Left-handedness: Difference between revisions

Left-handedness is the preference for the left hand over the right for everyday activities such as writing. Most left-handed people exhibit some degree of ambidexterity.^[1] Left-handedness is relatively uncommon; 90 to 93 percent of the adult population is right-handed.

• Hand orientation is developed in fetuses, most commonly determined by observing which hand is predominantly held close to the mouth.^[2]
• In 2007, researchers discovered LRRTM1, the first gene linked to increased odds of being left-handed. ^[3][4]
• Long-term impairment of the right hand: People with long-term impairment of the right hand are more likely to become left-handed, even after their right hand heals.^{[citation needed]} Such long-term impairment is defined as eight months or more.
• Testosterone: Exposure to higher rates of testosterone before birth can lead to a left-handed child.^[5] This is the Geschwind theory, named after the neurologist who proposed it, Norman Geschwind. It suggests that variations in levels of testosterone during pregnancy shape the development of the fetal brain. Testosterone suppresses the growth of the left cerebral hemisphere and so more neurons migrate to the right hemisphere. The highly developed right hemisphere is now better suited to function as the center of language and handedness. The fetus is more likely to become left-handed, since the right hemisphere controls the left half of the body. The theory goes on to tie the exposure to higher levels of testosterone and the resultant right-hemisphere dominance to auto-immune disorders, learning disorders, dyslexia, and stuttering, as well as increased spatial ability.
• Mirror twins

There are many colloquial terms used to refer to a left-handed person, e.g. "southpaw". Some are just slang or jargon words, while others may be offensive or demeaning, either in context or in origin (ie the British use ‘cack-handed’). 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 sinestra, a Latin word meaning 'left'.^[6] Left hand shakes are a sign of disrespect – however the left hand shake is the standard in the international Scouting movement. In Hebrew, as well as in other ancient Semitic and Mesopotamian languages, the term "hand" was a symbol of power or custody.^[7] The left hand symbolized the power to shame society, and was used as a metaphor for misfortune, natural evil, or punishment from the gods. This metaphor survived ancient culture and was integrated into mainstream Christianity by early Catholic theologians as Ambrose of Milan^[8] to modern Protestant theologians such as Karl Barth^[9] to attribute natural evil to God in explaining God's omnipotence over the universe.

Meanings evolved from use of these terms in the ancient languages. In many European languages, "right" is not only a synonym for correctness, but also stands for authority and justice: German recht, French droit, Spanish derecho, Portuguese direito; in most Slavic languages the root prav is used in words carrying meanings of correctness or justice. The right hand has also historically been associated with skill: the Latin word for right-handed is dexter, as in dexterity; indeed, the Spanish term diestro and the Italian's destro, mean both "right-handed" and "skillful". In Irish, "deas" means "right side" and "nice". "Ciotóg" is the left hand and is related to "ciotach" meaning "awkward"^[10]; in French, "gauche" means "left" and is also a synonym of "maladroit", meaning "clumsy". Same for the Italian "maldestro" (literally "not right" with the term right here used as opposed to left and not to wrong) and the Dutch word "links".

Meanwhile, the English word sinister comes from the Latin word sinestra, which originally meant "left" but took on meanings of "evil" or "unlucky" by the Classical Latin era. Alternatively, 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.^{[citation needed]} The contemporary Italian word sinistra has both meanings of sinister and left (the masculine adjective for sinister being sinistro). The Spanish siniestra has both, too, although the 'left' meaning is less common and is usually expressed by izquierda,^[11] a Basque word that made its way into Portuguese too. 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" (sinistro means only "sinister"). Furthermore, in English, the expression "To have two left feet" refers to clumsiness in the domains of football or dancing.

The left side is often associated with awkwardness and clumsiness. The English expression "having two left feet", the Dutch expression "twee linkerhanden hebben", the Spanish expression "tener dos pies izquierdos", the German expression "zwei linke Hände haben", the Bulgarian expression "dve levi ratse", the French expression "avoir deux mains gauches" and the Czech expression "Mít obě ruce levé" ("to have two left hands") all mean being clumsy. Moreover, the German idiom "mit dem linken Fuß aufgestanden sein", the Spanish expression "levantarse con el pie izquierdo" and the french one "s'être levé du pied gauche" (literally, to have gotten up with the left foot) means to have a bad day and do everything wrong or unsuccessfully (like "to get out of the wrong side of the bed" in English).

In ancient China, the left has been the "bad" side. The adjective "left" (Chinese character: 左, Mandarin: zuǒ) means "improper" or "out of accord". For instance, the phrase "left path" (左道, Mandarin: zuǒdao) stands for illegal or immoral means. The pictograph for "left", 左 depicts a left hand attending to work. In contrast, the pictograph for "right", 右 (Mandarin: yòu) depicts a right hand in relation to the mouth, suggesting the act of eating. Contrast this pattern with the Muslim example below. At the same time, in modern Chinese conscience the left is firmly held as the dominant and "male" side, epitomized in the formula "man-left, woman-right".

In Welsh, the word chwith means left, but can also mean strange, awkward, or wrong. The phrase o'r chwith refers to an object being inside-out.^[12]

In some Spanish-speaking countries, to do something por izquierda means to engage in corrupt conduct or employ illegitimate means; whereas por derecha or a derechas means to do it the right (legitimate) way.^[13]

In Danish or Norwegian, the expression venstrehåndsarbejde or venstrehåndsarbeid (left-hand work) means "something that is done in a sloppy or unsatisfactory way"^{[citation needed]}. Additionally, one of the words for left-handed", kejthåndet" or "keivhendt", comes from words meaning wrong handed or not straight handed.

In Dutch, "twee linkerhanden hebben" (having two left hands) means that one is clumsy or is a very poor handyman. The English equivalent of the phrase is "being all thumbs".

In Finnish, the word oikea means both right (okay, correct) and right (the opposite of left).

In Hungarian, the word for right is jobb which also means better. The word for left is bal, and is used in expressions such as kétbalkezes ("having two left hands"), balszerencse (bad luck), bal lábbal kel fel ("get up (from bed) with the left leg", an omen that predicts a bad day coming up).

In Swedish, vänster means left. The term vänsterprassel means infidelity, adultery; cheating. From this term the verb vänstra (lit. "lefting") is derived.

In Ireland left handedness is called a "ciotógach" (kitt-oog) which is the Irish language term for left-handed. It is frequently used amongst Irish people, e.g. "she gave him a slap of the ciotógach after he insulted her at the bar" the word ciotógach is not derogatory and is held with affection amongst left-handed people.

The Scots term for left-handedness is corrie fistit. The term can be used to convey clumsiness. Another term for left-handedness is Heilan meaning Highland. The term refers to the one-time perception of Highlanders but came to be used to refer to awkward, backward and left-handedness.^{[citation needed]}

In some parts of the English-speaking world 'cack-handed' is slang for left-handed (it is also used to mean clumsy). The origin of this term is disputed, but some suggest it is derived from the Latin cacare, in reference to the habit of performing ablutions with the left hand, leaving the right hand 'clean'.^[14] However, other source suggest that it is derived from the Old Norse word keikr, meaning "bent backwards" ^[15] Australians frequently use "cacky-handed". A less common Australian slang word for a left-handed individual is the term Molly-Dooker, whose origins cannot be ascertained for certain.^[16]

Amongst Muslims, and in some societies including India, it is customary to use the left hand for cleaning oneself with water after defecating. The right hand is commonly known in contradistinction from the left, as the hand used for eating.^[17]

Even the word "ambidexterity" reflects the bias. Its intended meaning is, "skillful on 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". This bias is also apparent in the lesser-known antonym "ambisinistrous", which means "clumsy on both sides" and derives from the Latin root "sinister", which means "left".^[18]

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.^[19] Ballparks are often designed so that batters are facing east, so that the afternoon or evening sun does not shine in their eyes.^[20] This means that left-handed pitchers are throwing with their south-side arm.^[21] The Oxford English Dictionary lists a non-baseball citation for "south paw", meaning a punch with the left hand, as early as 1848,^[22] just three years after the first organized baseball game, with the note "(orig. U.S., in Baseball)."^[23]

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 the right foot in front of the 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 an orthodox stance which gives southpaws an advantage. In the popular boxing film series Rocky, the main character Rocky Balboa is a 'southpaw'.

Southpaw is also a term in professional wrestling, often giving them the advantage.

In tennis, southpaws hold the racket in their left hand. Because of this, their grip of the handle is supposedly adjusted in a slightly different style from right-handed players. Some world champion left-handed tennis players include Jimmy Connors, John McEnroe, Martina Navratilova, and Rafael Nadal.

Left-handed people are sometimes placed at a disadvantage by the prevalence of right-handed tools in society. Many tools and devices are designed to be comfortably used with the right hand. For example, (right-handed) scissors, a very common tool, are arranged so that the line being cut along can be seen by a right-handed user, but is obscured to a left-handed user. Furthermore, the handles are often molded in a way that is difficult for a left-hander to hold, and extensive use in such cases can lead to varying levels of discomfort. Most importantly, the scissoring or shearing action - how the blades work together (how they are attached at the pivot) - operates correctly for a right-hander, but a left-hander will tend to force the blades apart rather than shearing the target substance.^[24] So-called ambidextrous scissors do not help, since the cutting blades are still set right-handed.

The computer mouse is sometimes made to fit the right hand better. Many computer installations have the mouse placed on the right side, making it awkward for left-handers to use without moving the mouse to the other side of the keyboard. Some mouse drivers and operating systems allow the user to reconfigure the mouse buttons to reverse their functions. However, being left-handed does not always mean the person uses the mouse on a computer with the left hand; many left-handers can use the mouse right-handed because they learned it that way. An additional advantage is, when mousing with the right hand, a left-handed person can still write with his left hand. More unusual input devices such as trackballs are often handed in such a way that they can only be used in the right hand, with economics precluding against offering a left-handed model.

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 usually must be specially ordered or custom made.^[25]

The lack of left-handed tools and machines in many workplaces is not only a nuisance to many left-handers, but has actually placed them at peril. In fact, some factories have installed left-handed equipment after successful class-action lawsuits on behalf of left-handed employees.^{[citation needed]}

Left-handed scissors require inverting both the handles and the blades if the left-handed user is to fully see the progress of the cut. Right-handed scissors place the thumb's blade on the left side, while left-handed scissors have this on the right side. This ensures the left hand's motion draws the blades together while cutting, ensuring a cleaner cut. Mundial and Fiskars are companies that have produced truly left-handed scissors, inverting both the blades and the handles.^{[citation needed]}

Left-handed adaptations have even bridged the world of music; guitars are often made especially for left-handers, though generally at a higher cost, and with greatly reduced availability. There have even been inverted pianos where the deepest notes correspond to the rightmost keys instead of the leftmost.^[26] Inverted trumpets are made, too, but at a considerably higher cost. Although the trumpet's valves are normally designed to be operated with the right hand, the prevailing belief is that left-handed trumpeters aren't at a significant disadvantage. The French horn, for example, is played with the left hand, yet most horn players are right-handed.

Left-handed golf clubs were one of the earlier, and well-accepted, manifestations of a special version of an implement; the most notable left-handed-playing participant being Phil Mickelson (he is naturally right-handed).

Other items which are inconvenient for left-handers include tin-openers, potato peelers, corkscrews, rulers, number keys on keyboards, watches, chequebooks, boomerangs, measuring cups and pencil sharpeners.

It can be difficult for left-handed children to learn to write if the teacher does not take the student's left-handedness into account. In fact, even in the later 20th century, some UK schools were discouraging children from writing with their left hand, often seriously affecting the child's development (Hansard 1998). When properly done, left-handed writing is a mirror image to that of the right-hander, making the teaching process confusing for the right-handed teacher of a left-handed student. Some chairs are equipped with writing boards on the right side only, contributing to this behavior. The result is that many left-handed children learn to write with their hand curled around the pen so that it can meet the paper at the same angle as the right-hander and also to account for the front page of notebooks and binders, as the books open so you write on the right side, which puts the binding on the left side, inhibiting the left hand from writing freely. ^[27] Once this habit is formed, it is difficult to break.^[28] 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. In addition, constantly lifting and replacing the hand over fresh ink often causes smudging, causing problems for many left-handed students, especially in exam situations. When the left hand is held correctly, it is below the writing, as is typical for right-handers.

However, left-handed people who speak Arabic, Persian, Urdu, Hebrew or any other right-to-left language do not have the same difficulties with writing. The right-to-left nature of these languages prevents left-handers from running their hand on the ink as happens with left to right languages. Still, due to these alphabets being developed for right-handed people, the characters are still often more easily matched to a right-handed profile.

Left-handers also have an advantage in learning 19th-Century copperplate hands, which control line-width by pressure on the point, because the proper angle for the pen point is slanted "northeast," which puts the right hand in an awkward, "crabbed" position. Some pen makers make bent nibs to allow right-handers to point the pen in the direction that allows the best control.

The vast majority of firearms are designed for right-handed shooters, with the operating handle, magazine release, and/or safety mechanisms set up for manipulation by the right hand, and fired cartridge cases ejected to the right. Also, scopes and sights may be mounted in such a way as to require the shooter to place the rifle against the right shoulder. A left-handed shooter must either purchase a left-handed firearm (which are manufactured in smaller numbers and are generally more expensive and/or harder to obtain), shoot a right-handed gun left-handed (which presents certain difficulties, such as the controls being improperly located for them or hot shell cases being ejected towards their body, especially their eyes or down their collar or right sleeve), or learn to shoot right-handed (which may pose additional problems, primarily that of ocular dominance).

Fortunately for left-handed people, modern guns feature more ambidextrous or right/left-handed reversible operating parts than their predecessors (such as the H&K G36). Bullpup rifles are particularly problematic for left-handers unless they can be reconfigured, since empty shells would be ejected fast and straight into the shooter's face and cheek potentially causing injury. The British LA-85 Assault Rifle must be fired right-handed, placing left-handed soldiers at a disadvantage. In contrast the Steyr AUG is of a modular design, and the ejection port and extractor can be switched/replaced to suit the handedness of the soldier operating it. The M-16 and its variants have a fixed ejection port, but being a conventional (i.e. not bullpup) design the ejection port is forward of the operator and hence able to be fired either handed. Circa 1980, with the introduction of the M16A2 version, a case deflector was incorporated adjacent to the ejector port to direct discarded shells in a more forward direction, making the rifle even more left hand operator friendly.

Lever action and pump action firearms present fewer difficulties for left-handers than bolt action weapons do. Many weapons with adjustable sights allow for left-handed use, but a right eye dominant shooter is necessary to adjust. In fact, most weapons adjust well enough that a weapon will not eject shells into a left-hander's eye.

One of the few cameras ever produced for left-handers was the half-frame Yashica Samurai. Cameras predominantly have the hand grip, shutter release, film wind lever and commonly used selection buttons, switches and dials controlled by the right hand, lens controls (where present) tend to be accessible by either hand. When a left-handed person uses a right-handed camera the hand control can be less steady and hence produce camera shake leading to poorer pictures at low shutter speeds. When cameras were predominantly mechanical, or later electro mechanical, it would be difficult and hence expensive to produce a left-handed version of a right-handed camera.^{[citation needed]} Video-cameras also tend to have the handstrap on the rightside of the camera. Thus the camera must be held using the right hand, which often leads to a more shakey video being captured.

Most guitars are designed to be played right-handed ^{[citation needed]} (that is to say the right hand is used to strum or pick the strings while the left hand manipulates the fret board). Although a right-handed guitar may be converted for left-handed playing (as was most notably done by Jimi Hendrix, Paul McCartney, and Kurt Cobain), this always requires replacing the bridge and nut for the strings to fit and the intonation to be correct. This "quick alternative" to getting a "real" left handed guitar has only been necessary due to a considerable lack of true left handed instruments, manufactured specifically for the left handed player. In addition while it may feel natural to use the right hand as the "fret" hand (opposite the a right handed person) it is becoming archaic to teach the neophite this application. It's actually advantageous for a left handed person to play a guitar as a right handed person because the modern playing style requires more precise and versatile movement from the hand fretting the notes than plucking the strings. This was not always the case in early guitar where the right hand was needed to master complex rhythm syncopation and finger independence. Many guitar brands do make left handed versions of their popular products. Several known companies such as Ernie Ball, Fender,Gibson have been producing left versions of their guitars. Many other guitar companies as well choose to include a "left handed" version of their product to expand upon sales as well. Although several major guitar companies have stopped making left handed guitars altogether, notably Paul Reed Smith in 2006, and Rickenbacker in 2008.^{[citation needed]} Gaskell Guitars, a brand from Australia, specializes in left-handed guitars only. Of those companies that do make some left-handed versions of their products, most penalize the left-handed guitarist by imposing a 10-20% surcharge on the cost.

In his book Right-Hand, Left-Hand,^[29] 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 centres of the brain.

McManus also says that the increase in the 20th century of people identifying as left-handed could produce a corresponding intellectual advance and a leap in the number of mathematical, sporting, or artistic geniuses.

In 2006, researchers at Lafayette College and Johns Hopkins University in a study found that left-handed men are 15 percent richer than right-handed men for those who attended college, and 26 percent richer if they graduated. The wage difference remains unexplained, and does not appear to apply to women.^[30]

See: Handedness of Presidents of the United States

Studies show that left-handedness does not necessarily correspond with "left-sidedness" (such as using your left foot to kick), although most left-handed people tend to have "left-sidedness". The same effect holds with ocular dominance. It has also been found that people have dominant sides of the body, such as the eye, foot, and ear.

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.^{[31][32][33][34]}

According to this theory, right-handed people 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.^[35]

Left-handed persons are thought to process information using a "visual simultaneous" method in which several threads can be processed simultaneously^[36]. There is another way to view this, by way of analogy: Suppose there were one thousand pieces of popcorn and one of them was colored blue. Right-handed people—using the linear sequential processing style—would look at the popcorn one at a time until they encountered the blue one. The left-handed person would spread out the pieces of popcorn and look at all of them to find the one that was blue. A side effect of these differing styles of processing is that right-handers need to complete one task before they can start the next. Left-handers, by contrast, are capable and comfortable switching between tasks.^[37] This seems to suggest that left-handed people have an excellent ability to multi-task, and anecdotal evidence that they are more creative may stem from this ability to multi-task.^[38]

According to research conducted by Dr. Roger Sperry, 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.^[39] 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.^[40]

The hypothesis that left-handed people are predisposed to visual-based thought has been validated by a variety of evidence. In the 2004 book Brains That Work a Little Bit Differently^[41], researchers Allen D. Bragdon and David Gamon, Ph.D., briefly described some of the current research on handedness and its significance. "Handedness researchers Stanley Coren and Clare Porac have shown that left-handed university students are more likely to major in visually-based, as opposed to language-based subjects. Another sample of 103 art students found an astounding 47 percent were left- or mixed-handed". [page 76]

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.

• Right-handed
• Cross-dominance
• Handedness
• LRRTM1
• Laterality
• Chirality (chemistry)
• Chirality (mathematics)
• Chirality (physics)
• The Tale of Cross-eyed Lefty from Tula and the Steel Flea
• Geschwind–Galaburda hypothesis
• Situs inversus
• Handedness and sexual orientation
• Handedness of Presidents of the United States
• Handedness and mathematical ability

Look up left-handedness in Wiktionary, the free dictionary.

Wikimedia Commons has media related to Left-handedness.

• Lefties Have The Advantage In Adversarial Situations, ScienceDaily, April 14, 2006.
• Science Creative Quarterly's overview of some of the genetic underpinnings of left-handedness
• Quirks & Quarks June 10, 2006 (CBC radio documentary on left-handedness including interviews with four scientists holding different views on the determinants of handedness)
• A left-handed senior citizen recalls the emotional torment he faced at a New York public school in the 1920s. (Audio slideshow)
• Famous Left-Handers
• Schwartz, Alyssa (2005). "Lefties face increased breast cancer risk", C-Health News, 30 September.
• Scans may 'cause brain changes', BBC News.
• Hansard (1998) ‘Left-handed Children’, Debate contribution by the Rt Hon. Mr. Peter Luff (MP for Mid-Worcestershire), House of Commons, 22 July.
• A 1918 Popular Science Monthly article on left-handedness -- Is your Child Left-Handed? Why, according to psychological tests, left-handed people ought to remain so, Popular Science monthly, December 1918, page 22, Scanned by Google Books: http://books.google.com/books?id=EikDAAAAMBAJ&pg=PA22