Left-handed

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(Redirected from Left handed)

For other uses, see Left-handed (disambiguation).

"Southpaw" redirects here; for other uses, see Southpaw (disambiguation).

A person who is left-handed primarily uses his or her left hand, more so than the right hand; a left-hander will probably use the left hand for tasks such as personal care, cooking, and so on. Writing is not as precise an indicator of handedness as it might seem, because many left-handed people write with their right hand but use their left hand for other tasks.

[edit] Demographics

Approximately 8 to 15% of the adult population is left-handed.<ref>Hardyck, C., & Petrinovich, L. F. (1977). "Left-handedness," Psychological Bulletin, 84, 385–404.</ref> Studies indicate that left-handedness is more common in males than females.<ref>Raymond, M.; Pontier, D.; Dufour, A.; and Pape, M. (1996). |Frequency-dependent maintenance of left-handedness in humans," Proceedings of the Royal Society of London, B, 263, 1627-1633</ref> Left-handedness, in comparison to the general population, also appears to occur more frequently in identical twins,<ref>Twinning Facts - National Organization of Mothers of Twins Clubs, Inc.. Accessed June 2006.</ref> and several groups of neurologically disordered individuals (people suffering from epilepsy,<ref>Schachter, S. C.; Boulton, A.; Manoach, D.; O'Connor, M.; Weintraub, S.; Blume, H.; & Schomer D. L. (1995). "Handedness in patients with intractable epilepsy: Correlations with side of temporal lobectomy and gender," Journal of Epilepsy, 8, 190–192.</ref> Down's Syndrome,<ref>Batheja, M., & McManus, I. C. (1985). "Handedness in the mentally handicapped," Developmental Medicine and Child Neurology, 27, 63–68.</ref> autism,<ref>Cornish, K. M., & McManus, I. C. (1996). "Hand preference and hand skill in children with autism," Journal of Autism and Developmental Disorders, 26, 597–609.</ref> mental retardation<ref>Grouios, G.; Sakadami, N.; Poderi, A.; & Alevriadou, A. (1999). "Excess of non-right handedness among individuals with intellectual disability: Experimental evidence and possible explanations," Journal of Intellectual Disability Research, 43, 306–313.</ref>, dyslexia, etc.) Statistically, the identical twin of a left-handed person has a 76% chance of being left-handed, identifying the cause(s) as partly genetic and partly environmental.<ref>Ask Yahoo!: Why am I right-handed, but my brother is left-handed? Accessed June 2006.</ref>

[edit] Causes of left-handedness

See main article at handedness.

Testosterone: According to one theory, exposure to higher rates of testosterone before birth can lead to a left-handed child.

Birth stress theory: Left-handedness may not be due to stress at birth.

Ultrasound theory: A popular theory is that ultrasound scans may affect the brain of unborn children, causing higher rates of left-handedness in mothers who have ultrasound scans compared to those who do not. This is probably based on a few studies <ref>“Routine ultrasonography in utero and subsequent handedness and neurological development”, K.A. Salvesen, L.J. Vatten, S.H. Eik-Nes, K. Hugdahl, L.S. Bakketeig, British Medical Journal, Vol. 307, 1993,159-64.</ref> <ref>“Routine ultrasound screening in pregnancy and children’s subsequent handedness.” H. Kieler, O. Axelsson, B. Haglund, S. Nilsson, K.A. Salvesen, Early Human Development, Vol. 50, 1998, 233-45.</ref>where this relation is studied. In one of these the authors claim that "...we found a possible association between routine ultrasonography in utero and subsequent non-right handedness among children in primary school." However later in the same article the authors state that "Thus the association ... may be due to chance" and "The result was not significant, suggesting that the study had insufficient statistical power to resolve the relationship between ultrasonography and subsequent left handedness in the child"

Although highly backed arguments, none of these can be completely true. There have been cases, for example, when one identical twin is left-handed, and the other is right-handed; this is contradictory to all of the above theories.*

This is not always the case. Susceptibility and exposure also come into play. Environmental factors, such as blood flow or positioning in the womb, may limit the hormone's impact on one of twins. Identical twins have the same DNA - having left and right handed twins only suggests that the DNA is not the sole factor.

[edit] Social stigma and repression of left-handedness

[edit] Common names for left-handedness

There are many colloquial terms used to refer to a left-handed person. Some are just slang or jargon words, while others may be offensive either in context or in origin. In more technical contexts, 'sinistral' may be used in place of 'left-handed' and 'sinistrality' in place of 'left-handedness'. Both of these technical terms derive from sinister, a Latin word meaning 'left'<ref>yourDictionary Word of the Day: sinistral. Accessed June 2006.</ref>.

[edit] Southpaw

A left-handed individual may be known as a southpaw, particularly in a sports context. It is widely accepted that the term originated in the United States, in the game of baseball<ref>[1]. Accessed August 2006.</ref>. Ballparks are often designed so that the batter is facing east, in order that the afternoon or evening sun does not shine in his eyes. This means that left-handed pitchers are throwing from the south side. The first use of the term is credited to Finley Peter Dunne. However, the Oxford English Dictionary lists a non-baseball citation for "south paw", meaning a punch with the left hand, as early as 1848<ref>Morris, Evan (1995). Word detective research. Accessed June 2006.</ref>, just three years after the first organized baseball game.

In boxing, someone who boxes left-handed is frequently referred to as southpaw. The term is also used to refer to a stance in which the boxer places his right foot in front of his left, so it is possible for a right-handed boxer to box with a southpaw stance. Most boxers, southpaw or otherwise, tend to train with sparring partners who adopt a right-handed stance, which gives southpaws an advantage.

[edit] Ciotóg

Ciotóg is an Irish word used to describe left-handed people, which also means 'strange person'<ref> "My Left Foot," The Kingdom, 24 July, 2003. Accessed June 2006.</ref>.

[edit] Linguistic suggestion

Some left-handed people consider themselves oppressed, even to the point of prejudice. Etymology often lends weight to the argument:

In many European languages, "right" stands for authority and justice: German and Dutch, recht, French, droit, Spanish, diestro; in most Slavic languages the root prav is used in words carrying meanings of correctness or justice. Being right-handed has also historically been thought of as being skillful: the Latin word for right-handed is "dexter," as in dexterity; indeed, the Spanish term diestro means both "right-handed" and "skillful".

Meanwhile, the English word "sinister" comes from Latin and it originally meant "left" but took on meanings of "evil" or "unlucky" by time of the Classical Latin era. "Sinister" comes from the Latin word sinus meaning "pocket": a traditional Roman toga had only one pocket, located on the left side for the convenience of a right-handed wearer. The contemporary Italian word sinistra has both meanings of sinister and left. The Spanish siniestra has both, too, although the 'left' meaning is less common and is usually expressed by 'izquierda,'<ref>Etimología de izquierda, deChile.com. Accessed June 2006. (Spanish)</ref> a Basque word. A left-hander was supposed to be not only unlucky, but also awkward and clumsy, as shown in the French gauche and the German links and linkisch. As these are all very old words, they support theories indicating that the predominance of right-handedness is an extremely old phenomenon. In Portuguese, the most common word for left-handed person, canhoto, was once used to identify the devil, and canhestro, a related word, means "clumsy".

In ancient China, the left has been the "bad" side. The adjective "left" (左 Mandarin: zuo) means "improper" or "out of accord." For instance, the phrase "left path" (左道 Mandarin: zuodao) stands for illegal or immoral means. In some parts of China, some adults can still remember suffering for the "crime" (with suitable traumatic punishments) of not learning to be right-handed in both primary and secondary schools, as well as in some "keeping-good-face" families.

In Norwegian, the expression venstrehåndsarbeid (left-hand work) means "something that is done in a sloppy or insatisfactory way".

Even the word "ambidexterity" reflects the bias. Its intended meaning is, "skillful at both sides." However, since it keeps the Latin root "dexter," which means "right," it ends up conveying the idea of being "right-handed at both sides."

[edit] Inaccessibility of implements and skills

Image:Japanese knife blade types.png

Left-handed people are placed at a constant disadvantage by society. Nearly all tools and devices are designed to be comfortably used with the right hand. For example, scissors, a very common tool, are arranged so that the line being cut along can be seen by a right-handed user, but is not visible to a left-handed user. Furthermore, the handles are often molded in a way that is very difficult for a left-hander to hold, and extensive use can lead to severe discomfort. The mouse on many computers are also sometimes made to fit the right hand only. Rulers as well can be difficult to use, being often designed in a manner that forces left-handers to measure items upside-down. While European-style kitchen knives are symmetrical, Japanese kitchen knives have the cutting edge ground asymmetrically, with ratios ranging from 70-30 for the average chef's knife, to 90-10 for professional sushi chef knives; left-handed models are rare, and must be special ordered and custom made. <ref> "How to Succeed at Knife-Sharpening Without Losing a Thumb" New York Times, September 23, 2006. Accessed September 23, 2006.</ref>

Writing is difficult to learn for a left-handed child if, as is usually the case, the writing teacher refuses to teach left-handed children in a way that is easy for them. This is because, when properly done, left-handed writing is a mirror image to that of the right-hander, making the learning process confusing for the left-handed student. The result is that the majority of left-handed people write with their hand curled around the pen so that it can meet the paper at the same angle as the right hander, rather than simply tilt the paper the opposite way. Once this habit is formed, it is difficult to break. This curling of the hand results in the heel of the palm being placed behind the writing, forcing the writer to lift it off the paper and making the grip even more awkward. When the left hand is held correctly, it is below the writing, as is typical for right-handers.

Left-handed people in the Arab world and Israel face the same challenges, even though writing in their languages runs right to left, causing right-handers to run their hand on the ink. And, they're all confused.

[edit] Cultural stigmatisation

Until the latter part of the twentieth century, Roman Catholic nuns in United States elementary schools would punish children for using their left hand to write, typically by slapping their left hand with a ruler if they attempted to pick up a pen with it. ^{[citation needed]} As late as the early 20th century, school teachers in the Netherlands would force right-handed writing (thus, ambidexterity) on left-handed writing children. ^{[citation needed]} An example of such treatment involves baseball players Lou Gehrig and Babe Ruth, who both hit and threw left-handed and wrote right-handed after enduring left-handed suppression during their formative years. ^{[citation needed]}

Left-handedness was often interpreted as a sign of Satanic influence, and thus prohibited. Many examples can be found in the Christian-Greek scriptures in which the wicked or evil sit at the left hand of God, while the righteous sit at the right hand of God, during the Last Judgment. The Inuit also believed that every left-handed person was a sorcerer. ^{[citation needed]}

The Romans also frowned upon left-handedness. A left-handed boy who was training to be in a Roman legion would have his hand bound to his side, and would be forced to use the gladius with his right hand. This was done out of necessity, as a left-handed Roman would have interfered with the cohesion of the Roman legions.

The use of left hand was also frowned upon in Asia. Allegedly, though there were few examples of its happening, a Japanese man could once divorce his wife if he discovered that she was left-handed.

Until very recently, in Chinese societies, left-handed people were strongly encouraged to switch to being right-handed. However, this may be in part because, while Latin characters are equally easy to write with either hand, it is more difficult to write legible Chinese characters with the left hand. The prescribed direction of writing each line of a Chinese character is designed for the movements of the right hand, and some shapes tend to feel awkward to follow with the left hand's fingers. It results in a less soft writing than it would be with the right hand.

In many parts of the world, such as Indonesia, it is considered impolite to eat and accept gifts with the left hand. The reason for this is that a person who uses his left hand to eat would often cause trouble with the person to the left of him. Another stated reason for this is that the left hand is used in some countries, like Indonesia, during a bathroom visit.

A profound Arab stigma against left-handedness dates to a pre-industrial period when paper was extremely rare and (in desert regions) water was too precious to be used for hand-washing. Because it was necessary to use one hand for wiping oneself after defecation, and because it was impossible to cleanse this hand thoroughly, the hand used for this task (traditionally, the left hand) was deemed unfit to be used for any other activity, especially as most Arabs of that time lacked eating utensils, and so they ate with their fingers (of the right hand) from communal dishes, while keeping the left hand entirely concealed at mealtime. To this day, it is widely regarded as taboo in Arab culture to handle food with the left hand. Offering one's left hand for a handshake greeting, or even waving it in greeting without touching, would be considered a serious personal insult in Arab society.

[edit] Famous left-handed people

Despite the suppression, there have been many famous left-handed people, and the associated right brain hemisphere that is said to be more active in left-handed people has been found in some circumstances to be associated with genius and is correlated with artistic and visual skill.

Many members of the British royal family are left-handed. Genetic factors are generally used to explain this. King George VI (who was the younger brother of Edward VIII, and therefore not expected to inherit the throne) was left-handed. During his boyhood and adolescence, his father George V required the prince to wear a long string tied to his left wrist; whenever he used his left hand, his father would tug the string violently, hoping to train him to become right-handed. George VI's severe stammer may or may not have developed as a result of this. John Heard, star of the cult hit C.H.U.D. is left-handed. Nelson Rockefeller was also left-handed; his father used this same string technique in an equally unsuccessful attempt to switch him to right-handedness. Mark I. Moore, the famous environmentalist, is an example of a left handed person who bats right handed. He's also a vegetarian.

As visual thinking is much promoted in modern society, left-handers have gained increasing amounts of respect. As well, in certain fields, left-handedness is advantageous; these include a number of sports (see section below).

[edit] Left-handedness and intelligence

A common belief suggests that left-handed people are more intelligent or creative than right-handed people. While there is an unresolved debate within the scientific community on how to operationalize both intelligence and creativity, some studies have demonstrated a small positive correlation between left-handedness and creativity/intelligence.

In his book Right-Hand, Left-Hand,<ref>Right-Hand, Left-Hand official website Accessed June 2006.</ref> Chris McManus of University College London, argues that the proportion of left-handers is rising and left-handed people as a group have historically produced an above-average quota of high achievers. He says that left-handers' brains are structured differently in a way that widens their range of abilities, and the genes that determine left-handedness also govern development of the language centers of the brain.

In Britain, around 11% of men and women aged 15-24 are now left-handed, compared to just 3% in the 55-64 age category.<ref>Steele, James & Mays, Simon (1995). New findings on the frequency of left- and right-handedness in mediaeval Britain.</ref> McManus suggests a number of factors that may be driving this increase:

Left-handers were severely discriminated against during the 18th and 19th centuries and it was often "beaten out" of people
In adulthood, left-handers were often shunned by society, resulting in fewer marrying and reproducing
As discrimination declined in the 20th century, the number of natural left-handers who stayed left-handed increased
The rising age of motherhood contributed as, statistically, older mothers are more likely to give birth to left-handed children

McManus says that the increase could produce a corresponding intellectual advance and a leap in the number of mathematical, sporting, or artistic geniuses.

Unfortunately, they tend to be over-represented at both ends of the intellectual scale, and as well as geniuses, the group also produces a disproportionately high number of those with learning handicaps. There have been suggestions of links between left-handedness and dyslexia, stuttering, and child autism, among other disabilities.^{[citation needed]}

In 2006, researchers at Lafayette College and Johns Hopkins University in a study found that left-handed men are 15% richer than right-handed men for those who attended college, and 26% richer if they graduated. The wage difference is still unexplainable and does not appear to apply to women.<ref>"Sinister and Rich: The evidence that lefties earn more", by Joel Waldfogel. Appeared in Slate on August 16, 2006.</ref>

As well as possible intelligence advantages, being left-handed can also bring about other benefits, including:

Brain hemisphere division of labor: The premise of this theory is that since both speaking and handiwork require fine motor skills, having one hemisphere of the brain do both would be more efficient than having it divided up. ^{[citation needed]}
Advantage in hand-to-hand combat: Left-handers have a 'surprise' factor in combat, since the majority of the population is right-handed.

It has been said that being left-handed has an effect on one's sexual preference. Some have argued that left-handed people have a higher probabillity of being homosexual than right-handed people because of their thought process, "visual simultaneous", but this claim has been disregarded as a myth due to lack of scientific evidence.

[edit] "Disappearing" left-handers

Statistics show that older people are less likely to be left-handed than their younger counterparts — the percentages of left-handed people sharply drop off with increased age. In America, 12% of 20 year olds are left-handed, while only 5% of 50 year olds and less than 1% of people over 80 are.

A study<ref>LEFT HANDERS EARLY DEATH MYSTERY, 5 articles thereon. Accessed September 2006.</ref> (no longer deemed credible) published in 1991 claimed that these statistics indicate that left-handed peoples' lifespans are shorter than those of their right-handed counterparts by as much as 9 years. They explained this gap by asserting that left-handed people are more likely to die in accidents as a result of their "affliction," which renders them clumsier and ill-equipped to survive in a right-handed world.

Researchers now attribute most of the difference between the age groups to the fact that older people would be more likely to have experienced pressure to switch hands, a factor not affecting the younger generations. This is supported by the fact that more women than men switched hands, and women on average live longer than men. However, this reasoning cannot explain all variation, and the case of the "disappearing southpaws" remains a mystery.

Another theory is that some left-handed people switch hands later in life, due to conformist pressures, or a "biological imperative." It has also been suggested that the percentage of children born left-handed may have been increasing over time.

[edit] Left-handers in sports

There are many left-handers in sports; however, a written rule in polo states that one must not hold a stick in his or her left hand.<ref>Rule A.1(c), The International Rules for Polo, Federation of International Polo, 2002. (PDF) Accessed July 7, 2006.</ref> There are very few left-handed professionals in polo; all are required to use their right hand.^{[citation needed]}

In field hockey, right-handed play is effectively required (though not explicitly so) because one rule states that the ball cannot be played with the back of the stick<ref>Rule 9.5, Rules of Hockey Including Explanations, The International Hockey Federation, 2006. (PDF) Accessed July 7, 2006.</ref> while another specifies that the stick be flat on its left side,<ref>Rule 4.6, Rules of Hockey Including Explanations, The International Hockey Federation, 2006. (PDF) Accessed July 7, 2006.</ref> which would be the "natural" side for a right-handed player, but when playing with the stick in one hand (playing reverse), this can give an advantage back to the left-handers. Having all players play with the same handedness is essential to keeping hockey a non-contact sport: a left-hander and a right-hander competing for the ball would tend to collide. All-left-hander matches are possible, but rare.

On the other hand, being left-handed can be an advantage in many sports. For example, in fencing, a right-handed fencer is more accustomed to facing another right-handed fencer simply because being right-handed is more common. A left-handed fencer is also more accustomed to facing a right-handed opponent for the same reasons. Therefore, when a right-handed fencer faces a left-handed opponent, the right-hander is not as used to fighting a left-hander as the left-hander is used to fighting a right-hander, causing a slight yet noticeable advantage. The same advantage may be present for most one-on-one or face-to-face sporting events. Baseball is particularly suited to left-handed hitters for three reasons: left-handers are already a step or two closer to first base in their batter's box before they even hit the ball so are more likely to beat out close plays; many baseball parks have shorter right field fences which gives left-handed sluggers a few more home runs that would otherwise be outs; and finally, most pitchers are right-handed which gives the left-handed hitter a better angle to see the ball and causes curve and sliding pitches to move towards them, rather than away. That is why a good switch hitter is considered valuable.

In football (soccer), left-handed players are often more skilled at playing with the left foot (though being left-handed does not necessarily result in being left-footed), which makes them valuable as they can play better on the left side of the field than right-handed players. Interestingly, in the sport of ice hockey, there are many more left-handed shooters, and the majority of goaltenders catch with their left hand (forcing many opponents to shoot left-handed, in the process). In tennis, left-handers impart spin on the ball that is opposite of that which a right hander would hit. As a result, right-handed players (who are accustomed to playing right handers) have difficulty dealing with a left-hander's shots which curve in a direction opposite to what they are accustomed to facing.

Minor sports where left-handedness is an significant advantage include Eaton Fives, where the buttress is on the left, the idea serve placing the ball at the bottom corner - almost impossible for a right-handed player to reach. Another is Real (Royal) Tennis, in which the serve along the penthouse is far easier with the left hand than with the right.

[edit] Left-sidedness

[edit] Traffic flow

It is argued that Napoleon's left-handedness contributed to traffic flowing on the right side of the road in post-revolutionary France. The reasoning behind this evolution stems from Napoleon having to fight in wars with his sword in his left hand and that he reportedly converted his army to fight the same way. This would have entailed the French cavalry of the day to approach opponents from their right.

[edit] In humans

Studies show that left-handedness does not necessarily correspond with "left-sidedness." (Using your left foot to kick with, for example.) The same thing holds with "eyedness."

[edit] Possible effects in humans on thinking

There are many theories on how being left-handed affects the way a person thinks. One theory divides left- and right-handed thinkers into two camps: visual simultaneous vs. linear sequential.<ref>http://www.anthonyhempell.com/papers/tetrad/visual.html</ref><ref>http://www.giftedservices.com.au/visualthinking.html</ref><ref>http://www.arty4ever.com/right/brain.htm</ref><ref>http://painting.about.com/library/blpaint/blrightbrain.htm</ref>

According to this theory, right-handed persons are thought to process information using a "linear sequential" method in which one thread must complete its processing before the next thread can be started.

Left-handed persons are thought to process information using a "visual simultaneous" method in which several threads can be processed simultaneously. Another way to view this is such: Suppose there were a thousand pieces of popcorn and one of them was colored pink. The right-handed person — using the linear sequential processing style — would look at the popcorn one at a time until they encountered the pink one. The left-handed person would spread out the pieces of popcorn and visually look at all of them to find the one that was pink. A side effect of these differing styles of processing is that right handed persons need to complete one task before they can start the next. Left-handed people, by contrast, are capable and comfortable switching between tasks. This makes them appear (to the right-handed majority) as if they do not finish anything. Alternately, left-handed people have an excellent ability to multi-task. Perhaps the anecdotal evidence that suggests they are more creative stems from this ability to multi-task.

Right-handed people process information using "analysis", which is the method of solving a problem by breaking it down to its pieces and analyzing the pieces one at a time. By contrast, left-handed people process information using "synthesis", which is the method of solving a problem by looking at the whole and trying to use pattern-matching to solve the problem. Ultimately, being left-handed is not an all-or-nothing situation. The processing styles operate on a continuum where some people are more visual-simultaneous and others are more linear-sequential. Also, it is very difficult to ascertain the way a human being behaves within the black box that is the brain. Whether this theory about processing styles is valid or not will be borne out by future experimentation.

[edit] In animals

Most primates also exhibit a preference for using one hand over the other although their populations are not necessarily right-hand preferential. It is a common legend that most polar bears are left-handed.^{[citation needed]}