HAND SKILL, RELATIVE; HSR

Alternative titles; symbols

HANDEDNESS
Gene map locus 2p12-q22

TEXT

Annett (1964) postulated that right-handedness is an incomplete dominant, or intermediate, i.e., that dominant homozygotes are always right-handed with 'speech highly developed in the left hemisphere.' Recessive homozygotes are consistently left-handed with speech in the right hemisphere. Heterozygotes may use either hand and develop speech in either hemisphere. From twin studies, Rife (1940) had earlier concluded that handedness is a multifactorial trait. Levy and Nagylaki (1972) reviewed experimental data and theoretical work on the inheritance of handedness and cerebral dominance. They found that all quantitative information was in excellent agreement with a 2-gene, 4-allele model, one locus pertaining to left or right hemispheric dominance and the other to contralateral or ipsilateral hand control relative to the dominant hemisphere. Hicks and Kinsbourne (1976) found that hand preference of college students correlated significantly with the writing hand of their biologic parents but not with that of the stepparents.

Creation of the Sinister: Biological Contributions to Left-handedness

by Monica Watkins

We live in a right-handed world. Left-handedness has been, and in some cases still is, considered an inconvenience, a bad habit, or a symbol of the "sinister". Studies still attempt to link left-handers with socially undesirable behaviors, such as psychosis or criminal activity. The social implications of these stigmas are immense. "Left-handers may be one of the last unorganized minorities in our society, with no collective power and no real sense of common identity," says Stanley Coren (1992).

Where have all the lefties gone?
Star Tribune, March 4, 1993
Lewis Cope

About 13 percent of Americans are left handed, but only about 5
percent of those in their fifties are left handed. A recent study by
Robert Glynn concluded that left handed people live as long as
right-handers suggesting that the fact that their are fewer left
handers among older people can be accounted for by pressure to
become right handed. The author of earlier studies which claimed
that left handers live less long, Stanley Coren, believes that left
handers have a higher rate of deaths from accidents because tools,
driving customs etc. favor right handers.

The fact that there are a higher proportion of left handers among
younger people and that younger people have a higher proportion
of accidents has allowed both Coren and Glynn to claim that the
other has not answered the question. Coren can claim that Glynn,
by limiting himself to subjects over 65, has taken out the very
group where the danger of being left-handed has an effect. Glynn
can claim that Coren by not controlling for age will necessarily
find a shorter lifetime for left handers just because there are more
left handers among the younger people and younger people have a
higher accident rate.

In general the left and right hemispheres of your brain process information in different ways. We tend to process information using our dominant side. However, the learning and thinking process is enhanced when both side of the brain participate in a balanced manner. This means strengthening your less dominate hemisphere of the brain. Listed below are information processing styles that are characteristically used by your right or left brain hemisphere. Read the information below to help you understand how your brain processes information. Pay attention to your less dominant style so that you can learn how to improve it.

Linear Vs. Holistic Processing
The left side of the brain processes information in a linear manner. It processes from part to whole. It takes pieces, lines them up, and arranges them in a logical order; then it draws

Professor Michael Corballis
University of Auckland

and

Professor Chris McManus
University College of London

GEOFF BURCHFIELD: Can I ask you first off how universal amongst human cultures is the dominance of right handedness?

MICHAEL CORBALLIS: I think its completely universal. I don't know of any group of people anywhere now or through recorded history that's been other than predominantly right handed so about 90 percent right handedness seems to be completely universal in the human population

GEOFF BURCHFIELD: So even with people who write from from right to left and risk smudging the page?

reprinted from the BBC

People who are left-handed are twice as likely as right-handers to suffer from bowel disease, claim scientists. A study of more than 20,000 people in the UK found that the risk of inflammatory bowel disease - usually Crohn's disease or ulcerative colitis - doubled in left-handed people.

Although the prevalence of left-handedness in the general population is around one in ten, 21% of the people found to have inflammatory bowel disease were left-handed.
The research, by a team at the Royal Free Hospital and University College Medical School in London, comes after earlier studies showed left-handers are at increased risk of other conditions such as asthma and diabetes.

reprinted from the BBC

reprinted from the New Scientist

NewScientist.com news service
Will Knight

Left-handed people may be better equipped for close range mortal combat than those who rely on their right hands, according to researchers.

Charlotte Faurie and Michel Raymond of the University of Montpellier in France examined the number of left-handed people in unindustrialised cultures as well as the homicide levels within each culture.

Interviewer - Now Chris, you wrote a book, 'Right Hand, Left Hand', which won you a whole heap of prizes because it's something people are absolutely fascinated by. Why do these left-handers exist?

Chris M - The simple answer is because of genes. Some of us have one set of genes while others of us have another. It's the same reason that some people have blue eyes or blond hair. And therefore, some people just have their brains the other way round. That's the simple answer. The really difficult question to answer is why did that ever happen? Why did we become mostly right handed in the first place and why did others become left handed? That's a good evolutionary story as there have to be advantages to being right handed and advantages to being left handed. They're difficult questions.

reprinted from the Purdue News

August 5, 2003

WEST LAFAYETTE, Ind. – It may be a right-handed world, but recent Purdue University research indicates that the first building blocks of life were lefties – and suggests why, on a molecular level, all living things remain southpaws to this day.

In findings that may shed light on the earliest days of evolutionary history, R. Graham Cooks and a team of Purdue chemists have reported experiments that suggest why all 20 of the amino acids that comprise living things exhibit "left-handed chirality," which refers to the direction these basic biological molecules twist–and how a single amino acid might be the reason.

reprinted from the American Scientist

Handedness is closely tied to the way hair spins on the scalp
Christopher R. Brodie

Is handedness genetic? The question is centuries old and has been the subject of hundreds of scientific papers. Now, the verdict is finally in, and the answer is yes. But there is an unexpected twist to the story: It seems that the same gene that creates lefties also determines which way hair whorls around.

Amar Klar, the head of developmental genetics at the National Cancer Institute campus in Frederick, Maryland, explained the link between handedness and the way hair spins on the scalp in the September 2003 issue of Genetics. It seems a single gene with two alleles controls both traits. The dominant allele dictates right-handedness—and a clockwise hair spiral.

reprinted from CBC Canada

They’ve been vilified throughout history as gauche, sinister and wrong-headed. So what is the truth about lefties? It turns out there is little consensus among scientists about what causes handedness or what it means to be a southpaw. Some researchers believe the trait comes down to genetics. Others propose that environmental factors or brain trauma at birth might be at the root of the behaviour. We spoke to some of the few scientists digging into the causes and effects of being a lefty in a right-handed world:

Dr. Pamela Bryden is a professor of kinesiology at Wilfrid Laurier University in Waterloo. She's found that lefties were definitely more flexible and adaptable when she measured their abilities to perform tasks with their non-dominant hand.

Dr. Amar Klar is a geneticist at the National Cancer Institute in Maryland. Dr. Klar decided to study left-handedness by heading to a shopping mall to study the hair whorls on the tops of shoppers' heads. That study led him to believe that most people inherit a single dominant gene for right-handedness, but without that gene, a person has a 50 per cent chance of being a left-hander.

Dr. Chris McManus is a professor of psychology at University College London and author of Right Hand, Left Hand: The Origins of Asymetry in Brains, Bodies, Atoms and Cultures. He believes there is a gene for right-handedness. But he thinks an evolutionary quirk occurred tens of thousands of years ago that caused a gene mutation, which Dr. McManus calls the "chance gene". It cancels the bias to the right, so those who inherit it have a 50-50-chance of ending up lefties.

Dr. Ira Perelle is a professor in the department of psychology at Mercy College in New York. He believes there are at least three possible causes for left-handedness, including the possibility that at a very young age, a child can learn the behaviour.