Chapter 19. Language and Hemispheric Asymmetry
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By JOHN BRANCH Shortly before he died in July, the former N.F.L. quarterback Ken Stabler was rushed away by doctors, desperate to save him, in a Mississippi hospital. His longtime partner followed the scrum to the elevator, holding his hand. She told him that she loved him. Stabler said that he loved her, too. “I turned my head to wipe the tears away,” his partner, Kim Bush, said recently. “And when I looked back, he looked me dead in the eye and said, ‘I’m tired.’ ” They were the last words anyone in Stabler’s family heard him speak. “I knew that was it,” Bush said. “I knew that he had gone the distance. Because Kenny Stabler was never tired.” The day after Stabler died on July 8, a victim of colon cancer at 69, his brain was removed during an autopsy and ferried to scientists in Massachusetts. It weighed 1,318 grams, or just under three pounds. Over several months, it was dissected for clues, as Stabler had wished, to help those left behind understand why his mind seemed to slip so precipitously in his final years. On the neuropathologist’s scale of 1 to 4, Stabler had high Stage 3 chronic traumatic encephalopathy, or C.T.E., the degenerative brain disease believed to be caused by repeated blows to the head, according to researchers at Boston University. The relationship between blows to the head and brain degeneration is still poorly understood, and some experts caution that other factors, like unrelated mood problems or dementia, might contribute to symptoms experienced by those later found to have had C.T.E. Stabler, well known by his nickname, the Snake (“He’d run 200 yards to score from 20 yards out,” Stabler’s junior high school coach told Sports Illustrated in 1977), is one of the highest-profile football players to have had C.T.E. The list, now well over 100 names long, includes at least seven members of the Pro Football Hall of Fame, including Junior Seau, Mike Webster and Frank Gifford. © 2016 The New York Times Company
Keyword: Brain Injury/Concussion
Link ID: 21861 - Posted: 02.04.2016
By Katy Waldman On May 10, 1915, renowned poet-cum-cranky-recluse Robert Frost gave a lecture to a group of schoolboys in Cambridge, Massachusetts. “Sounds in the mouths of men,” he told his audience, “I have found to be the basis of all effective expression.” Frost spent his career courting “the imagining ear”—that faculty of the reader that assigns to each sentence a melodic shape, one captured from life and tailored to a specific emotion. In letters and interviews, he’d use the example of “two people who are talking on the other side of a closed door, whose voices can be heard but whose words cannot be distinguished. Even though the words do not carry, the sound of them does, and the listener can catch the meaning of the conversation. This is because every meaning has a particular sound-posture.” Frost’s preoccupation with the music of speech—with what we might call “tone of voice,” or the rise and fall of vocal pitch, intensity, and duration—has become a scientific field. Frost once wrote his friend John Freeman that this quality “is the unbroken flow on which [the semantic meanings of words] are carried along like sticks and leaves and flowers.” Neuroimaging bears him out, revealing that our brains process speech tempo, intonation, and dynamics more quickly than they do linguistic content. (Which shouldn’t come as a huge surprise: We vocalized at each other for millions of years before inventing symbolic language.) Psychologists distinguish between the verbal channel—which uses word definitions to deliver meaning—and the vocal channel—which conveys emotion through subtle aural cues. The embedding of feelings in speech is called “emotional prosody,” and it’s no accident that the term prosody (“patterns of rhythm or sound”) originally belonged to poetry, which seeks multiple avenues of communication, direct and indirect. Frost believed that you could reverse-engineer vocal tones into written language, ordering words in ways that stimulated the imagining ear to hear precise slants of pitch. He went so far as to propose that sentences are “a notation for indicating tones of voice,” which “fly round” like “living things.”
By SINDYA N. BHANOO Male zebra finches learn their courtship songs from their fathers. Now, a new study details the precise changes in brain circuitry that occur during that process. As a young male listens to his father’s song, networks of brain cells are activated that the younger bird will use later to sing the song himself, researchers have found. As the learning process occurs, inhibitory cells suppress further activity in the area and help sculpt the song into a permanent memory. “These inhibitory cells are really smart — once you’ve gotten a part of the song down, the area gets locked,” said Michael Long, a neuroscientist at NYU Langone Medical Center and an author of the new study, which appears in the journal Science. Zebra finches learn their courtship song from their fathers and reach sexual maturity in about 100 days. At this point, they ignore their fathers’ tutoring altogether, Dr. Long said. In their study, he and his colleagues played recorded courtship songs to young and old birds and monitored neural activity in their brains. In sexually mature birds, the courtship song did not elicit any neural response. Understanding the role of the inhibitory cells in the brain could help researchers develop ways to manipulate this network, Dr. Long said. “Maybe we could teach old birds new tricks,” he said. “And extrapolating widely, maybe we could even do this in mammals, maybe even humans, and enrich learning.” © 2016 The New York Times Company
By Emily Underwood The boisterous songs a male zebra finch sings to his mate might not sound all that melodious to humans—some have compared them to squeaky dog toys—but the courtship tunes are stunningly complex, with thousands of variations. Now, a new study helps explain how the birds master such an impressive repertoire. As they learn from a tutor, usually their father, their brains tune out phrases they’ve already studied, allowing them to focus on unfamiliar sections bit by bit. The mechanism could help explain how other animals, including humans, learn complex skills, scientists say. The study is a “technical tour de force,” and “an important advance in our understanding of mechanisms of vocal learning and of motor learning generally,” says Erich Jarvis, a neuroscientist at Duke University in Durham, North Carolina. Many species—including humans, chimpanzees, crows, dolphins, and even octopuses—learn complex behaviors by imitating their peers and parents, but little is known about how that process works on a neuronal level. In the case of zebra finches, young males spend the whole of their teenage lives trying to copy their fathers, says Michael Long, a neuroscientist at New York University in New York City. It comes out “all wrong” at first, but after practicing hundreds of times, the birds “sound a lot like dad.” In the new study, Long’s graduate student Daniela Vallentin used a tiny electrode implant to record the activity of neurons in a region of the finch brain called the HVC, which is essential for birdsong learning and production. Weighing less than a penny, the implant can be affixed to a bird’s head and record activity in the brains of freely moving and singing birds, Long says. The researchers also used a powerful light microscope to visualize the activity of individual neurons as the birds listened to a fake “tutor” bird that taught young finches only one “syllable” of a song at a time. © 2016 American Association for the Advancement of Science.
Maggie Koerth-Baker In 1990, when James Danckert was 18, his older brother Paul crashed his car into a tree. He was pulled from the wreckage with multiple injuries, including head trauma. The recovery proved difficult. Paul had been a drummer, but even after a broken wrist had healed, drumming no longer made him happy. Over and over, Danckert remembers, Paul complained bitterly that he was just — bored. “There was no hint of apathy about it at all,” says Danckert. “It was deeply frustrating and unsatisfying for him to be deeply bored by things he used to love.” A few years later, when Danckert was training to become a clinical neuropsychologist, he found himself working with about 20 young men who had also suffered traumatic brain injury. Thinking of his brother, he asked them whether they, too, got bored more easily than they had before. “And every single one of them,” he says, “said yes.” Those experiences helped to launch Danckert on his current research path. Now a cognitive neuroscientist at the University of Waterloo in Canada, he is one of a small but growing number of investigators engaged in a serious scientific study of boredom. There is no universally accepted definition of boredom. But whatever it is, researchers argue, it is not simply another name for depression or apathy. It seems to be a specific mental state that people find unpleasant — a lack of stimulation that leaves them craving relief, with a host of behavioural, medical and social consequences. © 2016 Nature Publishing Group
By Virginia Morell When you hear a bird warbling, you probably think the crooner is a male. And chances are if you’re in the Northern Hemisphere, you would be right. But females also evolved to sing, and many still do—although generally less than the males. One reason may be that it’s more dangerous for them to sing especially when nesting, scientists report today. At least, that’s the case for female fairywrens, the most vocal of which are the most likely to have their eggs and chicks eaten. The study “provides some of the first field evidence indicating why females of so many songbird species might have lost song,” says Karan Odom, a Ph.D. candidate at the University of Maryland, Baltimore, and the lead author of a 2014 study on the evolution of birdsong. Female superb fairywrens (Malarus cyaneus)—a small Australian species—aren’t the only female songbirds that sing. In fact, females sing in 71% of songbird species, often for territorial defense. In species like the superb fairywren, some females even sing when they’re on their nests, a place where, at least theoretically, they should pipe down so as not to attract predators. Rodents, birds, cats, and foxes have all been seen preying on the fairywrens’ nests. “People had observed [this singing in the nest behavior], but they hadn’t investigated it,” says Sonia Kleindorfer, a behavioral ecologist at Flinders University in Adelaide, Australia. “It struck me as odd, and very risky.” © 2016 American Association for the Advancement of Science
By Tania Rabesandratana Here’s one trick to make yourself feel happier: Listen to your own voice—digitally manipulated to make it sound cheery. That’s one potential application of a new study, in which researchers modified the speech of volunteers as they read a short story by Japanese writer Haruki Murakami. The team then altered the voice’s pitch, among other features, to make it sound happy, sad, or fearful. (Compare this normal voice with the same voice modified to sound afraid.) Listening to their own modified voices in real time through a headset, only 16 of 109 participants detected some kind of manipulation. The rest took the voice’s emotion as their own, feeling sad or happy themselves. (The result was less clear for fear.) The researchers suggest that emotions expressed through our voices are part of an ancient, unconscious primate communication system, whereas we have more conscious control over the words we utter. The voice manipulation software is available online, so anyone can experiment with it. The scientists speculate that emotion manipulation could help treat psychiatric disorders like depression. It could also change the mood of online meetings or gaming, they say, or even lend more emotional impact to singing performances. © 2016 American Association for the Advancement of Science
AUDIE CORNISH, HOST: It's unusual for an NFL player - a current player - to criticize the league, especially its handling of controversial issues like concussions or domestic violence, but author Johnny Anonymous has done just that. He's an offensive lineman who's written a book under that pseudonym. It's called "NFL Confidential." In it, he details his 2014 season, including training camp and his big break after a starting player gets injured. He's worried about being fired, so we've masked his voice. First, Johnny Anonymous says getting hurt is always on the mind of the player. ANONYMOUS: It's absolutely constant. The NFL's the only league, the only job you'll find in the world where we have a 100 percent injury rate. CORNISH: So walk us through the questions that come to mind for a player when they first hear that, you know, sickening sound and they're lying there on the field. What are you thinking? ANONYMOUS: For some guys, it's fear, which is why you'll see them kicking and screaming and crying, and some guys it's shock. I know for most of us - and probably all of us - the first thing you think is, I'm done; that's it. You think the injury's going to take the game away from you. CORNISH: So in a way, you know, this is how it happens, right, this discussion of, like, why do people take all the painkillers, you know, like, why do people defy doctors? ANONYMOUS: You have to. It's the only way you make it through. I can tell you right now, honestly, that if I am playing a game, I cannot complete that game without painkillers. I will not be an effective player. © 2016 npr
Keyword: Brain Injury/Concussion
Link ID: 21766 - Posted: 01.09.2016
By Josh Izaac Helmets can reduce the risk of traumatic brain injury by almost 20%. But what if we take so many risks when wearing them that we lose the protective edge they provide? This could be the case, according to a study published this week. Researchers observed 80 cyclists under the guise of an “eye-tracking experiment,” pretending to track their eye-motion via a head-mounted camera as the participants inflated a virtual balloon. For some of the participants, the “eye-tracking devices” were mounted on helmets, while others just wore baseball caps, as can be seen in the picture of the equipment above. The further they inflated the balloon without it popping, the higher their reward and their risk-taking score. Participants wearing helmets inflated their balloons on average 30% more than those who wore caps, the team reports in Psychological Science. The finding could affect how we approach safety design and training, the authors say, as increased risk-taking behavior when using safety equipment might counteract the perceived benefit of the equipment. But what causes this effect in the first place? The underlying mechanism might be related to the concept of “social priming,” where people’s actions towards others are altered subconsciously due to exposure to particular words, cues, objects, or symbols. Importantly, this is the first time social priming has been shown to change people’s behaviour even when they are not interacting with others, providing potential new insights into human behavior. So, next time you’re out riding with a helmet, think twice before attempting that wheelie. © 2016 American Association for the Advancement of Science
Keyword: Brain Injury/Concussion
Link ID: 21765 - Posted: 01.09.2016
Bruce Bower Youngsters befuddled by printed squiggles on the pages of a storybook nonetheless understand that a written word, unlike a drawing, stands for a specific spoken word, say psychologist Rebecca Treiman of Washington University in St. Louis and her colleagues. Children as young as 3 can be tested for a budding understanding of writing’s symbolic meaning, the researchers conclude January 6 in Child Development. “Our results show that young children have surprisingly advanced knowledge about the fundamental properties of writing,” Treiman says. “This knowledge isn’t explicitly taught to children but probably gained through early exposure to print from sources such as books and computers.” Researchers and theorists have previously proposed that children who cannot yet read don’t realize that a written word corresponds to a particular spoken word. Studies have found, for instance, that nonliterate 3- to 5-year-olds often assign different meanings to the same word, such as girl, depending on whether that word appears under a picture of a girl or a cup. Treiman’s investigation “is the first to show that kids as young as 3 have the insight that print stands for something beyond what’s scripted on the page,” says psychologist Kathy Hirsh-Pasek of Temple University in Philadelphia. Preschoolers who are regularly read to have an advantage in learning that written words have specific meanings, suspects psychologist Roberta Golinkoff of the University of Delaware in Newark. © Society for Science & the Public 2000 - 2015.
A 25-year-old former college football player showed signs of a type of brain degeneration from repeated trauma, say researchers who described the autopsy-confirmed case. Chronic traumatic encephalopathy (CTE) is a neurodegenerative disorder associated with repetitive head impacts. Symptoms may include memory loss, impaired judgment, depression and progressive dementia. CTE can only be diagnosed after death by examining the brain. Monday's issue of JAMA Neurology includes a letter describing CTE in a 25-year-old man born with a heart valve disorder. He died of cardiac arrest secondary to a heart infection after playing football for 16 years and experiencing an estimated more than 10 concussions while playing. Dr. Ann McKee and Dr. Jesse Mez of Boston University School of Medicine ran neuropsychological tests on the man when he showed symptoms a year before his death, and then conducted an autopsy, reviewed his medical records and interviewed family members. "Focal lesions of CTE have been found in athletes as young as 17 years; however, widespread CTE pathology, as found in this case, is unusual in such a young football player," they wrote. To their knowledge, it's the first such case to include neuropsychological testing to document the type of cognitive issues with CTE. In this case, the athlete started playing football when he was six, including three years of college football as a defensive linebacker. His first concussion occurred at age eight. ©2015 CBC/Radio-Canada.
Keyword: Brain Injury/Concussion
Link ID: 21750 - Posted: 01.05.2016
By KEN BELSON When St. Louis Rams quarterback Case Keenum sustained a concussion in a game in Baltimore last month, commentators focused on how he wobbled as he got up and questioned why he was not taken out of the game. Few mentioned that he had slammed his head on the turf. In the rush to reduce head trauma in sports, doctors, researchers, leagues and equipment makers have looked at everything from improving helmets to teaching safer tackling techniques. But one little-explored cause of concussions is the field beneath the feet of the millions of athletes who play football, lacrosse, soccer and other sports. A new report compiled by the Concussion Legacy Foundation called attention to the link between head injuries and poorly maintained fields, especially the growing number of those made of synthetic turf. The foundation urged groundskeepers, athletic directors and sports associations to treat their fields as seriously as other protective sports equipment. “We have no national conversation on the technology underneath an athlete’s feet,” the authors wrote in their report, the Role of Synthetic Turf in Concussion. “Helmet technology is an area of great attention and investment, and surfaces deserve the same attention.” The report, which is based on more than a dozen academic studies, cites research that shows that 15.5 percent of concussions in high school sports occur when players hit their head on a playing surface. Another study found that 10 percent of concussions sustained by high school and college football players came after players hit their head on a field. In the N.F.L., about one in seven concussions occurs when a player’s head strikes a synthetic or grass field. © 2015 The New York Times Company
Keyword: Brain Injury/Concussion
Link ID: 21737 - Posted: 12.30.2015
by Sarah Zielinski When you get a phone call or a text from a friend or acquaintance, how fast you respond — or whether you even bother to pick up your phone — often depends on the quality of the relationship you have with that person. If it’s your best friend or mom, you probably pick up right away. If it’s that annoying coworker contacting you on Sunday morning, you might ignore it. Ring-tailed lemurs, it seems, are even pickier in who they choose to respond to. They only respond to calls from close buddies, a new study finds. These aren’t phone calls but contact calls. Ring-tailed lemurs live in female-dominated groups of 11 to 16, and up to 25, animals, and when the group is on the move, it’s common for one member to yell out a “meow!” and for other members to “meow!” back. A lemur may also make the call if it gets lost. The calls serve to keep the group together. The main way ring-tailed lemurs (and many other primates) build friendships, though, is through grooming. Grooming helps maintain health and hygiene and, more importantly, bonds between members. It’s a time-consuming endeavor, and animals have to be picky about who they bother to groom. Ipek Kulahci and colleagues at Princeton University wanted to see if there was a link between relationships built through grooming and vocal exchanges among ring-tailed lemurs. Contact calls don’t require nearly as much time or effort as grooming sessions, so it is possible that animals could be less discriminating when they respond to calls. But, the researchers reasoned, if the vocalizations were a way of maintaining the relationships built through painstaking grooming sessions, then the lemurs would be as picky in their responses as in their grooming partners. © Society for Science & the Public 2000 - 2015.
By KEN BELSON Researchers at several universities and research institutes were awarded almost $16 million Tuesday to find a way to diagnose, while victims are alive, chronic traumatic encephalopathy, a degenerative brain disease linked to repeated head hits in contact sports. The National Institutes of Health and the National Institute of Neurological Disorders and Stroke issued the seven-year grant as part of a long-term study of brain disease in former N.F.L. and college football players, many of whom sustained multiple concussions on the field. Despite the implications that the research may have on football players and the N.F.L., no league money will be used to help pay for the grant. For years, researchers have been able to diagnose C.T.E. only by examining the brains of players who died and whose families agreed to donate the organ, a limitation that has slowed efforts to determine who is susceptible to having the disease. The new study, considered among the most ambitious in the field of sports-related brain injury, aims to develop ways to spot the disease in the living and figure out why certain players get it and others do not. A more comprehensive understanding of the disease, the researchers said, may lead to ways to prevent it. “There are so many critical unanswered questions about C.T.E.,” Dr. Robert Stern, the lead principal investigator and a professor at Boston University School of Medicine, said in a statement. “We are optimistic that this project will lead to many of these answers, by developing accurate methods of detecting and diagnosing C.T.E. during life, and by examining genetic and other risk factors for this disease.” © 2015 The New York Times Company
Keyword: Brain Injury/Concussion
Link ID: 21723 - Posted: 12.24.2015
Scientists hunting for a drug that speeds stroke recovery might find one in the bedside cabinets of millions of Americans. Mice treated with small doses of the sleeping pill Ambien recovered more quickly from strokes than those given a placebo. Ambien is the best-known incarnation of the drug zolpidem, which was prescribed 40 million times in the US in 2011. The researchers say that the finding should be replicated by other labs before proceeding with clinical trials, but it’s an intriguing result for a problem in desperate need of solutions. Strokes cut off the blood supply to part of the brain, leading to the death of oxygen-starved tissue. Some tissue repair can take place in the months afterwards, but most people never fully recover. Although physical therapy can help, there are no drugs that increase the amount of brain tissue repaired. “There are various natural mechanisms that promote a degree of normal recovery in animals and people, but it’s limited”, says Gary Steinberg of Stanford University School of Medicine, who was lead author of the study. One such mechanism may be an increase in signalling by the GABA neurotransmitter in parts of the brain that are able to rewire themselves. Because Ambien acts on GABA receptors, Steinberg and his team wondered whether they could use it to hack this mechanism to improve recovery. © Copyright Reed Business Information Ltd.
By C. CLAIBORNE RAY Q. We know that aquatic mammals communicate with one another, but what about fish? A. Fish have long been known to communicate by several silent mechanisms, but more recently researchers have found evidence that some species also use sound. It is well known that fish communicate by gesture and motion, as in the highly regimented synchronized swimming of schools of fish. Some species use electrical pulses as signals, and some use bioluminescence, like that of the firefly. Some kinds of fish also release chemicals that can be sensed by smell or taste. In 2011, a scientist in New Zealand suggested that what might be called fish vocalization has a role, at least in some ocean fish. In the widely publicized work, done for his doctoral thesis at the University of Auckland, Shahriman Ghazali recorded reef fish in the wild and in captivity, and found two dominant vocalizations, the croak and the purr, in choruses that lasted up to three hours, as well as a previously undescribed popping sound. The sounds of one species recorded in captivity — the bigeye, or Pempheris adspersa — carried 100 feet or more, and the researcher suggested it could be used to keep a group of fish together during nocturnal foraging. Another species, the bluefin gurnard, or Chelidonichthys kumu, was also very noisy, he found. “Vocalization” is a bit of a misnomer, as the sounds these fish make are produced by contracting and vibrating the swim bladder, not by using the mouth. © 2015 The New York Times Company
By SINDYA N. BHANOO Moderate levels of exercise may increase the brain’s flexibility and improve learning, a new study suggests. The visual cortex, the part of the brain that processes visual information, loses the ability to “rewire” itself with age, making it more difficult for adults to recover from injuries and illness, said Claudia Lunghi, a neuroscientist at the University of Pisa and one of the study’s authors. In a study in the journal Current Biology, she and her colleagues asked 20 adults to watch a movie with one eye patched while relaxing in a chair. Later, the participants exercised on a stationary bike for 10-minute intervals while watching a movie. When one eye is patched, the visual cortex compensates for the limited input by increasing its activity level. Dr. Lunghi and her colleagues tested the imbalance in strength between the participants’ eyes after the movie — a measure of changeability in the visual cortex. © 2015 The New York Times Company
Link ID: 21681 - Posted: 12.08.2015
Helen Thompson Just after dawn, barbershop quartets of male howler monkeys echo over the canopy of Mexico’s forests. Jake Dunn remembers them well from his early fieldwork in Veracruz. “Most people who don’t know what they’re listening to assume it’s a jaguar,” says Dunn, a primatologist at the University of Cambridge. The calls serve as a warning to male competitors and an alluring pickup line for females. While studying primates in Mexico, Dunn heard drastic differences between resident howler monkeys. He and his colleagues decided to pin down the origin and evolution of this well-known variation among species. After reading a 1949 paper that classified howlers based on a vocal tract bone called the hyoid, Dunn paired up with Lauren Halenar of the American Museum of Natural History in New York City, who was studying the hyoid’s role in howler biology. Scouring collections at museums and zoos in the United States and Europe, the team used laser scanners to create 3-D models of hyoids from nine howler species. The work required a lot of digging through cupboards for skeletons. “Some of these specimens are hundreds of years old,” says Dunn, who recalls imagining “the early naturalists hunting these animals and bringing back the collections.” Real pay dirt came from the National Museums of Scotland, which had preserved the remains of two howlers that had died of natural causes in zoos. CT and MRI scans of the two specimens provided a rare peek at the howler vocal system’s layout. © Society for Science & the Public 2000 - 2015.
By Karen Russell In late October, when the Apple TV was relaunched, Bandit’s Shark Showdown was among the first apps designed for the platform. The game stars a young dolphin with anime-huge eyes, who battles hammerhead sharks with bolts of ruby light. There is a thrilling realism to the undulance of the sea: each movement a player makes in its midnight-blue canyons unleashes a web of fluming consequences. Bandit’s tail is whiplash-fast, and the sharks’ shadows glide smoothly over rocks. Every shark, fish, and dolphin is rigged with an invisible skeleton, their cartoonish looks belied by the programming that drives them—coding deeply informed by the neurobiology of action. The game’s design seems suspiciously sophisticated when compared with that of apps like Candy Crush Soda Saga and Dude Perfect 2. Bandit’s Shark Showdown’s creators, Omar Ahmad, Kat McNally, and Promit Roy, work for the Johns Hopkins School of Medicine, and made the game in conjunction with a neuroscientist and neurologist, John Krakauer, who is trying to radically change the way we approach stroke rehabilitation. Ahmad told me that their group has two ambitions: to create a successful commercial game and to build “artistic technologies to help heal John’s patients.” A sister version of the game is currently being played by stroke patients with impaired arms. Using a robotic sling, patients learn to sync the movements of their arms to the leaping, diving dolphin; that motoric empathy, Krakauer hopes, will keep patients engaged in the immersive world of the game for hours, contracting their real muscles to move the virtual dolphin.
Angus Chen English bursts with consonants. We have words that string one after another, like angst, diphthong and catchphrase. But other languages keep more vowels and open sounds. And that variability might be because they evolved in different habitats. Consonant-heavy syllables don't carry very well in places like windy mountain ranges or dense rainforests, researchers say. "If you have a lot of tree cover, for example, [sound] will reflect off the surface of leaves and trunks. That will break up the coherence of the transmitted sound," says Ian Maddieson, a linguist at the University of New Mexico. That can be a real problem for complicated consonant-rich sounds like "spl" in "splice" because of the series of high-frequency noises. In this case, there's a hiss, a sudden stop and then a pop. Where a simple, steady vowel sound like "e" or "a" can cut through thick foliage or the cacophony of wildlife, these consonant-heavy sounds tend to get scrambled. Hot climates might wreck a word's coherence as well, since sunny days create pockets of warm air that can punch into a sound wave. "You disrupt the way it was originally produced, and it becomes much harder to recognize what sound it was," Maddieson says. "In a more open, temperate landscape, prairies in the Midwest of the United States [or in Georgia] for example, you wouldn't have that. So the sound would be transmitted with fewer modifications." © 2015 npr