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Left-to-right alphabets can be written smudge-free and in proper "forward slant" with the left-hand if the paper is turned 1/4 turn clockwise (90 degrees to the right), and the left-hand is drawn toward the body on forward strokes, and left to right on upward strokes (as expressed in directionality of the text). It is also possible to do [[calligraphy]] in this posture with the left-hand, but using right-handed pen nibs. Otherwise, left-handed pen nibs are required in order to get the thick-to-thin stroke shapes correct for most "fonts", and the left-handed calligrapher is very likely to smudge the text. Left-handed pen nibs are not generally easy to find, and strokes may have to be done backwards from traditional right-handed calligraphic work rules to avoid nib jamming and splatter. Left-handed people have an advantage in learning 19th-century [[copperplate script|copperplate]] hands, which control line-width by pressure on the point.
Left-to-right alphabets can be written smudge-free and in proper "forward slant" with the left-hand if the paper is turned 1/4 turn clockwise (90 degrees to the right), and the left-hand is drawn toward the body on forward strokes, and left to right on upward strokes (as expressed in directionality of the text). It is also possible to do [[calligraphy]] in this posture with the left-hand, but using right-handed pen nibs. Otherwise, left-handed pen nibs are required in order to get the thick-to-thin stroke shapes correct for most "fonts", and the left-handed calligrapher is very likely to smudge the text. Left-handed pen nibs are not generally easy to find, and strokes may have to be done backwards from traditional right-handed calligraphic work rules to avoid nib jamming and splatter. Left-handed people have an advantage in learning 19th-century [[copperplate script|copperplate]] hands, which control line-width by pressure on the point.

== Correlations ==
===Intelligence===
In his book ''Right-Hand, Left-Hand'',<ref>[http://www.righthandlefthand.com/ Right-Hand, Left-Hand official website] Accessed June 2006.</ref> Chris McManus of [[University College London]] argues that the proportion of left-handers is increasing 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 increases their range of abilities, and the genes that determine left-handedness also govern development of the language centres of the brain.

===Income===
In a 2006 U.S. study, researchers from [[Lafayette College]] and [[Johns Hopkins University]] concluded that there was no scientifically significant correlation between handedness and earnings for the general population, but among college-educated people, left-handers earned 10 to 15% more than their right-handed counterparts.<ref>"[http://www.slate.com/id/2147842 Sinister and Rich: The evidence that lefties earn more]", by Joel Waldfogel. Appeared in ''[[Slate (magazine)|Slate]]'' on August 16, 2006.</ref>

===Politics===
{{See also|Handedness of Presidents of the United States}}
Of the seven most recent U.S. Presidents, four, including [[Barack Obama]], have been left-handed, while a fifth is said to have been ambidextrous: [[Ronald Reagan]], who was left-handed by birth,<ref>{{cite book
|last= McManus|first= Chris
| title= Right Hand, Left Hand: The Origins of Asymmetry in Brains, Bodies, Atoms and Cultures
|publisher= Harvard University Press |year= 2004
|isbn= 978-0-674-01613-2
}}</ref><ref>{{cite book
|last= Wright|first= Ed
|title= Left-handed History of the World
|publisher= Barnes & Noble |year= 2007
|isbn= 978-0-7607-8704-5
}}</ref><ref name="Vast-Consp">{{cite web
|url=http://www.washingtonpost.com/wp-dyn/content/article/2008/07/03/AR2008070303202.html
|title=A Vast Left-Handed Conspiracy|work=The Washington Post
| year = 2008 | accessdate = January 2011
}}</ref> became president after he defeated left-handed candidate [[George H. W. Bush]] in the Republican primary election. Four years earlier, Reagan had lost the Republican presidential primary to incumbent left-handed President [[Gerald Ford]]. George H. W. Bush succeeded Reagan and later ran for re-election against left-handers [[Bill Clinton]]<ref>{{cite web
|url=http://www.post-gazette.com/pg/08056/860162-294.stm
|title=Another left-handed president? It's looking that way
|work=Pittsburgh Post-Gazette
| month = February | year = 2008 | accessdate = January 2011
}}</ref> and [[Ross Perot]].<ref name="Vast-Consp" /> Clinton's second term opponents included Perot, and [[Bob Dole]] who had become left-handed when his right arm was paralyzed in combat 50 years earlier. Left-handed then-Senator Obama defeated left-handed Senator [[John McCain]] in his race for the presidency.<ref>{{cite web
|url=http://abcnews.go.com/Politics/Vote2008/Story?id=4326568&page=1
|title=Four Out of Five Recent Presidents Are Southpaws
|work=ABC News
| month = February | year = 2008 | accessdate = January 2012
}}</ref>


==See also==
==See also==

Revision as of 06:35, 22 May 2012

"Leftie" redirects here. For the political term, see Left-wing politics.
"Southpaw" redirects here. For other uses, see Southpaw (disambiguation).
A person writing the Dutch word "Linkshandig" (left-handed) with the left hand

Left-handedness (also known as sinistrality, sinistromanuality, or mancinism) is the preference for the left hand over the right for everyday activities such as writing. In ancient times it was seen as a sign of the devil, and was abhorred in many cultures. A variety of studies suggest that 10% of the world population is left-handed.[1]

Causes

Main article: Handedness
  • 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 that specific alleles of at least one of three single-nucleotide polymorphisms upstream of the already known LRRTM1 gene were linked to left-handedness.[3][4]
  • Twins theory: this theory postulates that left-handed individuals were originally part of an identical twin pair, with the right-handed twin fetus failing to develop early in development. Although Australian researchers claimed to have debunked[5] the related vanishing twin theory, it is re-examined in Rik Smits's book "The Puzzle of Left-Handedness (2012)", which considers the fact that twin children have a high frequency of left-handedness / right-handedness in the pair.[6]
  • Prenatal hormone imbalances may play a role in the gene expression for left-handedness. While the Geschwind–Galaburda testosterone hypothesis is often cited as cause, there is not any evidence to support the theory. However, more recent research has emerged suggesting that high prenatal estrogen exposure is a plausible alternative to Geschwind. In a study endorsed by the Centers for Disease Control (CDC), it is suggested that men who were prenatally exposed to diethylstilbestrol (a synthetic estrogen based fertility drug), are more likely to be left handed.[7]
  • Long-term impairment of the right hand: people with long-term impairment of the right hand are more likely to become left-handed.

Handwriting and written language

The 44th President of the United States, Barack Obama, is left-handed as were Presidents Clinton, George H. W. Bush, Reagan, and Ford.

Because writing when moving one's hand away from its side of the body can cause smudging if the outward side of the hand is allowed to drag across the writing, it is considered easier to write ABC... and other left-to-right-scripts with the right hand than with the left. Left-handed people who use Arabic, Persian, Urdu, Hebrew or any other right-to-left script do not have the same difficulties with writing. The right-to-left nature of these scripts prevents left-handers from running their hand on the ink as happens with left-to-right languages.

Left-to-right alphabets can be written smudge-free and in proper "forward slant" with the left-hand if the paper is turned 1/4 turn clockwise (90 degrees to the right), and the left-hand is drawn toward the body on forward strokes, and left to right on upward strokes (as expressed in directionality of the text). It is also possible to do calligraphy in this posture with the left-hand, but using right-handed pen nibs. Otherwise, left-handed pen nibs are required in order to get the thick-to-thin stroke shapes correct for most "fonts", and the left-handed calligrapher is very likely to smudge the text. Left-handed pen nibs are not generally easy to find, and strokes may have to be done backwards from traditional right-handed calligraphic work rules to avoid nib jamming and splatter. Left-handed people have an advantage in learning 19th-century copperplate hands, which control line-width by pressure on the point.

See also

Notes

  1. ^ Hardyck C, Petrinovich LF (1977). "Left-handedness". Psychol Bull. 84 (3): 385–404. doi:10.1037/0033-2909.84.3.385. PMID 859955.
  2. ^ Hopkins, B., Lems, W., Janssen, B. & Butterworth, G. (1987) Postural and motor asymmetries in newborns. Human Neurobiology 6:153–56
  3. ^ Francks et al. Molecular Psychiatry (2007) 12:1129-1139
  4. ^ Gene for left-handedness is found, http://news.bbc.co.uk/2/hi/health/6923577.stm, BBC, 31 July 2007
  5. ^ Vanishing twin theory debunked
  6. ^ How New Humans Are Made by Charles E. Boklage
  7. ^ Titus-Ernstoff; et al. (2003). "Psychosexual Characteristics of Men and Women Exposed Prenatally to Diethylstilbestrol". {{cite news}}: Explicit use of et al. in: |last= (help)
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