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A Hand Test: Genetic, Psychological and Social Analysis of Being Left-Handed

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Topics: Handedness
A Hand Test: Genetical, Psychological and Social Analysis to Being Left-Handed

The preferred usage of one hand over the other is called handedness. Approximately 90 percent of the world’s populations are right-handed and these were passed on from one generation to other, although learning and culture could be the other possibilities to these phenomena (Lexicon University Encyclopedia, 1988). According to the New Encyclopedia Britannica (1993), laterality is the development of specialized functions in each of the hemisphere in our brain or the side of our body it controls. Handedness is the most obvious example of laterality, which uses one hand to perform activities over the other. It can be classified as right-handed, left-handed or ambidextrous. In anatomy, our hands are mirror images. The vast majority of the right-handers use their right hands exclusively for tasks requiring dexterity and mastery (Hockenbury, 1997). This also goes the same for the people who use their left hands or the so-called “left-handers.” Left-handers are the people who use their left hands in writing or most of their usual activities rather than their right hands. One person in ten is a left-hander. Anywhere you look, left-handedness is something of a rarity (de Kay, 1979). Almost ten percent (somewhat more among males, somewhat less among females) of the human population is left-handed. Judging from the cave drawings and the tools of the prehistoric humans, this veer to the right occurred a long way back in the development of our species (Myers, 1986). Men are twice as many as women who were left-handed. They believe that this is due to the fact that males are exposed to higher testosterone levels during pregnancy (Hockenbury, 1997). For most left-handers, living in a right-handed world may sometimes difficult for them. Most tools used in our daily lives are designed primarily for the right-handers. For left-handers, handwriting shows an obstacle. Adapting specifically to right-handed tools for music, business education and physical education should be done and mastered for some left-handers (Lance, 2006).The physical environment we are living today are specifically designed for the right-handers, but this should not be linked to a small percentage of left-handed elderly in our society. Most tools, equipments and machines in school and workplaces are designed for the convenience and safety of the right-handers. And these inconveniences are hazardous to health and safety of the left-handers. This can only be prevented if the machines, tools and equipments are to be made “user-friendly,” meaning ideally suited for both left-handers and right-handers (Kassin, 1989). Researchers hypothesized that a gene in a person’s DNA might confer to his handedness, specifically right-handedness. They theorized that people who lack this gene might display a random handedness, one-half being right-handed and the other half being left-handed. The problem with this theory that the other studies show that there is 30%-40% chance of having a left-handed child, when both parents are left-handed. Further studies are conducting to full gene map to this single gene theory (Jansen, 1998). But just recently, the scientists from the Wellcome Trust Centre for Human Genetics at Oxford University have lately discovered the gene LRRTM1, which they believe that increases the person’s chances to become left-handed. Over 40 scientists from 20 research centers revealed that this gene, the LRRTM1, is the first to be discovered which has an effect on handedness. Although little is known about LRRTM1, the Oxford team suspects that it modifies the development of asymmetry in the human brain. They also discovered that LRRTM1 might the risk to become schizophrenic, a brain disorder which results to impaired perception and thoughts. Yet, Dr. Clyde Franck, the leader of the Oxford team said that,” people really should not be concerned by this result. There were many factors which make individuals more likely to develop schizophrenic and the vast majority of left-handers will never develop a problem. We do not yet know the precise role of this gene.” Further research is still being conducted for the information with regard to this gene (Science Daily, 2007). Handedness is due to environmental influences, but genes also play a part. Only about one in every 50 left-handed children has parents who are both right-handed. And only about one out of six left-handed child parents who is a right hander and a left-hander. And one in every two left-handed child has a parent who are both left-handed (Hockenbury, 1997).

As Jansen (1998) stated that, Left-handed parents are most likely to have left-handed children. It has been demonstrated that handedness runs in the families, but of course environmental pressure must also be considered, for parents may purposefully or incidentally teach their children to be right-handed or left-handed. Adoption studies suggest that handedness is under genetic control as the results indicate the handedness of adopted children is more likely to follow that of their birth parents that their adopted parents.

If both parents are left-handed, 50 percent of the kids will be left-handed too. But if both parents are right-handed, only two percent of the kids will be left-handed (de Kay, 1979). There is a 30 percent case of left-handedness in a family pattern. When both parents are left-handed, there is a greater chance of having a left-handed child, but still, this does not follow a pattern (Myers, 1986). Older mothers are more likely to produce left-handed children than younger mother (de Kay, 1979). In a research made by Chris McManus, a professor of psychology, he stated that as women ages and bears a child, there will be a high percentage or probability to having a left-handed child, for a reason that older women are more likely to have left-handed child (Dewey, 1966). There is also a high percentage of left-handedness in twins, but it is rare to find both left-handed (de Kay, 1979). Among identical twins, one would likely be a left-hander and the other one is right-hander. A slight displacement of internal parts of developing egg might be the reason for this (Myers, 1986). Just in the case of the Olsen twins from the Hollywood, Mary Kate is a left-hander while her identical twin, Ashley is a right-hander. Virtually all pediatricians will agree that if a child has a preference for the left hand, it will show up by age of five (de Kay, 1979). But some experts claim that they can spot a left-hander during infancy. The whorl of their hair, it said, will twist counter-clockwise (de Kay, 1979). Half of the counter-clockwise whorl prefer left hand. Asymmetrical organization of the brain may also link to handedness and whorl of hair (Dewey, 1966). Aside from genetic involvement, even before birth, hand preference has already been demonstrated. Peter G. Hopper, together with other psychologists, observed 200 developing fetuses with the use of ultrasound, 95 percent sucked their right thumb while the other five percent sucked their left thumb. This figure is very close to the population number of the left and right-handed people today (Munn, 1951). While according to George Michel (1981), for the first two days after birth, they observed that in 150 babies, almost two-thirds preferred to lie with their heads turned to their right. At the age of five months “head right” babies reached for things with their right hands, while “head left” babies reached them with their left hands. With these studies, he conducted that handedness is genetically influenced (Myers, 1986). James de Kay (1979) stated that, “the brain is made up of two very different hemispheres. We need both, but for different reasons, since each has its own functions, its own personality, its own specialties, and most significantly, in reference to the subject under consideration, its own hands. “ Aside from the genetics and the hereditary basis to left-handedness, psychologists also claim that the dominant hemisphere of the brain may be responsible to the handedness of a person. Laterality in physiological psychology explains these phenomena. The left-handedness of a person might be caused by the brain and the asymmetry of the organs, the scientists and psychologists believes. Any left-handers or anything on their left side was controlled by the right brain. The hands were controlled by the motor central of the brain; in the case of the left-handers, dominant motor centers are in their right brain. Researchers hypothesized that left-handedness is due to brain abnormality in the left hemisphere of the brain. They assume that the early damage in the left hemisphere causes the shift of dominance to the right hemisphere of the brain; so does the premature brain, prolonged birth labor, breech birth and the tendency to become left-handed (Dewey, 1966). But many psychologists believe that the left side of the brain controls the right side of the body in a person, and therefore, it is said to be the dominant part of the brain. But it is unclear to them whether dominance is hereditary or just through use, but there are evidences that cerebral dominance is at least in part of the matter use (Huffman, 1990). During the Medieval Period, left-handers are said to be descendants of demons or Satan. They believe that left-handers are bewitched and most likely to cause chaos. Some left-handers, like the witches, were burned to death and suffered from great torture. “That long ago bias against left-handers is still with us,” stated de Kay (1979) in his book The Natural Superiority of the Left-Hander. He also stated that,

Actually, it was the Romans who made up all the rules against left-handers. They were the most militantly right-handed people in the world. The Romans invented the right-handed handshake, the fascist salute and the left to right alphabet that still causes a lot of trouble: The Roman word for “right” was “Dexter,” while their word for “left” was “Sinister.” In the Dark Ages, after the Roman Empire have collapsed, a lot of people gave up reading, writing, shaking hands and saluting, and went back to being left-handed. Once again, the tools invented in this period reflect a general ambidexterity. But by the Middle Ages left-handers were out in the cold. Even suits of armor were invariably right-handed.

During the 18th and 19th centuries, experts cited that there is a severe discrimination against left-handers. They have suggested that this might be the cause of dropping in number or population of the “gibble-fist.” But during the latter 20th century, the numbers picked up once again as the discrimination or social indifference faded. Yet, during the 1960’s, schoolchildren’s left hands were tied to force or ensure that they write on their right hands (The Sunday Times, 2007). Forcing a left-hander child to use their right hand could cause confusion and disturbance to his brain. It is frustrating for a child, and if put in under emergency circumstances, the nature will work its way and left hand will suddenly emerge to solve the problem (Myers, 1986). Forcing handedness may later develop into speech disorders. The reason is that it disturbs the natural dominance of the right cerebral cortex, which is the normal for him. But this could be cured by deliberately switching back to the left hand which may take a longer time (Huffman, 1990). Left-handers have experienced discrimination and social indifference in countries like India, Indonesia, China and even America. Humans tend to use their non-natural hand when faced in cultural pressure, perform manual labor and after an accident (Dewey, 1966). Even the fossils of Paleolithic stone tools and weapons also showed that they were made for the right. The tracings or drawings of the Cro-Magnon, who were believed to be left-handed, were drawn by the right hand. And the sketches of men and women in Egyptian tombs also depict right hand usage. Yet, this symmetry was not considered to be part of their culture (Kassin, 1989). But these were contradictory to what de Kay (1979) have written in his book,

As far as human beings are concerned, as we know from cave drawings, in the early days there were plenty of right-handers, but there were plenty of left-handers, too. If Neanderthal men were exclusively right-handed, they would have invented right-handed tools, correct? Instead, they invented ambidextrous tools suited for either hand. Throughout much of ancient history, the left-handers had equal rights, and these were even true in writing. The Egyptians did not feel they had to write left to right. They wrote up, down, left or right, depending on whim. The Greeks wrote BOUSTRO-PHEDON style, with each line alternating down the page, first line left to right, next line right to left, then another left to right, etc. The Chinese, even to this day, write in vertical columns from right to left, which would indicate slightly left-handed preferences. In a Biblical note, the Israelites were twice defeated by a Benjaminite army of “700 picked men who were left-handed.”

Left-handers are believed to have shorter life span compared to right-handers. And there are a low percentage of left-handers who have reached the age of 85. These were clarified in the Psychology book written by Saul Kassin (1989), which stated that, “Psychologists may disagree about why there are relatively few left-handers in the elderly population, but all of them agree that the physical environment is designed more for the comfort and safety of the right-handers.” It only means that the man-made environment that we are living today is more “friendly” to right-handers compared to left-handers. And these may be hazardous to the safety of the left-handers. In the general population, there are twice as many left-handed artists, musicians, mathematicians and engineers compared to right-handers (Hockenbury, 1997). MichaelAngelo, Leonardo da Vinci, Pablo Picasso, Jimi Hendrix, Paul McCartney, Ringo Starr, Ludwig van Beethoven, Sting, Annie Lenox, Celine Dion, George Michael and Phil Collins are a few of left-handers who excel in the arts and the music industry. For the theater and movies, Marilyn Monroe, Charlie Choplin, Julia Roberts, Bruce Willis, Tom Cruise, Val Kilmer, Jim Henson, Robert DeNiro, Morgan Freeman, Tim Allen, Henry Ford, Glen Campbell, Angelina Jolie, and Judy Garland are all left-handed. In the field of sports, there are also numbers of left-handers who excel in their chosen fields. These are Manny Pacquiao and Oscar de la Hoya (boxing), Mark Spitz (swimming), Dorothy Hamill (figure skating), Rafael Nadal (lawn tennis), and Babe Ruth (baseball) to name a few. Historical and influential leaders like Napoleon Bonaparte, Adolf Hitler, Joan of Arc, Julius Caesar, Queen Victoria, Alexander the Great, Benjamin Franklin, Joseph Estrada, Bill Clinton, George H.W. Bush, Ronald Raegan, Harry Truman, Al Gore, Prince William, Prince Charles, John McCain and Barack Obama are all left-handers. The genius Albert Einstein, Nobel Peace Prize winner Marie Curie and Al Gore, the astronaut Buzz Aldrin are also left-handed; so as Bill Gates of the Microsoft Company and Oprah Winfrey, the first black American woman hailed as one of the multimillionaires in United States by Forbes Magazine. Left-handers, according to psychologists, have right-brain dominance; so as the right-handers who have left-brain dominance. Differences between the functions of the right brain and the left brain have already been well-defined. Left hemisphere handles language, while the right hemisphere is more specialized in spatial recognition (Science Daily, 2008). To understand more on these hemispheres specialization, let us compare the function of these hemispheres in tabular form (Plotnik, 1996).
Left Hemisphere Right Hemisphere
Verbal
(language related skill) Nonverbal
(understanding simple sentences and read simple words)
Mathematical
(generally for advance mathematics skill) Spatial
(solving spatial problems, such as arranging geometric designed blocks)
Analytic
(analyzing each information separately) Holistic
(information processing by combining parts into a whole)

The left hemisphere is specialized for language functions (Morris, 1990), such as:
• Speaking
• Reading
• Understanding languages
• Writing
• Analytical functions (such as math)

While the right hemisphere is for nonverbal abilities (Morris, 1990), such as:
• Musical abilities
• Perceptual and “spatio-manipulative” skills

According to de Kay (1979),

Generally speaking, people with a dominant “thinking” brain become right-handed, while those dominant “feeling” brain become left-handed. You might expect a right-hander to be verbal, analytical, and good at math, and a left-hander to be intuitive, and mystical, with a strong visual sense. In politics, maybe this is why cold, heartless conservatives are called “right-wingers,” and why dreamy, bleeding heart liberals are called “left-wingers.” A lot of hard evidences show that most left-handers­ because they are dominated by a different kind of brain­ are a distinctly kind of people. They literally think differently, even when solving the same problem as a right-hander. Right-handers adapt comfortably to abstraction. But left-handers tend to translate everything into visual imagery. Right-handers tend to think lineally, linking their ideas in logical order. Left-handers are more apt to think holistically, skipping over the details.

Statistically, intelligence between left-handers and right-handers has no clear differences. Left-handers are twice as many to right-handers who have special talents in art, music and mathematics. They suggested that unusual hormones behavior before birth; the dominant part of the language is the right hemisphere of the brain. Left-handed individual who are right hemisphere dominant become exceptional in the nonverbal field (Myers, 1986). Left-handers are labeled to as more feeling oriented and talented in the arts than the right-handers. But, this should not be interpreted or concluded that left-handers uses their so-called “right brain dominance or attributes” in this sense. Some studies also showed that left-handers and right-handers are both widely diverse. Behavior and intelligence are both broad and complex to be able to associate or explain it by handedness (Jansen, 1998).

LIST OF REFERENCES

A. Books

de Kay, J. T. (1979). The Natural Superiority of the Left-Hander. United Kingdom: Angus& Robertson Publishers. Hockenbury, D. H. (1997). Psychology. New York: Worth Pub.

Huffman, K. (1990). Psychology in Action. New York: John Wiley and Sons Inc.

Jansen, E. (1998). Teaching with the Brain in Mind. Virginia: Association for Supervision and Curriculum Development.

Kassin, S. (1989). Psychology, 3rd Ed. Upper Saddle River NJ: Prentice Hall

Left-Handers on Roll as Numbers Triple. (2007, September 16). The Sunday Times. pp. B-3

Lexicon University Encyclopedia. (1988). New York: Lexicon Publication

McMahon, F. B. (1986). Psychology: The Hybrid Science. Chicago, Illinois: The Dewey Press.

Morris, C. (1990). Psychology: An Introduction. Englewood, Cliff, NJ: Prentice Hall.

Munn, N. L. (1951). Psychology: The Fundamentals of Human Adjustment. Boston: Houghton, Mifflin.

Myers, D. G. (1986). Psychology. New York: Worth Publishers, Inc.

The New Encyclopedia Britannica. (1993). Chicago: Univ. of Chicago

Oxford University. (2007, August 6). Gene for Left-Handedness Identified. Science Daily.

Plotnik, R. (1996). Introduction to Psychology I. Boston: Brooks/Cole.

Ruch, F. L. (1971). Psychology and Life. Chicago: Scott, Foreman and Company.

B. Internet Source

Lance, W. (2006). Left-Handed Children in a Right-Handed World. Retrieved January 10, 2009, from iCHED.org Website: http://www.iched.org/cms/script/page.php

References: Huffman, K. (1990). Psychology in Action. Jansen, E. (1998). Teaching with the Brain in Mind. Kassin, S. (1989). Psychology, 3rd Ed. Morris, C. (1990). Psychology: An Introduction. Munn, N. L. (1951). Psychology: The Fundamentals of Human Adjustment. Myers, D. G. (1986). Psychology. The New Encyclopedia Britannica. (1993). Chicago: Univ. of Chicago Oxford University Plotnik, R. (1996). Introduction to Psychology I. Retrieved January 10, 2009, from iCHED.org Website: http://www.iched.org/cms/script/page.php

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