say, tackle sports—put their brains in particular danger. And when it comes to concussions, young people are at even more risk than adults. Yet kids who play at at higher altitudes seem to be safer than their peers. The reason, hidden somewhere in the brain's squishy dynamics, might help protect kids and adults who are smashing into each other everywhere.

You don't have to travel to Denver's Mile High stadium for your body to start responding to altitude. "Relatively small changes in altitude can have significant changes upon the physiology of the body," say Gregory Myer and David Smith, both in the sports medicine department at Cincinnati Children's Hospital Medical Center. (The coauthors responded to my email jointly.)

At just 600 feet above sea level, the authors point out, oxygen in the atmosphere has already dropped from 21 percent to 20 percent. Your body notices this slight change and adjusts. One measure it takes, upon noticing there's less oxygen available than usual, is to send a little more blood to your brain. "This leads to a slight filling up of the brain space," Myer and Smith say. Your brain ends up squeezed just a tad more tightly into your head.

Wherever you are, if you get suddenly knocked on the head, your brain will ricochet around inside your skull's fluids. In actual scientific terms, it "sloshes." The delicate brain squishes and twists, and hosts of neurons fire all at once. You may black out. Afterward, you might have memory loss, confusion, nausea, dizziness, and other symptoms that can last for days or months. The looser, stretchier blood vessels in the brains of people under age 20 may explain why they're at even greater risk.

Concussions might be prevented if the skull could keep the brain from sloshing by holding onto it a little tighter—as it does at higher altitudes. To find out whether this works, Myer, Smith and their colleagues used data from the National High School Sports-Related Injury Surveillance System. Run by the University of Colorado, Denver, this study collects data on injuries from high schools across the country.

The authors looked at nearly 6,000 concussions from about 500 schools. The concussed kids were athletes in all kinds of sports, at schools ranging from sea level to 6,900 feet. When the researchers divided student athletes into those living above and below the median altitude—which was 600 feet—they saw a significant difference in concussions. Across all sports, kids at higher altitudes had a 31 percent lower risk of concussion. Among football players only, the results were essentially the same: a 30 percent lower risk at higher altitude.

It's an intriguing difference. As sports organizations and the public learn more about chronic traumatic encephalopathy (CTE) and the long-term risks for athletes with head injuries, the quest to prevent concussions is growing more urgent. High schoolers, though, don't travel to play like professional athletes do. Could some of their lower risk have to do with changes in their bodies that happen over a lifetime of living at a certain altitude? "Visiting altitude will begin creating a tighter fit the minute you arrive," Myer and Smith say. However, adjustment happens over the long term too. "Everyone is likely different in how quickly they respond [to altitude] and how protection occurs for them," the authors say. "This is why we are working to evaluate technologies that can give this same protection whether you are in Denver or Miami." They'll be looking next at adults and professional athletes to try to find answers.

One hint comes from an earlier study David Smith performed on rats. While wearing a collar that slightly squeezed their jugular veins, the rats were hit hard on the head. The collar seemed to make rats less vulnerable to concussion, apparently because more blood was in their heads, squeezing their brains more tightly and preventing sloshing. This all sounds pretty unpleasant for the rats, but Myer and Smith insist that "the technologies we are studying are no more risky than yawning or even the act of lying down."

Animals like woodpeckers and head-ramming sheep manage to protect their brains from damage, the researchers point out. So why can't we? Of course, in our case the head ramming is in the name of fun. But there might be ways to safeguard our brains, like these animals do, from the inside out.


Image: Rocky Mountain High School in Colorado, by Paul L. Dineen (via Wikimedia Commons)

David W. Smith, Gregory D. Myer, Dustin W. Currie, R. Dawn Comstock, Joseph F. Clark, & Julian E. Bailes (2013). Altitude Modulates Concussion Incidence: Implications for Optimizing Brain Compliance to Prevent Brain Injury in Athletes. Orthopaedic Journal of Sports Medicine DOI: 10.1177/2325967113511588

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

Found: A Rotten-Smell Button in the Brain

Window or aisle? Hamburger or hot dog? Bouquet of flowers or rotting flesh? Not all your preferences are up to you—some have been hammered into your genes by evolution.

If you're an average human, you avoid the smell of decay. It signals unsafe food and the threat of infection or disease. Other animals run toward the stench of a stale carcass, maybe because they're flies and it signals a place to lay their eggs.

Whether they love it or hate it, animals identify the scent of rot from two signature molecules. German doctor Ludwig Brieger discovered these molecules in the late 1900s; in English, they're rather cutely named "cadaverine" and "putrescine." Bacteria create the two culprits by breaking down down amino acids in animal bodies. Not solely the sign of a rotting carcass, cadaverine and putrescine also show up in urine and bad breath.

Despite the importance of these smells (or avoiding these smells) in animals' lives, no one had found receptors for these molecules—that is, the locks to which the molecules are keys. Scent receptors are attached to one end of a neuron inside the nose (or whichever body part an animal smells with); when a certain chemical wafts up the nose and latches onto the receptor, a signal travels along the neuron to the brain at the other end. Researchers at the University of Cologne in Germany and Harvard University think they've found one of those receptors for rot.

The authors, led by the University of Cologne's Ashiq Hussain, studied zebrafish, which are commonly used to model the sense of smell in vertebrates. First they checked to make sure zebrafish respond to the smell of decay. When they put putrescine and cadaverine into a tank, zebrafish swam to the other end, showing they feel the same way we do about these smells. When the authors plugged the zebrafishes' little nostrils with glue, the fish were no longer bothered by the odor.

The researchers searched for a receptor in a family of proteins called TAARs (trace amine-associated receptors). Related receptors in rodents are thought to detect other unpleasant odors that come from living things. Zebrafish make 112 different kinds of these receptors, but the molecules that attach to them hadn't been found yet.

After testing 93 smelly chemicals on representative zebrafish TAARs, the authors found a match: cadaverine turns on a receptor called TAAR13c. But could the receptor detect cadaverine in real life, and not only when it was dripped on in purified form by a scientist? To test it, the researchers used an extract of dead fish. When exposed to liquid made from a recently deceased zebrafish, the receptors didn't respond. Liquid from a week-old, rotten fish carcass, though, easily activated the receptor—even when diluted to 1 part in 1,000.

Finding a receptor for cadaverine means scientists now understand a little bit more about how the vertebrate brain responds to awful smells. The receptor protein itself "will not be similar in humans, because mammals do not have close relatives of this zebrafish receptor," says Sigrun Korsching, the paper's senior author. Still, she adds, "There are very few cases where you can show activation of a single receptor leads to a behavioral response." Studying how the zebrafish's neurons respond to cadaverine could lead to a better understanding of how animals process all kinds of odors, whether they enjoy them or not.

Image: by Bill Gracey (via Flickr)

Ashiq Hussain, Luis R. Saraiva, David M. Ferrero, Gaurav Ahuja, Venkatesh S. Krishna, Stephen D. Liberles, & Sigrun I. Korsching (2013). High-affinity olfactory receptor for the death-associated odor cadaverine. PNAS DOI: 10.1073/pnas.1318596110

Note: This post has been edited from an earlier version.

Snoozing on the Weekend Won't Undo Workweek Sleep Loss

Does your workweek schedule dig you into an ever-deepening hole of sleep deprivation? Do you sleep in on the weekends to try to boost yourself back out? You're in good company. But even if you feel recovered by the following week, your brainpower might be suffering.

In a survey by the National Sleep Foundation, 40 percent of respondents said they try to "catch up" on sleep during the weekend. Pennsylvania State University professor and physician Alexandros Vgontzas, along with a group of colleagues, recruited 30 subjects to study how well this catching up really works. The subjects were healthy men and women between 18 and 34 (who didn't mind the prospect of sleeping with a catheter in their arm).

For two weeks before the study, researchers made sure subjects got 7.5 to 8 hours of sleep every night. Then the subjects came into the sleep lab. The experiment began with three "baseline" nights of 8 hours' sleep. For the next five nights, their sleep was restricted to just 6 hours, mimicking a full workweek of uncomfortably early rising. Then subjects had two "recovery" nights where they were left sleeping for 10 hours.

During most days of the experiment, subjects were allowed to go home and follow their normal routine—though monitors on their wrists made sure they followed strict no-napping instructions. At night, they returned to the lab. And after each phase of the experiment, subjects spent a full 24 hours undergoing tests: researchers tracked the levels of hormones circulating in their blood and gave them cognitive tests. They also asked subjects to rate how sleepy they felt. To measure their actual sleepiness, researchers had subjects lie down to nap, recorded how long it took them to conk out, and woke them up again—six times a day.

Predictably, subjects were sleepier during their week of sleep deprivation. It took them less time to fall asleep during the day, and the easiest time for them to nap was 9:00 in the morning (as opposed to 3:00 in the afternoon during the baseline period). After their two recovery days, subjects' sleepiness returned to normal.

One hormone the scientists monitored was IL-6, a marker of inflammation in the body. They found that IL-6 increased when subjects lost sleep. This fits with what earlier studies have found, and suggests one way sleep deprivation is bad for your health. IL-6 levels dropped back to normal after the two nights of recovery sleep.

The only measurement that didn't go back to normal was performance on a test called the psychomotor vigilance task (PVT). Subjects did this test every two hours during their lab days. In it, they watched a screen for ten minutes and pressed a button every time a certain number appeared. It's a test that measures a person's ability to sustain attention; astronauts on the International Space Station do a similar test on themselves to check for fatigue.

Subjects in the sleep study did worse on the PVT after their sleep-deprived week, and continued to do poorly even after two nights of catch-up sleep. Vgontzas says he doesn't know why this is. But apparently some function in people's brains hadn't recovered fully by the end of the experiment, even though they felt well rested.

It's worth noting that because there was a 24-hour testing period after each stage of the experiment, subjects actually had a sixth night of poor sleep before their "weekend." And some champion snooze-button users can sleep well past 10 hours on their real makeup days. Still, Vgontzas's findings suggest our brains are slow to catch up after losing sleep—specifically, our ability to pay attention suffers—and we might not know when we're mentally fatigued.

Vgontzas also doesn't know what the cumulative effect might be of living this way every week. On average, he writes, we need seven hours of sleep a night. (Though if you really can't sleep any later, a nap during the day will also help you recover.)


Image: by Phae (via Flickr)

Pejovic S, Basta M, Vgontzas AN, Kritikou I, Shaffer ML, Tsaoussoglou M, Stiffler D, Stefanakis Z, Bixler EO, & Chrousos GP (2013). Effects of recovery sleep after one work week of mild sleep restriction on interleukin-6 and cortisol secretion and daytime sleepiness and performance. American journal of physiology. Endocrinology and metabolism, 305 (7) PMID: 23941878

Unempathetic Kids Don't Get Sarcasm

A crucial tool in your social survival kit is the ability to tell when someone means the opposite of what they're saying. For centuries, writers have tried to aid readers' detection of sarcasm with various typographic contortions: backward question marks, upside-down or zigzagged exclamation marks, even left-leaning italics dubbed "ironics."* (None of these have stuck, probably because pointing out when you're being sarcastic totally ruins it.)

For kids, sarcasm is a developmental hurdle to clear. At some point while they're growing up, they learn that positively worded statements—"Wow, great job"—aren't always positive. When psychologists at the University of Calgary began their recent study of kids and sarcasm, they started with a group of 6- and 7-year-olds. They expected that the children would be just beginning to grasp the skill. But when these kids showed "near-zero accuracy" at detecting irony, the researchers had to try again.

Thirty-one 8- and 9-year-olds became the new study group. For the experiment, each kid watched a series of 12 short puppet shows. The shows involved two puppet characters and ended with one of them saying either "That was so good" or "That was so bad"—sometimes literally and sometimes sarcastically. For example, one puppet misses a soccer goal; the other says, "That was SO GOOD." (A separate panel of adults had vouched for the sarcastic tone of the recorded dialogue.)

Kids had to decide after each show whether the final line of dialogue was nice or mean. They indicated their answers by picking up either a small plush duck or shark. (The actual niceness or ironic tendency of these animals was not addressed in the study.)

When the puppets' statements were literal, kids had no difficulty interpreting them as nice or mean. But the sarcastic statements gave them more trouble. Their accuracy as a group was a little under 50 percent; the researchers explain that about half the kids seemed to get it consistently, while the other half were "quite inaccurate" at spotting sarcasm.

Subjects' parents also filled out questionnaires about how empathetic their children were—a good understanding of other people's emotions might go along with an understanding of when people are being shark-ish or duck-ish. Kids with higher empathy scores did better in the sarcasm test. Additionally, explains senior author Penny Pexman, video footage revealed that kids with better empathy were slower when reaching for the wrong toy than their less empathetic peers. In other words, when empathetic kids failed to find the sarcasm, they struggled more with their answers. They may have sensed that there was another layer to the puppet's words: was that missed soccer goal really "so good"?

"We need to offer children extra supports when we use sarcasm," Pexman says. A second- or third-grader might have only a dim understanding of your clever one-liner. A first-grader will likely miss it entirely.

Additionally, "Encouraging children to be more empathetic has great benefits for understanding sarcastic speech," Pexman says. "We know from other research that empathy helps with other aspects of social functioning too." I mean, I GUESS that's a good thing.


*I learned about ironic punctuation in Keith Houston's book Shady Characters. There are a lot of good tidbits in there, from ampersands to octothorpes. The chapter on irony is summarized at Brain Pickings.

Image: by Spamily (via Flickr)

Andrew Nicholson, Juanita M. Whalen, & Penny M. Pexman (2013). Children's processing of emotion in ironic language. Frontiers in Psychology DOI: 10.3389/fpsyg.2013.00691

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

Fish Fear Robotic Predators, Unless They're Drunk

Scientists swear they had a really good reason for building a robotic fish, getting some other fish drunk, and then chasing them around with it.

The robotic bird head, too.

Researchers at the Polytechnic Institute of New York University and the Istituto Superiore di Sanità in Rome were interested in zebrafish. These thumb-sized, striped fish are laboratory favorites because their genome is well understood, they reproduce quickly, and their embryos are totally transparent.

One area of research that employs zebrafish is the study of emotions, including anxiety and fear. Outside of a lab, people may not spend much time pondering fish anxiety. But study coauthor Simone Macrì of the Istituto Superiore di Sanità says zebrafish can help unravel complex environmental and genetic interactions, such as emotion, because their genetics are not a mystery. Their simple brains are useful for "clarifying some fundamental aspects [of] emotions," he says.

It's easy to spook a little fish; all you have to do is show it a predator. But wrangling live predatory animals such as birds or other fish is inconvenient. It also adds an unwanted variable to an experiment, since your predator may not behave consistently (or may have moods of its own). So Macrì and his colleagues wondered if they could build robotic predators good enough to be stand-ins in these experiments.

They carefully crafted robots that looked like a natural zebrafish enemy, the Indian leaf fish. ("The visual appearance of the robotic fish was obtained by spray-painting the robot with an ivory base color followed by the hand painting of brown color patterns typical for this species," the authors write—in case this is a project you want to try at home—"as well as the attachment of small plastic eyes.") A motor let the robot fish wave their tails at various speeds. There was also a robotic heron head that plunged toward the water as if hunting.

To find out whether their robots made the same impression on zebrafish as a real predator, the researchers let the animals meet each other. Sure enough, zebrafish swam to the far side of their tank when a robotic leaf fish was in the water. When a robotic heron struck from above, zebrafish darted under a shelter.

Then, to make sure the fish were responding to the robots out of fear or anxiety, the researchers gave the zebrafish a drug that reduces anxiety: alcohol. After letting their subjects swim around in ethanol-spiked water, the researchers gave them the same tests. Now they didn't flee the robot fish and were slow to seek shelter after the robotic heron attack.

As the researchers had hoped, sober fish feared robotic predators, and alcohol lessened those fears. The results are published in PLOS ONE.

Macrì thinks this technique could help researchers who study anxiety with zebrafish improve their methods. As long as scientists are looking at simple behaviors, he says, "the robots are ideally suited." And after being chased by a giant robotic predator, zebrafish might need a drink anyway.


Images: left by Azul, via Wikimedia Commons; right Cianca et al. (In reality, the robotic fish were several times larger than the zebrafish.)

Valentina Cianca, Tiziana Bartolini, Maurizio Porfiri, & Simone Macrì (2013). A Robotics-Based Behavioral Paradigm to Measure Anxiety-Related Responses in Zebrafish PLOS ONE DOI: 10.1371/journal.pone.0069661

Man Develops Synesthesia after Stroke, Finds James Bond Theme "Orgasmic"

It wasn't only James Bond. Nine months after suffering a stroke, a 45-year-old happened to notice that the wailing horns in a Bond movie's opening credits gave him strange, ecstatic feelings. But any high-pitched brass instrumentals would do the trick. A musical segment during the Beijing Olympics gave him the same feelings. The man's doctors came to realize that when his brain rebuilt itself after the stroke, he had developed synesthesia.

Associating letters or numbers with specific colors is the most common kind of synesthesia. Other sensory combinations, like experiencing tastes when hearing certain sounds, are rarer. In some cases, colors, sounds, or other sensations may trigger emotions.

The recovered stroke victim, whom doctors and researchers at St. Michael's hospital in Toronto described in the journal Neurology, turned out to have more than one trigger for his emotional synesthesia. High-pitched horns gave him very good feelings, but words written in the color blue made him feel "disgusted." Yellow words were also disgusting, though a little less so.

To confirm what the patient said he was experiencing, the authors did fMRI scans of his brain, along with six non-synesthetic subjects of the same age. All the subjects listened to the Bond theme in the scanner, and their brain activity was compared to what happened when they heard a solo euphonium—a tuba-like instrument that didn't excite the patient at all.

Control subjects responded to the Bond theme no differently than the euphonium, but the stroke victim's brain had a much stronger response to the theme song. The activity in his brain, spread out across many different areas, fit with "intense emotional arousal," the authors write, "rather than simply...a pleasant musical experience." Apparently, the music really was sending him to double-oh-heaven.

In the scanner, subjects also viewed blocks of text written in yellow, blue, or black. While control subjects' brains didn't respond differently to the different colors, the synesthetic man's brain did. His neural activity when reading blue or yellow words suggested he was processing an emotional stimulus, the authors say.

There's only been one other case recorded of someone developing synesthesia in mid-life. That person's experience—a tingling sensation when hearing certain sounds—also came after a stroke. Both patients had damage in the same region of their brains: the thalamus. Tom Schweizer, director of neuroscience research at St. Michael's hospital and the lead author of the paper, says this is significant.

Schweizer describes the walnut-sized thalamus as a "central relay station" for the brain. It's densely packed with fibers that connect neurons in different brain regions. Schweizer thinks that in trying to repair itself after the stroke, the thalamus may have gotten some wires crossed.

The patient's synesthesia isn't exactly like traditional synesthesia, which develops in childhood. For example, he's able to suppress his feelings if he tries, while synesthesia is usually defined as involuntary. Nevertheless, Schweizer says this case "could be a rare window" into how synesthesia develops and the role the thalamus might play.

Even the authors of the study couldn't resist a Bond pun, titling their paper "From the Thalamus with Love." (Why not "License to Thrill"? Or "Dr. No...More Jokes Please; Don't You Know This Makes It Really Awkward When People Invite Me to Jazz Concerts?") Yet his case gives a serious clue as to how the brain's wires can get double-crossed.


Image: Paul-W (via Flickr)

Tom A. Schweizer, PhD, Zeyu Li, BSc, Corinne E. Fischer, MD, Michael P. Alexander, MD, Stephen D. Smith, PhD, Simon J. Graham, PhD, & Luis Fornazarri, MD (2013). From the thalamus with love: A rare window into the locus of emotional synesthesia Neurology DOI: 10.1212/WNL.0b013e31829d86cc

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

Hack Your Workout: These Songs Make People Take Bigger Steps

Do you have a workout playlist? You may find yourself matching the stride of your power walk to the beat in your earbuds—but tempo isn't the only thing affecting how fast you go. Certain musical pieces seem to make people take longer strides, even while walking to the same beat. (Spoiler alert: Aqua.)

Marc Leman is a musicologist at Ghent University in Belgium. With his colleagues, he created a list of 52 songs with a tempo of 130 beats per minute, a speed they chose based on previous research. The playlist included a variety of genres, and all the songs were in 4/4 time.

Then the researchers gathered 18 "normally built" adults, strapped sensors to their legs, and sent them walking laps around a gymnasium. The subjects were explicitly told to walk in time to the beat of the music. Through headphones, they heard 30-second clips of the different songs, with periodic interludes of only a metronome sound.

Although all the music had the same tempo of 130 beats per minute—which subjects stepped in time with—their actual walking speed varied as they took longer or shorter strides. Leman says that to certain songs, people walked 10 percent faster than they did to others (or to the metronome beat).

The researchers dubbed the fastest-walking songs "activating," and the songs that made people walk slowest "relaxing." The full playlist is here, ranked from most relaxing to most activating. These were the top 10 most relaxing songs, to which walkers made the least forward progress:

And here are the tunes to which people covered the most ground:

Right around the middle was "Dragostea din tei," better known by some as "the Numa Numa song." Test subjects probably got slowed down by the requisite arm flailing.

Separately, the researchers asked subjects to rate the musical selections on a variety of adjectives: Was the song happy or sad? Tender or aggressive? Known or unknown to the listener?

Some of the responses were tied to how speedily the songs made them walk. For example, pieces described as "stuttering" rather than "flowing" made people take shorter strides. Pieces that subjects found especially "aggressive" or "loud" (although the volumes of all the songs had been matched in their headphones) made people walk faster. So did songs they described as "bad" rather than "good." (This may explain "Barbie Girl").

The musicologists, meanwhile, tried to find more scientific explanations for the powers of certain songs. Leman says this was surprisingly difficult. They did find that more activating songs tended to have simpler melodies, with fewer notes per beat. These pieces often had a strong bass line, as well as clear downbeats ("one two three four..."). The group is still working on figuring out what kinds of music make people move the fastest.

For his own exercise playlist, Leman is a fan of jazz, though he says it's not always great at getting a person moving. He thinks syncopation, which interrupts the regular beat of the music, is an important factor in making a piece relaxing rather than activating. Instead of marching straight ahead, syncopated jazz music seems to encourage you to walk with more horizontal motion, Leman says: "You want to swing."


Image: by Malingering (via Flickr)

Marc Leman, Dirk Moelants, Matthias Varewyck, Frederik Styns, Leon van Noorden, & Jean-Pierre Martens (2013). Activating and Relaxing Music Entrains the Speed of Beat Synchronized Walking PLOS ONE DOI: 10.1371/journal.pone.0067932

Decapitated Worms Regrow Heads with Memories Still Inside

How good are you at remembering something you learned two weeks earlier? What if during the intervening 14 days, your head was removed? One flatworm isn't bothered by this scenario. After growing back its entire head and brain, it picks off pretty much where it left off.

The planarian is a modest little flatworm, the kind of common microscope denizen you might find in a Gary Larson cartoon. What's remarkable about it is its ability to regenerate. The whole body can regrow, head to eyespots to tail, from even a tiny fragment of the original animal.

Tal Shomrat and Michael Levin at Tufts University built a computerized apparatus for training planarians. Back in the 1960s, an intriguing line of research had suggested that the worms might be able to retain memories after decapitation. But researchers had done their training and testing by hand, a cumbersome method that led to inconsistent results. ("The process of training worms by hand is very time-consuming," Levin says, probably understating it.) Ultimately, the topic was abandoned. Now, with a totally automated procedure, Shomrat and Levin hoped to study planarian memory with less error and greater numbers of worms.

First, their worms spent 10 days getting familiar with one kind of environment, either a regular petri dish or one with a rough floor. They were fed abundantly so that they'd learn a positive association with their home environment. Then, for testing, they were put in a rough-bottomed dish with a little spot of food in the center and a light shining on it. Planarians like to stick to the periphery, and they hate light, so they needed to overcome both aversions to get the food. As expected, worms that were more familiar with the rough dishes reached the food sooner, as measured by video tracking.

When the researchers tested the worms again 14 days later, they found that the worms trained on a rough-bottomed dish were still more comfortable with it than the other worms. This memory seemed to last for at least two weeks. Perfect—that's just enough time for a planarian to lose its head and grow it back.

The worms were relieved of their heads. The scientists made certain that no bit of brain survived. Then, after the worm stumps had painstakingly re-headed themselves, the planarians went back into the testing chamber.

The memory wasn't there right away. But Levin and Shomrat found that if they gave all the worms one quick training session before testing, worms who'd previously been familiarized with rough petri dishes reached the food significantly faster than the other worms. The training session "basically allowed the worms to refresh their memory of what they had learned before decapitation," Levin says. In other words, their memories had survived the loss and regrowth of their heads.

Levin doesn't know how to explain this. He says epigenetics may play a role—modifications to an organism's DNA that dial certain genes up or down—"but this alone doesn't begin to explain it."

It's a mystery, Levin says, how a chemical tweak somewhere outside of a worm's brain can later be translated into information, such as the knowledge that a bumpy environment means food is nearby. "We don't have an answer to this," he says. "What we do show evidence of is the remarkable fact that memory seems to be stored outside the brain."


Image: Shomrat and Levin.

Tal Shomrat, & Michael Levin (2013). An automated training paradigm reveals long-term memory in planaria and its persistence through head regeneration The Journal of Experimental Biology : 10.1242/​jeb.087809

How to Detune Someone with Perfect Pitch

Granted, it's a prank you can play on only 1 in 10,000 people. But if you find one of those rare individuals who can name any note they hear, with just a brief manipulation you can set that power awry. You can later console your subject with a reminder that, after all, nobody's perfect.

A children's choir that I used to sing in always performed the carol "Once in Royal David's City" at a certain concert, and the boy soprano who sang the opening solo would be sent up to a high chapel balcony along with a man who had perfect pitch. The adult would hum the correct note in the boy's ear, apparently, so that he could begin the solo out of a dramatic silence. (Looking back, I'm not sure sending someone up to blow very softly on a pitch pipe wouldn't have accomplished the same thing—but the addition of the superpowered helper made the whole thing more thrilling.)

People with perfect, or absolute, pitch can identify any notes they hear, and can tell you if those notes are a little sharp or flat. Stephen Hedger, a graduate student at the University of Chicago who's studying both cognitive psychology and musicology, has perfect pitch. After discovering that his perception could be skewed distressingly by someone fiddling with a tuning knob while he played the keyboard, he decided to test just how absolute "absolute pitch" really is.

Hedger gathered 13 subjects who'd scored as high as possible on a test of absolute pitch. At the beginning of the experiment, they listened to a series of notes; for each one, subjects had to identify the name of the note and whether it was in tune. The notes included everything from middle C to the B above it, and each note had three versions: one in tune, one slightly flat, and one slightly sharp.

(The out-of-tune notes were off by 33 "cents." The distance between any two notes, say C to C#, is 100 cents. Most people can detect a difference of just 25 cents, so a 33-cent difference—a third of the way to the next note—would be comfortably noticeable to all but the tone-deaf.)

Next, subjects listened to the entirety of Brahms's Symphony No.1 in C minor. During the first movement, which is 15 minutes long, the recording ever so slowly went flat. The pitch crept downward at 2 cents a minute, ending a full 33 cents flat from the original. The remaining half-hour of the symphony was played in the new, flattened key. When asked, none of the subjects noticed said they noticed a difference in pitch.

Then subjects completed the pitch quiz a second time. Now, pitches that were flat sounded in-tune, and pitches that were in tune sounded a little out of tune. (The subjects still correctly identified sharp pitches.)

In a second experiment, instead of Brahms subjects heard a series of modern musical compositions that only include 5 pitches. Just as before, the music slowly drifted flat and then stayed that way. In the pitch quiz afterward, subjects misjudged all the flat and in-tune notes they heard—not only the five notes they'd listened to.

A brief time listening to out-of-tune notes was able to skew a person's whole internal scale. Yet when subjects heard test pitches played by an instrument they hadn't listened to during the experiment—for example, a set of piano notes after the Brahms symphony, which didn't include a piano—their judgements were correct again. It is "as if each instrument voice retains its own tuning," Hedger and his coauthors write in Psychological Science.

People with absolute pitch, those superpowered few, are thought to learn their pitches in childhood. The pitches aren't absolutely stable, though: the detuning study shows they can be bent and changed by music a person has recently heard.

In a video, senior study author Howard Nusbaum says that the group is now looking for ways to improve people's sense of pitch, rather than detuning it, by taking advantage of this flexibility. "We are constantly changing to meet the circumstances around us," he says. That means someday the rest of us may be a little more perfect.


Image: by Timothy Valentine (via Flickr)

Hedger, S., Heald, S., & Nusbaum, H. (2013). Absolute Pitch May Not Be So Absolute Psychological Science DOI: 10.1177/0956797612473310

Baseball Players Make Worse and Worse Decisions as the Season Goes On

If their goal were to frustrate fans, they couldn't plan it any better. Major-league baseball players reach a low point in their decision making in September, just in time for playoffs. Across all teams, batters swing at more and more pitches they shouldn't as the season goes on.

They may just need a nap.

"Consistently getting too little sleep—even if it's just [by] one hour a night—can lead to a state of chronic sleep deprivation that can compromise performance," says Vanderbilt University neurologist Scott Kutscher. "Specifically, things like judgment and reaction time."

Judgment and reaction time are just what a baseball player needs when a ball is hurtling toward his body at 90 miles an hour: he has to decide whether to swing, then react quickly enough to actually get it done. And sleep deprivation is familiar to pro ball players, who have a packed schedule and frequently travel back and forth across the country.

To see whether baseball players suffer the effects of sleep loss as the season drags on (or skips along for six non-tedious months, depending on your inclinations), Kutscher and his colleagues looked at data from 2011 back to 2006, after the MLB cracked down on steroid use. For each team, they tracked how often players swung at pitches outside the strike zone.

Over the course of the season, the researchers saw a steady increase in how many out-of-the-strike-zone pitches players swung at. These badly judged swings went up by about six-tenths of a percent each month.

Then Kutscher and his colleagues tested that model on the data from the 2012 season. When the numbers from all the MLB teams were pooled together, the model was a tight fit. Out of 30 teams, 24 were swinging at more balls in September than in April. Kutscher presented the findings at a recent conference on sleep.

Other factors aside from sleepiness may be at work. Pitchers might be throwing better curveballs as the months pass, for example. But Kutscher says pitchers threw pretty much the same ratio of balls and strikes throughout the season; if they were improving a lot, you'd expect to see them throwing more strikes. (Not to mention that batters, too, are practicing and honing their skills during the season.)

Since the researchers looked at whole teams rather than individuals, it's also possible that a change in the roster during the season—say, the addition of less experienced players who are called up from the minors—has an effect. Kutscher doesn't think this could account for all the deterioration he witnessed, though.

"I am hesitant to argue that fatigue is 100% of the story," Kutscher says. "But we have findings that are consistent with what we know about fatigue and chronic sleep loss."

Pro ball players, and other athletes, might see their performance improve if they could avoid sleep deprivation. So stop shouting at that guy on your screen who just struck out—he needs to go home and get some rest.


Image: Ed Gaillard (via Flickr)

Better IQ Testing for Animals: There's an App for That

It's 2013, and laboratory pigeons are demanding an upgrade. Well, maybe they aren't demanding so much as continuing to do whatever tasks get them their pigeon pellets. Nevertheless, switching from analog to digital testing could mean more rigorous studies, better statistics, and a chance for previously ignored animals to try their paws at cognition research.

One of the classic cognitive tests that psychologists like to give animals involves two or more strings. At the far end of one string, there's a treat. The animal has to figure out that tugging on the near end of this string will gradually bring the reward close enough to eat.

How classic is the string test? In a recent Animal Cognition paper, Edward Wasserman of the University of Iowa and his coauthors list 74 different papers involving this experiment. Animals subjected to string-pulling tasks have includes apes, monkeys, birds, cats, rats, and Asian elephants. The experiments have been limited, though, to animals that can grasp and pull on a string or rope. Another constraint is the time it takes an experimenter to physically set up the strings and refill the food dishes over and over again.

Wasserman and his colleagues used a pigeon focus group to try out a new kind of string test with no string at all. The whole thing took place on a touchscreen, which you can see above. When pigeons pecked at the square on the near end of a "string," the "dish" on the other end moved a little closer. One dish was an empty black box; the other was a photo of pigeon feed. When a pigeon reeled the food dish all the way in, a tasty (non-virtual) pellet dropped out of a dispenser.

The four pigeons in the study quickly got the gist of things, learning to peck the end of the string attached to the food. They started off with simple tasks, in which the strings were short and didn't cross over each other. Then the strings got longer, appeared at various angles, and eventually crossed. These tasks were increasingly challenging to the pigeons. But even for the hardest tasks, the first string they pecked was usually the correct one.

Unlike in a real string test, there was no pulling—no physical weight of food to focus on dragging closer. Still, Wasserman thinks the touchscreen experiment is an accurate substitute for the real thing. In videos like this one, you can see the pigeons bobbing their heads along the strings as they work, seeming to understand the logic of the puzzle. The authors compare the experiment to a game of Angry Birds, which also simulates real physics (albeit with slingshotted cartoon animals).

Also unlike a real string test, the researchers were able to instantly change the length or placement of the strings. They put their pigeons through tens of thousands of trials without much trouble. All of this means better statistical analyses and more reliable results are possible. Using a touchscreen "allows us to conduct experiments with much greater rigor than would otherwise be the case," Wasserman says.

The new method could also let researchers try this kind of testing on any animal that can work a touchscreen, Wasserman says—"even those without dextrous appendages." For example, fish. He also suggests mammals such as dogs, horses, or cows, as well as birds that can't use their claws like hands. One aquarium has already demonstrated that its penguins can play an iPad game. From the aquarium's video, though, it's unclear whether the penguin is truly enjoying the app for cats, or if trying to nab an onscreen mouse is turning it into an Angry Bird.


Wasserman, E., Nagasaka, Y., Castro, L., & Brzykcy, S. (2013). Pigeons learn virtual patterned-string problems in a computerized touch screen environment Animal Cognition DOI: 10.1007/s10071-013-0608-0

Image: Wasserman et al.

How Science Education Changes Your Drawing Style

Take a look at these neurons. Ignore the fact that several of the brain cells look like snowflakes and at least one looks like an avocado. Can you pick out the drawings done by experienced, professional neuroscientists? What about the ones made by undergraduate science students?

Researchers at King's College London gave a simple task to 232 people: "Draw a neuron." (Actually, being British, they said "Please draw a neuron.") Some of the subjects were undergraduates in a neurobiology lecture. A small group were experienced neuroscientists who led their own research labs at the college. And a third, in-between group included graduate students and postdocs.

The researchers saw marked differences in how the three groups drew their brain cells. To confirm what they saw, they also pooled the drawings together and asked a new batch of subjects to sort the drawings into categories. These subjects agreed: the drawings clustered into distinct styles. The results are in the journal Science Education.

Did you pick out the pictures in the top row as examples from undergrads? Student sketches had lots of detail and were often labeled. In fact, they mostly resembled this classic textbook drawing from 1899, which the authors describe as the "archetype" of brain cells.

Sketches made by lab leaders are on the bottom row. These highly experienced scientists were more likely to make abstract or stylized drawings. Instead of imitating a textbook picture, they drew from their own personal understanding of what a neuron is. (Or possibly, for the scientist on the bottom left, what a martini glass is.)

The graduate students and postdocs, whose drawings are in the middle row, seemed to fall somewhere in between. They didn't label their drawings like undergrads did, and they didn't include quite so much detail. Their neurons were more likely to bend, and the nuclei of the cells were often hidden—in other words, the cells looked more like they would under a microscope, rather than on a textbook page. But they weren't quite as simplified and abstracted as the lab leaders'.

Lead author David Hay says that the three drawing styles represent "different cultures." Undergraduate students spit out textbook images; scientists in training draw on their own observations; and more experienced scientists make "highly conceptual" drawings that represent their personal judgment.

This matters because "learning to reproduce the textbook images is NOT learning science," Hay says. Even postdoctoral researchers didn't seem to have internalized the concept as much as the lab leaders had. However, Hay thinks there are ways that experienced scientists can help students gain perspective.

One way might be by physically acting out scientific ideas. After Hay and his coauthors had students try a couple such exercises—for example, walking on different paths through a laboratory to mimic how neurons grow—the students produced drawings that were more creative and less like the textbook.

Hay thinks students need to internalize scientific concepts before they can play around with them and make their own hypotheses. "Scientists do not simply know information," he says; "they put information to work to discover something new." Failing that, they can create formidable Pictionary teams.


HAY, D., WILLIAMS, D., STAHL, D., & WINGATE, R. (2013). Using Drawings of the Brain Cell to Exhibit Expertise in Neuroscience: Exploring the Boundaries of Experimental Culture Science Education, 97 (3), 468-491 DOI: 10.1002/sce.21055

Images: Hay et al.

Even People Without Synesthesia Find Colors in Music

It’s time to stop scoffing at the synesthetes: linking music to colors is totally normal. It’s not really about the notes, though. Researchers say the colors we find in music are actually the colors of the emotions the music makes us feel.

Synesthetes are people whose sensory experiences overlap; they most often link letters or numbers to certain colors. Music-color synesthesia, in which hearing music triggers the colors, is rarer. In fact, when Stephen Palmer and Karen Schloss at the University of California, Berkeley, set out to do a pilot study of music-color synesthetes, they couldn’t find any. So instead they began looking at the connections between music and colors in everybody else.

As part of a larger study called the Berkeley Color Project, Palmer and Schloss included questions about music. Participants saw a grid of colors while listening to 18 brief clips of classical pieces, and chose the colors that were “most consistent” and "least consistent" with each selection.

The researchers suspected that a connection between music and color, if there was one, might be emotional. So they separately asked their 48 subjects how happy, sad, angry, calm, strong, weak, lively and dreary each piece of music was. Subjects answered the same emotional questions about each color. (If you’re the kind of person who hates attributing personality traits to color swatches, you would not have enjoyed this study.)

There were 18 music samples, representing every possible combination of 3 composers (Bach, Mozart, Brahms), 3 tempi (fast, medium, slow), and 2 modes (major or minor). The Andante movement of Bach's Brandenburg concerto in F major, for example, was Bach/major/slow.

What emerged from this sea of lively Mozart and sad burnt-orange was a clear pattern. People linked uptempo and major-key music to colors that were warmer (yellower), lighter, and more vivid. Pieces with a slower tempo or in a minor key provoked the opposite colors: cooler (bluer), darker, and less saturated.

Additionally, music that was both slow and in a major key tended to be greener. And although there wasn’t a difference between Mozart and Bach, Brahms—a Romantic composer who wrote the most recently of the three—leaned more to the slow and minor colors.

To learn whether this consistency was strictly cultural, Palmer and Schloss found a collaborator at the University of Guadalajara who wanted to repeat the experiments with Mexican subjects.

The researcher, Lilia Prada-León, “initially complained that she didn’t want to study classical music because her Mexican participants don’t listen to that music much,” Parker recalls. “She wanted to do it with mariachi bands, which we may still do sometime later.”

Despite Prada-León's hesitation, the results from her Mexican subjects fit snugly with the results from Americans. “The pattern of results for tempo, mode, and composer were remarkably similar,” the authors write.

Also similar were the emotional ratings that Mexican and American subjects gave the musical selections, as well as the colors themselves. The emotions linked to each piece of music matched the emotions linked to that music's colors. This suggests that music itself doesn't make most people think of color. Instead, music triggers emotion—and that emotion is linked to a certain set of colors in the mind. The results are published in PNAS.

Out of the eight emotions in the original list, only four were needed to explain the results: happy, sad, strong and weak. Happier and stronger colors were associated with upbeat, major-key tunes, while weaker and sadder colors were tied to slower, minor-key pieces.

So what does all this tell us about actual synesthesia?

Palmer says his group has now repeated a version of their experiments with real music-color synesthetes (after finally rounding some up). The results looked different. While non-synesthetes chose different colors depending on the tempo of a piece of music—even if it was the same musical line artificially sped up or slowed down—synesthetes didn't.

"My current opinion is that synesthetes’ color experiences arise from direct mappings from sound to color," Palmer says. In their minds, emotions don't act as the middleman. However, "non-synesthetes’ color associations are indirect and do involve emotional mediation."

But when researchers asked synesthetes to choose the colors that were most "emotionally consistent" with the music, rather than the colors they experienced in their minds, the synesthetes picked out the same colors as everyone else. Additionally, when researchers altered melodies just enough to change them from minor to major, synesthetes—like everyone else—"chose happier colors," Palmer says.

There may be some common ground after all between synesthetes and others. The two groups probably won't agree, though, on the color of the mariachi music playing there.

Images: top by tanakawho (via Flickr); bottom Palmer et al.

Palmer, S., Schloss, K., Xu, Z., & Prado-Leon, L. (2013). Music-color associations are mediated by emotion Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1212562110