Links for Keyword: Laterality

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By John Roach Lefties were as outnumbered 600,000 years ago as they are today, according to telltale markings on teeth found on Neanderthal and Neanderthal ancestors in Europe. The finding serves as a new technique to determine whether a person was left- or right-handed from limited skeletal remains, and it also suggests that a key piece for the origin of language was in place at least half a million years ago, David Frayer, an anthropologist at the University of Kansas, told me today. But while ancient righties appeared to outnumber lefties nine to one, the findings don't reveal whether some of the ancient lefties dominated in sports, as baseball players do today; and in politics, where being left-handed seems to help open the door to the White House. The telltale tooth markings, based on experiments, appear to result from how these Neanderthals and their relatives processed hides with stone tools, explained Frayer, a co-author of a paper on the findings published this month in the journal Laterality. One of his colleagues in Spain had people wear a mouth guard and then strike a hide as if they were cutting or stretching it with a stone tool. Every now and then, the test subjects were asked to whack their guarded teeth, as the researchers think would have accidentally happened as the ancient humans worked away.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 15251 - Posted: 04.21.2011

By PERRI KLASS, M.D. Humans are asymmetric animals. Early in our embryonic development, organs turn to one side or the other — heart to the left, liver to the right and so on. In rare cases, an organ may turn up on the “wrong” side with no untoward effects. (I once examined a child with dextrocardia, or heart on the right.) But there is one form of asymmetry that is common and, until quite recently, stigmatized: handedness. Over the centuries, left-handers have been accused of criminality and dealings with the devil, and children have been subjected to “re-education.” In recent years the stigma has largely vanished; among other things, four of our last five presidents — Reagan, the elder Bush, Clinton, Obama — have been left-handed. (Reagan is sometimes cited as ambidextrous.) But the riddle of why about 10 percent of children are born with this essentially human asymmetry remains. “This is really still mysterious,” said Clyde Francks, the lead author of a 2007 study in which Oxford University researchers identified a genetic variant linked to left-handedness. Hand asymmetry (whether left or right) is related to brain asymmetry. And that, Dr. Francks said, “is not at all understood; we’re really at the very beginning of understanding what makes the brain asymmetrical and what goes wrong — we don’t understand that process in the normal case.” © 2011 The New York Times Company

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 15076 - Posted: 03.07.2011

by Ferris Jabr People who are relatively ambivalent about which hand they use may also have moods that are more susceptible to suggestion. So says Ruth Propper at Montclair State University, New Jersey, and colleagues, who discovered that "inconsistent-handers" – those who favour neither their right nor left hand – are more easily persuaded to feel a certain way than consistent right-handers. Almost 90 per cent of the world's population remains loyal to the right hand, whether brushing their teeth, flipping through TV channels or whipping up some brownies. The remaining 10 per cent is divided between people who consistently prefer the left hand and those who switch between right and left. To see whether handedness had any relationship to emotional stability, Propper attempted to influence the moods of inconsistent-handers and right-handed individuals by asking them think happy, sad or anxious thoughts while listening to different kinds of classical music. Inconstant moods Proper found that inconsistent-handers not only reported that as soon as they walked into the lab they had more negative feelings, suggesting their moods were more immediately influenced by their surroundings, but were also far more likely to report slipping into a new mood during the experiment. The right-handers proved more resistant to suggestion, reporting less flux in emotion. © Copyright Reed Business Information Ltd

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 11: Emotions, Aggression, and Stress
Link ID: 15038 - Posted: 02.22.2011

By Jennifer Viegas When a Southpaw shakes hands, his left eye and the right portion of his brain are working hard to process the other individual, suggests a new study. The research helps to explain why hand and limb preferences exist across numerous species. The predisposition, as it turns out, are tied to ocular dominance, or the tendency to prefer visual input from one eye over the other, according to the study, published in the latest Royal Society Biology Letters. Ocular dominance, in turn, is driven by cerebral lateralization, which refers to how information processing is divided and coordinated between the brain's left and right hemispheres. In recent U.S. history, the majority of presidents have been left-handed (Gerald Ford, Ronald Reagan, George H.W. Bush, William Clinton and Barack Obama), but scientists haven't yet found a link between hand preference and an individual's abilities. "At this stage we have no reason to think that left- or right-brained animals are superior or analyze information differently, except that it's the mirror image," co-author Culum Brown told Discovery News. Brown, director of Advanced Biology at Macquarie University, and colleague Maria Magat studied the phenomenon in Australian parrots. These birds, like humans, have a tendency to use either their right or left limb more than the other. © 2011 Discovery Communications, LLC. T

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 7: Vision: From Eye to Brain
Link ID: 14951 - Posted: 02.03.2011

by Catherine de Lange GREAT ideas can feel like they come out of nowhere. Now we're a step closer to understanding where they do originate. The thinking is that areas for language and creativity compete in the brain, which might explain why some people with brain damage suddenly become artistic. Originality - or the ability to think up novel ideas that don't occur to many other people - is a key aspect of creativity. But researchers are struggling to pin down where the gift comes from. "We were amazed by the conflicting results in the literature," says Simone Shamay-Tsoory, from the University of Haifa, Israel. To better pinpoint the areas involved in creative thinking, Simone Shamay-Tsoory, and her team compared 40 people with damage to one of three distinct areas in the brain, and a group without any damage. As well as having their brains scanned, the two groups were shown 30 identical circles on a piece of paper and given 5 minutes to draw as many different pictures of meaningful objects as they could, each of which had to include at least one circle (see diagram). The volunteers were scored on their total number of responses and also on the number of statistically rare responses, deduced from earlier experiments on healthy volunteers. The test measures "divergent thinking" - the ability to generate new ideas that give different solutions to a particular problem. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 14: Attention and Consciousness
Link ID: 14797 - Posted: 12.18.2010

Humans are not the only species to prefer to use their right hand -- chimpanzees also share the trait, according to a new study by Spanish scientists. The researchers reached their findings, published in the latest edition of the American Journal of Primatology, after observing 114 chimpanzees from two primate rescue centers, one in Spain and the other in Zambia. The primates were provided with food hidden inside tubes and the scientists monitored them to see which hand they used to get at it, either their fingers or with the help of tools. "The chimpanzees showed a preferential use of the right hand to get the food from the tube," the Catalan Institute of Human Palaeoecology and Social Evolution, which coordinated the study, said in a statement. "This feature had traditionally been considered exclusively human and had been believed to be caused by asymmetries observed in the human brain that are related to the realization of complicated activities that require the use and coordination of both hands." The study also found that female chimpanzees, like their human counterparts, are more likely to be right-handed than males. The researchers said this suggests "that just like in our species, there are shared biological factors, genetic and hormonal, that modulate the functioning of our brain." © 2010 Discovery Communications, LLC

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 14604 - Posted: 10.30.2010

Melissa Dahl writes: You know that saying "the left hand doesn't know what the right is doing"? For people with a strange disorder called alien hand syndrome, that's literally true -- the neuropsychiatric condition makes them feel as if one of their hands has taken on a mind of its own. "An alien hand is an arm and hand that moves when the person to whom that arm belongs does not intend it to move," says Dr. Ken Heilman, a neurologist at the University of Florida College of Medicine in Gainesville, Fla. Heilman goes on to note that there are many neurological conditions that cause an arm to move unintentionally -- like seizures or tremors, and movement disorders such as chorea, dystonia and athetosis. Here's the difference: In each of those cases, if the arm moves, it's pretty much just flailing about purposelessly, "but with an alien hand, the movement appears to be purposeful." Creepy. Heilman recalls one patient whose hands actually fought over fashion: Her right hand took a pair of red shoes out of the closet. Her left hand -- the "alien" hand -- pulled the red shoes out of her right hand, put them back and picked up a pair of blue shoes. When the right hand went again for the red shoes, the left hand slammed the closet door on the right hand. A German neurologist and psychiatrist named Kurt Goldstein was the first to report a case of alien hand syndrome in 1908. His patient's left hand seemed to do whatever it pleased, including, at least once, an attempt to throttle its owner. It's most commonly the result of an injury to an area of the brain called the corpus callosum. © 2010 msnbc.com

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 14: Attention and Consciousness
Link ID: 14603 - Posted: 10.30.2010

WASHINGTON— There really may be something different about the brains of math-heads. Mathematically gifted teens did better than average-ability teens and college students on tests that required the two halves of the brain to cooperate, as reported in the April issue of Neuropsychology, published by the American Psychological Association (APA). In the study, a joint effort of psychologists at the U.S. Army Research Institute for the Behavioral and Social Sciences at Fort Benning, Ga. and the University of Melbourne, Australia, researchers studied 60 right-handed males: 18 mathematically gifted (averaging nearly 14 years in age), 18 of average math ability (averaging just over 13), and 24 college students (averaging about 20). Math giftedness seems to favor boys over girls, appearing an estimated six to 13 times more often. It’s not known why but prenatal exposure to testosterone is suspected to be one influence due to its selective benefit to the right half of the brain. The gifted boys were recruited from a Challenges for Youth-Talented program at Iowa State University. Whereas the average Scholastic Aptitude Test (SAT) math score for college-bound high-school seniors is 500 (out of 800), the mathematically gifted boys’ average SAT math score in middle school was 620. © 2004 American Psychological Association

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 5263 - Posted: 06.24.2010

WASHINGTON— There really may be something different about the brains of math-heads. Mathematically gifted teens did better than average-ability teens and college students on tests that required the two halves of the brain to cooperate, as reported in the April issue of Neuropsychology, published by the American Psychological Association (APA). In the study, a joint effort of psychologists at the U.S. Army Research Institute for the Behavioral and Social Sciences at Fort Benning, Ga. and the University of Melbourne, Australia, researchers studied 60 right-handed males: 18 mathematically gifted (averaging nearly 14 years in age), 18 of average math ability (averaging just over 13), and 24 college students (averaging about 20). Math giftedness seems to favor boys over girls, appearing an estimated six to 13 times more often. It’s not known why but prenatal exposure to testosterone is suspected to be one influence due to its selective benefit to the right half of the brain. The gifted boys were recruited from a Challenges for Youth-Talented program at Iowa State University. Whereas the average Scholastic Aptitude Test (SAT) math score for college-bound high-school seniors is 500 (out of 800), the mathematically gifted boys’ average SAT math score in middle school was 620. © 2004 American Psychological Association

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 5262 - Posted: 06.24.2010

Kerri Smith 'Southpaw', 'goofy', or just plain 'lefty' are some of the many names that left-handers have been called. In certain societies, the aversion can go so far that some left-handers are forced to write with their right hand, regardless of their natural tendencies. Now, a study of such 'converted' left-handers has found that the way their brains are organized, and how hard particular regions work, changes as a result of this switch. Some areas of the brain continue to look like those of a practising lefty, whereas other areas switch to the patterns of a righty, the research reveals. "The question now is, 'do converts suffer because of this extra attention that they exert?'," says Stefan Klöppel of University College London, who led the work. The answer to that is as yet unknown. The hand used to write with is generally controlled by the opposite side of the brain — in right-handed people, movement-related areas on the left side of the brain are more active when they move the fingers of their right hand. But converting from being left-handed to right-handed doesn't simply move brain activity to the other half of the brain, Klöppel and his colleagues found. ©2007 Nature Publishing Group

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 10502 - Posted: 06.24.2010

This column is brought to you care of what the Australians call a "shonky molly-dooker." Not so much a left-hander as a leftish-hander. What I do is write and draw with my left hand but approach everything else the – ha-ha – right way. This anomaly has led me, over the years, to pay more than passing attention to what you might call the science of left-handedness. If it can find a believable explanation for why shonky molly-dookerness should persist in human evolution, maybe an extension of that reasoning will tell me something essential about myself. That's why my eyes opened when I started to read a recent paper published in the journal Brain by Sandra Witelson and her colleagues at McMaster University. They were interested in coming up with an as accurate as possible measure of the relationship of brain size to braininess. They approached people dying of cancer in a Hamilton hospital and asked whether they would take IQ tests. Afterwards, the scientists did an autopsy on the brains to see how volume compared with IQ score. The test group was divided between men and women and right- and left-handers. The handedness was measured because previous evidence has accumulated that there might be relationship between handedness and brain size. © CBC 2006

Related chapters from BP7e: Chapter 1: Biological Psychology: Scope and Outlook; Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 1: An Introduction to Brain and Behavior; Chapter 15: Language and Our Divided Brain
Link ID: 8400 - Posted: 06.24.2010

(Bethesda, MD) – The phrase, “the right hand doesn’t know what the left hand is doing,” has its roots in a passage of the Bible (Matthew 6:3). If there is truth to this old saying, the reasons may have as much to do with the way the brain obtains information from the arms as it does from the observations of ancient scribes. Most individuals are either left- or right-handed. How the skills they have learned from the dominant arm (or hand) are transferred to the non-dominant arm have long intrigued physiologists and neurologists. Copyright © 2003, The American Physiological Society,

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 5: The Sensorimotor System
Link ID: 3577 - Posted: 06.24.2010

by Greg Miller For most people, it's trivially easy to reach for an object with one hand and keep the other hand still. But in people with a rare inherited condition, when the brain orders one hand to move, the other hand performs the same movement at the same time. Now scientists think they've found a gene mutation that's responsible for this "mirror movement" disorder. The find could yield insights into how the brain gets wired during development. The discovery is exciting, says Susan Ackerman, a neurogeneticist at the Jackson Laboratory in Bar Harbor, Maine, who was not involved in the research. The mutation affects a receptor for a signaling molecule called netrin that is involved in one of the best-studied pathways in developmental neuroscience, she says, but all of that work has been done in animals such as mice, worms, and fruit flies. "To my knowledge, this is the first indication that it's really important in humans too." Mirror movements are a rare and puzzling phenomenon. Babies often exhibit mirror movements in which, for example, an intentional grasping movement with one hand or a kick with one leg is accompanied by a similar involuntary movement by the other side. But these anomalies almost never persist into adulthood, says Guy Rouleau, a neurologist at the University of Montreal in Canada. However, Rouleau and colleagues have recently identified two families—one in Iran and one in Canada—in which some individuals exhibit mirror movements as adults. © 2010 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 11: Motor Control and Plasticity; Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 15: Language and Our Divided Brain
Link ID: 14027 - Posted: 06.24.2010

By Bruce Bower CHICAGO — Give the chimpanzees living at Uganda’s Toro-Semliki Wildlife Reserve a hand for having the mental moxie to dig water-collection holes along the edge of a river that flows only during rainy months. In fact, give them two hands, because wells dug by these chimps show no evidence of having been fashioned by either right-handers or left-handers, according to anthropologist Linda Marchant of Miami University in Oxford, Ohio. Evidence of ambidexterity in Semliki chimps counters a suggestion from other researchers, based largely on studies of captive animals, that chimps often favor one hand over the other when performing various tasks. If it exists, chimp handedness interests researchers because it may reflect an evolutionary move toward a brain organized more like that of people — with one hemisphere dominating over the other and prompting either right- or left-handedness —than has often been assumed. “We see no signs of handedness among the Semliki chimps, which appears to be the condition in the wild,” said anthropologist and study coauthor William McGrew of the University of Cambridge in England. Marchant presented her team’s new findings on April 3 at the American Association of Physical Anthropologists annual meeting. Rather than excluding hand preferences altogether among wild chimps, findings at Semliki indicate that chimps use both hands equally on physically demanding jobs, such as well digging, remarked Elizabeth Lonsdorf, director of the Lester E. Fisher Center for the Study and Conservation of Apes at Lincoln Park Zoo in Chicago. © Society for Science & the Public 2000 - 2009

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 12728 - Posted: 06.24.2010

By ANAHAD O’CONNOR Already burdened with the minor mishaps that arise from living in a world designed for righties, their lot in life seemed to worsen considerably in the 1980s, when a study argued that southpaws had several times the risk of chronic headaches — and immune disorders — as their right-handed counterparts. The reason, it was theorized, had something to do with variations in fetal brain development, though no precise explanation was given. But a raft of evidence now suggests that the migraine finding, though intriguing, was less fact than statistical artifact. A more extensive study published in March by German scientists examined a group of 100 patients who had received a diagnosis of migraine based on standards set by the International Headache Society. After finding no evidence of a link between handedness and migraines, the scientists pooled data from five other studies and conducted a meta-analysis. Still, there was no evidence of a relationship — a conclusion echoed by many similar studies. Several studies have also examined whether there is any relationship between left-handedness and increased risk of immune disorders. The findings are inconclusive. Proponents argue that fetal exposure to high levels of testosterone could be responsible, and they point out that left-handedness is more common in men than women. Critics say more research is needed. THE BOTTOM LINE Most studies have found that being left-handed does not increase the risk of migraines. Copyright 2008 The New York Times Company

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 5: The Sensorimotor System
Link ID: 11526 - Posted: 06.24.2010

Bruce Bower The concept of identity theft assumes an entirely new meaning for people with brain injuries that rob them of their sense of self—the unspoken certainty that one exists as a person in a flesh—bounded body with a unique set of life experiences and relationships. Consider the man who, after sustaining serious brain damage, insisted that his parents, siblings, and friends had been replaced by look-alikes whom he had never met. Everyone close to him had become a familiar-looking stranger. Another brain-injured patient asserted that his physicians, nurses, and physical therapists were actually his sons, daughters-in-law, and coworkers. He identified himself as an ice skater whom he had seen on a television program. The sense of "I" can also go partially awry. After a stroke had left one of her arms paralyzed, a woman reported that the limb was no longer part of her body. She told a physician that she thought of the arm as "my pet rock." Other patients bequeath their physical infirmities to phantom children. For instance, a woman blinded by a brain tumor became convinced that it was her child who was sick and blind, although the woman had no children. Copyright ©2006 Science Service.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 8520 - Posted: 06.24.2010

By Anna Salleh, ABC Science Online — There may be more left-handed people than we realize, an international study has found. If we include the number of people who throw a ball, strike a match or use a pair of scissors with their left hand, the researchers say the world looks more of a left-handed place. Australian researcher Sarah Medland of the Queensland Institute of Medical Research in Brisbane and team publish the research in the current issue of the journal Laterality. Left-handed people face problems in a world where most things, from scissors to can-openers and computers to power tools, are designed for right-handers. In the past left-handers faced even greater problems. Some schoolchildren were forced, under threat of the strap, to write with their right hand, regardless of their natural tendency. Medland and team hoped to shed light on the contribution of cultural factors like this on the distribution of handedness. Copyright © 2004 Discovery Communications Inc.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 6108 - Posted: 06.24.2010

Out of Left Field: Studies of chimpanzees finally give southpaws a fair shake By Jocelyn Selim At the Yerkes Regional Primate Research Center in Atlanta, a large chimpanzee named Winston is taking part in an unusually pleasant experiment. Using his left hand, he reaches over and grabs a length of PVC pipe from primatologist Bill Hopkins, then he uses his right to scoop out some peanut butter smeared inside. "Winston's a righty," Hopkins says, offering another piece of pipe to a smaller chimp hovering nearby. This one grabs the pipe with his right hand and digs out the peanut butter with his left. "That's Winston's younger brother," Hopkins says. Over the past 10 years, Hopkins's research has offered the first definitive proof that apes, like humans, have hand preferences: A third of the Yerkes chimpanzees are lefties and the rest are righties. But Winston and his brother point to an even more intriguing pattern: The younger the sibling, the more likely he or she is to be a lefty. And if handedness is clearly tied to birth order in chimps, it could throw a monkey wrench into theories of handedness in humans as well. Granted, those theories already have a lot of explaining to do. Among humans, lefties are more likely than righties to suffer from dyslexia, schizophrenia, stuttering, and other disorders. But lefties are also more likely to be Mensa members, musicians, and U.S. presidents (Bill Clinton, George Bush Sr., and Ronald Reagan are all left-handed). And al-though left-handedness runs in families—notably in Queen Elizabeth II, Prince Charles, and Prince William—more than two-thirds of all lefties are born to right-handed couples. Even identical twins often have opposite hand preferences. © Copyright 2002 The Walt Disney Company.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 1199 - Posted: 06.24.2010

By Peter F. MacNeilage, Lesley J. Rogers and Giorgio Vallortigara The left hemisphere of the human brain controls language, arguably our greatest mental attribute. It also controls the remarkable dexterity of the human right hand. The right hemisphere is dominant in the control of, among other things, our sense of how objects interrelate in space. Forty years ago the broad scientific consensus held that, in addition to language, right-handedness and the specialization of just one side of the brain for processing spatial relations occur in humans alone. Other animals, it was thought, have no hemispheric specializations of any kind. Those beliefs fit well with the view that people have a special evolutionary status. Biologists and behavioral scientists generally agreed that right-handedness evolved in our hominid ancestors as they learned to build and use tools, about 2.5 million years ago. Right-handedness was also thought to underlie speech. Perhaps, as the story went, the left hemisphere simply added sign language to its repertoire of skilled manual actions and then converted it to speech. Or perhaps the left brain’s capacity for controlling manual action extended to controlling the vocal apparatus for speech. In either case, speech and language evolved from a relatively recent manual talent for toolmaking. The right hemisphere, meanwhile, was thought to have evolved by default into a center for processing spatial relations, after the left hemisphere became specialized for handedness. In the past few decades, however, studies of many other animals have shown that their two brain hemispheres also have distinctive roles. Despite those findings, prevailing wisdom continues to hold that people are different. Many investigators still think the recently discovered specializations of the two brain hemispheres in nonhumans are unrelated to the human ones; the hemispheric specializations of humans began with humans. © 1996-2009 Scientific American Inc.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 12982 - Posted: 06.24.2010

By C. CLAIBORNE RAY Q. Is left-handedness less common in women? A. Studies of Western populations usually find that left-handedness is somewhat less common in women, but perhaps because left-handedness is hard to define, the difference varies by several percentage points. One large study in 1971 used a standard called the Edinburgh Handedness Inventory, which asks which hand is used for different tasks, and found that 90 percent of women were right-handed, as against 86 percent of men. But a smaller 1988 study using the same inventory found no significant difference by sex, and a large Internet study done for the BBC for another purpose found sex differences that varied by ethnic group. Anthropologists’ studies of traditional cultures in Africa and elsewhere found a wide range of differences, from no left-handed women at all to levels approximating those in Western studies. Some researchers have suggested that the trend for more men to be left-handed is not universal or may be affected by social norms, with left-handed men stubbornly clinging to left-handedness while left-handed women are more easily persuaded to join the majority. Copyright 2006 The New York Times Company

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 8: Hormones and Sex
Link ID: 9175 - Posted: 06.24.2010