Editing Handedness (section)

== Correlation with other factors ==
The modern turn in handedness research has been towards emphasizing degree rather than direction of handedness as a critical variable.<ref>{{cite journal |last1=Prichard |first1=Eric |last2=Propper |first2=Ruth E. |last3=Christman |first3=Stephen D. |title=Degree of Handedness, but not Direction, is a Systematic Predictor of Cognitive Performance |journal=Frontiers in Psychology |date=2013 |volume=4 |page=9 |doi=10.3389/fpsyg.2013.00009 |doi-access=free |pmid=23386836 |pmc=3560368 }}</ref>

=== Intelligence ===
{{Further|Handedness and mathematical ability|List of musicians who play left-handed}}
In his book ''Right-Hand, Left-Hand'', Chris McManus of [[University College London]] argues that the proportion of left-handers is increasing, and that an above-average quota of high achievers have been left-handed. He says that left-handers' brains are structured in a way that increases their range of abilities, and that the genes that determine left-handedness also govern development of the brain's language centers.<ref>{{cite web | url = http://www.righthandlefthand.com/ | first = Chris | last = McManus | name-list-style = vanc | title = Right-Hand, Left-Hand official website | archive-url = https://web.archive.org/web/20120504153055/http://www.righthandlefthand.com/ | archive-date=2012-05-04 | access-date = 1 June 2006 }}</ref>

Writing in ''[[Scientific American]]'', he states:
<blockquote>Studies in the U.K., U.S. and Australia have revealed that left-handed people differ from right-handers by only one IQ point, which is not noteworthy ... Left-handers' brains are structured differently from right-handers' in ways that can allow them to process language, spatial relations and emotions in more diverse and potentially creative ways. Also, a slightly larger number of left-handers than right-handers are especially gifted in music and math. A study of musicians in professional orchestras found a significantly greater proportion of talented left-handers, even among those who played instruments that seem designed for right-handers, such as violins. Similarly, studies of adolescents who took tests to assess mathematical giftedness found many more left-handers in the population.<ref>{{cite journal | first = Chris | last = McManus | name-list-style = vanc | date = 14 April 2012 | title = Is It True That Left-Handed People Are Smarter Than Right-Handed People? | journal = Scientific American Mind }}</ref></blockquote>

Left-handers are overrepresented among those with lower cognitive skills and mental impairments, with those with [[intellectual disability]] being roughly twice as likely to be left-handed, as well as generally lower cognitive and non-cognitive abilities amongst left-handed children.<ref name="Goodman 193–212">{{cite journal |last1=Goodman |first1=Joshua |title=The Wages of Sinistrality: Handedness, Brain Structure, and Human Capital Accumulation |journal=Journal of Economic Perspectives |date=1 November 2014 |volume=28 |issue=4 |pages=193–212 |doi=10.1257/jep.28.4.193 |doi-access=free }}</ref> Conversely, left-handers are also overrepresented in high IQ societies, such as [[Mensa International|Mensa]]. A 2005 study found that "approximately 20% of the members of Mensa are lefthanded, double the proportion in most general populations".<ref>{{cite journal |last1=Perelle |first1=Ira B. |last2=Ehrman |first2=Lee |title=On the Other Hand |journal=Behavior Genetics |date=May 2005 |volume=35 |issue=3 |pages=343–350 |doi=10.1007/s10519-005-3226-z |pmid=15864449 }}</ref>

Ghayas & Adil (2007) found that left-handers were significantly more likely to perform better on [[intelligence test]]s than right-handers and that right-handers also took more time to complete the tests.<ref>{{cite journal |last1=Ghayas |first1=Saba |first2=Adnan |last2=Adil |title=Effect of handedness on intelligence level of students |journal=Journal of the Indian Academy of Applied Psychology |volume=33 |issue=1 |date=2007 |pages=85–91 |url=https://www.researchgate.net/publication/233529472 }}</ref> In a systematic review and meta-analysis, Ntolka & Papadatou-Pastou (2018) found that right-handers had higher IQ scores, but that difference was negligible (about 1.5 points).<ref name="Ntolka & Papadatou-Pastou">{{cite journal | vauthors = Ntolka E, Papadatou-Pastou M | s2cid = 33792592 | title = Right-handers have negligibly higher IQ scores than left-handers: Systematic review and meta-analyses | journal = Neuroscience and Biobehavioral Reviews | volume = 84 | pages = 376–393 | date = January 2018 | pmid = 28826694 | doi = 10.1016/j.neubiorev.2017.08.007 }}</ref>

The prevalence of ''difficulties'' in left-right discrimination was investigated in a cohort of 2,720 adult members of [[Mensa International|Mensa]] and [[Intertel]] by Storfer.<ref name=":3">{{cite journal |last1=Storfer |first1=Miles D. |title=Problems in Left-Right Discrimination in a High-Iq Population |journal=Perceptual and Motor Skills |date=October 1995 |volume=81 |issue=2 |pages=491–497 |doi=10.1177/003151259508100226 |pmid=8570344 }}</ref> According to the study, 7.2% of the men and 18.8% of the women evaluated their left-right directional sense as poor or below average; moreover participants who were relatively ambidextrous experienced problems more frequently than did those who were more strongly left- or right-handed.<ref name=":3" /> The study also revealed an effect of age, with younger participants reporting more problems.<ref name=":3" />

==== Early childhood intelligence ====
Nelson, Campbell, and Michel studied infants and whether developing handedness during infancy correlated with language abilities in toddlers. In the article they assessed 38 infants and followed them through to 12 months and then again once they became toddlers from 18 to 24 months. They discovered that when a child developed a consistent use of their right or left hand during infancy (such as using the right hand to put the pacifier back in, or grasping random objects with the left hand), they were more likely to have superior language skills as a toddler. Children who became lateral later than infancy (i.e., when they were toddlers) showed normal development of language and had typical language scores. The researchers used [[Bayley scales of infant development|Bayley scales]] of infant and toddler development to assess the subjects.<ref name="Nelson_2014">{{cite journal | vauthors = Nelson EL, Campbell JM, Michel GF | title = Early handedness in infancy predicts language ability in toddlers | journal = Developmental Psychology | volume = 50 | issue = 3 | pages = 809–14 | date = March 2014 | pmid = 23855258 | pmc = 4059533 | doi = 10.1037/a0033803 }}</ref>

===Music===
In two studies, [[Diana Deutsch]] found that left-handers, particularly those with mixed-hand preference, performed significantly better than right-handers in musical memory tasks.<ref name="Deutsch1978">{{cite journal |last1=Deutsch |first1=D |title=Pitch memory: an advantage for the left-handed |journal=Science |date=3 February 1978 |volume=199 |issue=4328 |pages=559–560 |doi=10.1126/science.622558 |pmid=622558 |bibcode=1978Sci...199..559D |s2cid=2274951 }}</ref><ref name="Deutsch1980">{{cite book |doi=10.1016/B978-0-12-343150-9.50016-0 |chapter=Handedness and Memory for Tonal Pitch |title=Neuropsychology of Left-Handedness |year=1980 |last1=Deutsch |first1=Diana |pages=263–271 |isbn=978-0-12-343150-9 }}</ref> There are also handedness differences in perception of musical patterns. Left-handers as a group differ from right-handers, and are more heterogeneous than right-handers, in perception of certain stereo illusions, such as the [[octave illusion]], the [[scale illusion]], and the [[glissando illusion]].<ref name="Deutsch2019">
{{cite book | vauthors = Deutsch D | title = Musical Illusions and Phantom Words: How Music and Speech Unlock Mysteries of the Brain | year = 2019 | url = https://global.oup.com/academic/product/musical-illusions-and-phantom-words-9780190206833 | publisher = Oxford University Press | lccn = 2018051786 | author-link = Diana Deutsch | isbn = 9780190206833 }}{{page needed|date=November 2020}}
</ref>

===Health===
Studies have found a positive correlation between left-handedness and several specific physical and mental disorders and health problems, including:

*[[Low birth weight|Lower birth weight]] and complications at birth are positively correlated with left-handedness.<ref>{{cite journal |last1=Goodman |first1=Joshua |title=The Wages of Sinistrality: Handedness, Brain Structure, and Human Capital Accumulation |journal=Journal of Economic Perspectives |date=November 2014 |volume=28 |issue=4 |pages=193–212 |doi=10.1257/jep.28.4.193 }}</ref><ref>{{cite journal |last1=Kauko Heikkilä,a,1 Catharina E. M. Van Beijsterveldt,b Jari Haukka,c Matti Iivanainen,d,2 Aulikki Saari-Kemppainen,e |title=Triplets, birthweight, and handedness |journal=Proc Natl Acad Sci U S A |date=Jun 5, 2018 |volume=115 |issue=23 |pages=6076–6081 |doi=10.1073/pnas.1719567115 |doi-access=free |pmid=29760105 |pmc=6003315 |bibcode=2018PNAS..115.6076H }}</ref>
*A variety of neuropsychiatric and developmental disorders such as [[autism spectrum]],<ref>{{cite journal |title=Handedness in autism spectrum disorders and intellectually disabled children and adolescents - Contrasting caregivers' reports with assessments of hand preference |journal=Heliyon |date=2024 |doi=10.1016/j.heliyon.2024.e25935 |doi-access=free |pmid=38380041 |last1=Samadi |first1=S. A. |volume=10 |issue=4 |pages=e25935 |pmc=10877286 |bibcode=2024Heliy..1025935S }}</ref> [[bipolar disorder]], [[anxiety disorders]], [[schizophrenia]], and [[alcoholism]] have been associated with left- and mixed-handedness.<ref name="Ocklenburg"/><ref>{{cite journal | vauthors = Hirnstein M, Hugdahl K | title = Excess of non-right-handedness in schizophrenia: meta-analysis of gender effects and potential biases in handedness assessment | journal = The British Journal of Psychiatry | volume = 205 | issue = 4 | pages = 260–7 | date = October 2014 | pmid = 25274314 | doi = 10.1192/bjp.bp.113.137349 | doi-access = free | author-link2 = Kenneth Hugdahl }}</ref>
*A 2012 study showed that nearly 40% of children with [[cerebral palsy]] were left-handed,<ref>{{cite journal | vauthors = Lin KR, Prabhu V, Shah H, Kamath A, Joseph B | s2cid = 6972136 | title = Handedness in diplegic cerebral palsy | journal = Developmental Neurorehabilitation | volume = 15 | issue = 5 | pages = 386–9 | date = 2015 | pmid = 22758776 | doi = 10.3109/17518423.2012.696736 }}</ref> while another study demonstrated that left-handedness was associated with a 62% increased risk of [[Parkinson's disease]] in women, but not in men.<ref>{{cite journal | vauthors = Gardener H, Gao X, Chen H, Schwarzschild MA, Spiegelman D, Ascherio A | title = Prenatal and early life factors and risk of Parkinson's disease | journal = Movement Disorders | volume = 25 | issue = 11 | pages = 1560–7 | date = August 2010 | pmid = 20740569 | pmc = 3132935 | doi = 10.1002/mds.23339 }}</ref> Another study suggests that the risk of developing [[multiple sclerosis]] increases for left-handed women, but the effect is unknown for men at this point.<ref>{{cite journal | vauthors = Gardener H, Munger K, Chitnis T, Spiegelman D, Ascherio A | title = The relationship between handedness and risk of multiple sclerosis | journal = Multiple Sclerosis | volume = 15 | issue = 5 | pages = 587–92 | date = May 2009 | pmid = 19389750 | pmc = 2771381 | doi = 10.1177/1352458509102622 }}</ref> 
*Left-handed women may have a higher risk of [[breast cancer]] than right-handed women and the effect is greater in post-menopausal women.<ref>{{cite journal | vauthors = Fritschi L, Divitini M, Talbot-Smith A, Knuiman M | title = Left-handedness and risk of breast cancer | journal = British Journal of Cancer | volume = 97 | issue = 5 | pages = 686–7 | date = September 2007 | pmid = 17687338 | pmc = 2360366 | doi = 10.1038/sj.bjc.6603920 }}</ref>
*At least one study maintains that left-handers are more likely to suffer from [[heart disease]], and are more likely to have reduced longevity from [[cardiovascular]] causes.<ref>{{cite journal | vauthors = Hughes JR, Dorner E, Wind M | s2cid = 21369165 | title = Is the decreased longevity among left-handers related to an increase in heart disease? | journal = Clinical EEG and Neuroscience | volume = 39 | issue = 4 | pages = 182–4 | date = October 2008 | pmid = 19044215 | doi = 10.1177/155005940803900406 }}</ref>
*Left-handers may be more likely to suffer bone fractures.<ref>{{cite journal | vauthors = Luetters CM, Kelsey JL, Keegan TH, Quesenberry CP, Sidney S | s2cid = 32654176 | title = Left-handedness as a risk factor for fractures | journal = Osteoporosis International | volume = 14 | issue = 11 | pages = 918–22 | date = November 2003 | pmid = 14530828 | doi = 10.1007/s00198-003-1450-z }}</ref>
*Left-handers have a lower prevalence of [[arthritis]] and [[Ulcerative colitis|ulcer]].<ref>{{cite journal |last1=Wysocki |first1=C. J. |last2=McManus |first2=I. C. |title=Left-handers have a lower prevalence of arthritis and ulcer |journal=Laterality |date=March 2005 |volume=10 |issue=2 |pages=97–102 |doi=10.1080/13576500442000256 |pmid=15849026 |s2cid=34998957 }}</ref>
*One [[systematic review]] concluded, "Left-handers showed no systematic tendency to suffer from disorders of the immune system."<ref>{{cite web|url=https://www.psychologytoday.com/blog/brain-myths/201303/three-myths-and-three-facts-about-left-handers|title=Three Myths and Three Facts About Left-Handers|work=Psychology Today}}</ref>

As handedness is a highly heritable trait associated with various medical conditions, and because many of these conditions could have presented a Darwinian fitness challenge in ancestral populations, this indicates left-handedness may have previously been rarer than it currently is, due to natural selection. However, on average, left-handers have been found to have an advantage in fighting and competitive, interactive sports, which could have increased their reproductive success in ancestral populations.<ref>{{cite news|last1=Knight|first1=Will | name-list-style = vanc |title=Left-handers win in hand-to-hand combat|url=https://www.newscientist.com/article/dn6773-left-handers-win-in-hand-to-hand-combat/|access-date=27 October 2016|work=[[New Scientist]]|date=8 December 2004|archive-url=https://web.archive.org/web/20161027125658/https://www.newscientist.com/article/dn6773-left-handers-win-in-hand-to-hand-combat/|archive-date=27 October 2016|url-status=live}}</ref>

=== Income ===
In 2006, researchers from [[Lafayette College]] and [[Johns Hopkins University]] concluded that there was no statistically 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>{{cite web | last = Waldfogel | first = Joel | name-list-style = vanc | date = 15 August 2006 | url = http://www.slate.com/id/2147842 | title = Sinister and Rich: The evidence that lefties earn more | archive-url = https://web.archive.org/web/20100112084036/http://www.slate.com/id/2147842 | archive-date=2010-01-12 | work = [[Slate (magazine)|Slate]] }}</ref>

In a 2014 study published by the [[National Bureau of Economic Research]], [[Harvard University|Harvard]] economist Joshua Goodman finds that left-handed people earn 10 to 12 percent less over the course of their lives than right-handed people. Goodman attributes this disparity to higher rates of emotional and behavioral problems in left-handed people.<ref name="Goodman 193–212"/>

=== Sports ===
{{See also|Southpaw stance}}
[[File:Michael Vick, November 2006 (1).jpg|thumb|[[Michael Vick]], a left-handed [[American football]] [[quarterback]], winds up to throw the ball to his teammate.]]
Interactive sports such as table tennis, badminton and cricket have an overrepresentation of left-handedness, while non-interactive sports such as swimming show no overrepresentation. Smaller physical distance between participants increases the overrepresentation. In [[fencing]], about half the participants are left-handed.<ref name=AEP>{{cite book | vauthors = Widermann D, Barton RA, Hill RA | chapter = Evolutionary perspectives on sport and competition | chapter-url = https://books.google.com/books?id=I20uPfEjsNQC&pg=PA290 | veditors = Roberts SC | doi = 10.1093/acprof:oso/9780199586073.001.0001 | title = Applied Evolutionary Psychology | year = 2011 | publisher = Oxford University Press| isbn = 9780199586073 }}</ref> In tennis, 40% of the [[Seed (sports)#Tennis|seeded players]] are left-handed.<ref name=":4">{{Cite book |last1=Graham |first1=Douglas |url=https://books.google.com/books?id=vKQcD6-Fs58C |title=Ideation: The Birth and Death of Ideas |last2=Bachmann |first2=Thomas T. |date=2004-04-15 |publisher=John Wiley & Sons |isbn=978-0-471-47944-4 |pages=38 |language=en}}</ref> The term ''southpaw'' is sometimes used to refer to a left-handed individual, especially in [[baseball]] and [[boxing]].<ref>{{cite encyclopedia |date=June 2011 |title=southpaw, n. and adj. |dictionary=Oxford English Dictionary |publisher=Oxford University Press |url=https://www.oed.com/view/Entry/185300 |url-access=subscription |access-date=5 July 2020 |edition=3rd}}</ref> Some studies suggest that right handed male athletes tend to be statistically taller and heavier than left handed ones.<ref>{{cite journal |last1=Abel & Kruger |title=Lefties are still a little shorter |journal=Perceptual and Motor Skills |date=2007 |volume=104 |issue=2 |pages=405–406 |doi=10.2466/pms.104.2.405-406 |pmid=17566429|s2cid=28204534 }}</ref>

Other, sports-specific factors may [[Confounding|increase or decrease]] the advantage left-handers usually hold in one-on-one situations:
* In [[baseball]], a right-handed pitcher's [[curve ball]] will break away from a right-handed batter and towards a left-handed batter (batting left or right does not indicate left or right handedness). While studies of handedness show that only 10% of the general population is left-handed, the proportion of left-handed [[MLB]] players is closer to 39% of hitters and 28% of pitchers, according to 2012 data.<ref>{{cite web |last1=Peterson |first1=Dan | name-list-style = vanc |title=Righties vs Lefties - The Importance Of Handedness Training In Hitting |url=https://www.gamesensesports.com/knowledge/2017/3/17/righties-vs-lefties-the-importance-of-handedness-training-in-baseball-hitting |website=Game Sense Sports |date=17 March 2017 |access-date=3 April 2019 |archive-url=https://web.archive.org/web/20190403165517/https://www.gamesensesports.com/knowledge/2017/3/17/righties-vs-lefties-the-importance-of-handedness-training-in-baseball-hitting |archive-date=3 April 2019 |url-status=live }}</ref> Historical [[batting average (baseball)|batting averages]] show that left-handed batters have a slight advantage over right-handed batters when facing right-handed pitchers.<ref>{{cite web |url=https://www.baseball-reference.com/leagues/split.cgi?t=b&lg=MLB&year=2012#plato |title=2012 Major League Baseball Batting Splits |website=Baseball Reference |access-date=6 March 2013 |archive-url=https://web.archive.org/web/20150909022801/http://www.baseball-reference.com/leagues/split.cgi?t=b&lg=MLB&year=2012#plato |archive-date=9 September 2015 |url-status=live }}</ref> Because there are fewer left-handed pitchers than right-handed pitchers, left-handed batters have more opportunities to face right-handed pitchers than their right-handed counterparts have against left-handed pitchers.<ref>{{cite web |url=http://www.hardballtimes.com/main/article/the-advantage-of-batting-left-handed/ | first = John | last = Walsh | name-list-style = vanc |title=The advantage of batting left-handed | date = 15 November 2007 |publisher=hardballtimes.com |access-date=7 March 2013 |archive-url= https://web.archive.org/web/20130313221124/http://www.hardballtimes.com/main/article/the-advantage-of-batting-left-handed |archive-date=13 March 2013 |url-status=live }}</ref> Fifteen of the top twenty [[List of Major League Baseball career batting average leaders|career batting average leaders]] in [[Major League Baseball]] history have been posted by left-handed batters.<ref>{{cite web |url=https://www.baseball-reference.com/leaders/batting_avg_career.shtml |title=Career Leaders & Records for Batting Average |website=Baseball Reference |access-date=6 March 2013 |archive-url=https://web.archive.org/web/20130413224624/http://www.baseball-reference.com/leaders/batting_avg_career.shtml |archive-date=13 April 2013 |url-status=live }}</ref>
** Because a left-handed pitcher faces first base when he is in position to throw to the batter, whereas a right-handed pitcher has his back to first base, a left-handed pitcher has an advantage when attempting to [[pickoff|pick off]] baserunners at first base.<ref name="First Base Pickoffs for Lefty Pitchers">{{cite web |url=http://baseball.isport.com/baseball-guides/first-base-pickoffs-for-lefty-pitchers |title=First Base Pickoffs for Lefty Pitchers |publisher=isport.com |access-date=7 March 2013 |archive-url=https://web.archive.org/web/20130622212223/http://baseball.isport.com/baseball-guides/first-base-pickoffs-for-lefty-pitchers |archive-date=22 June 2013 |url-status=dead }}</ref>
** Defensively in baseball, left-handedness is considered an advantage for [[first basemen]] because they are better suited to fielding balls hit in the gap between first and second base, and because they do not have to pivot their body around before throwing the ball to another [[infielder]].<ref>{{cite news |url=https://www.nytimes.com/2009/03/29/sports/baseball/29score.html?_r=0 | last = Miller | first = Stuart | name-list-style = vanc |title=The Decline of Left-Handed First Basemen |newspaper=nytimes.com |access-date=7 March 2013 |date=29 March 2009 |archive-url=https://web.archive.org/web/20150926170156/http://www.nytimes.com/2009/03/29/sports/baseball/29score.html?_r=0 |archive-date=26 September 2015 |url-status=live }}</ref> For the same reason, the other infielder's positions are seen as being advantageous to right-handed throwers. Historically, there have been few left-handed catchers because of the perceived disadvantage a left-handed catcher would have in making the throw to third base, especially with a right-handed hitter at the plate.<ref name="Left Handed Catchers">{{cite web |url=http://bb_catchers.tripod.com/catchers/catchleft.htm |title=Left Handed Catchers |publisher=The Encyclopedia of Baseball Catchers |access-date=7 March 2013 |archive-url=https://web.archive.org/web/20120817090402/http://bb_catchers.tripod.com/catchers/catchleft.htm |archive-date=17 August 2012 |url-status=live }}</ref> A left-handed catcher would have a potentially more dangerous time tagging out a [[baserunner]] trying to score.<ref name="Left Handed Catchers" /> With the ball in the glove on the right hand, a left-handed catcher would have to turn his body to the left to tag a runner. In doing so, he can lose the opportunity to brace himself for an impending collision.<ref name="Left Handed Catchers" /> On the other hand, the Encyclopedia of Baseball Catchers states:<ref name="Left Handed Catchers" />
{{Blockquote
|text=One advantage is a left-handed catcher's ability to frame a right-handed pitcher's breaking balls. A right-handed catcher catches a right-hander's [[breaking ball]] across his body, with his glove moving out of the strike zone. A left-handed catcher would be able to catch the pitch moving into the strike zone and create a better target for the umpire.}}
* In [[four wall handball]], typical strategy is to play along the left wall forcing the opponent to use their left hand to counter the attack and playing into the strength of a left-handed competitor.
* In [[handball]], left-handed players have an advantage on the right side of the field when attacking, getting a better angle, and that defenders might be unused to them. Since few people are left-handed, there is a demand for such players.
* In [[water polo]], the centre forward position has an advantage in turning to shoot on net when rotating the reverse direction as expected by the centre of the opposition defence and gain an improved position to score. Left-handed drivers are usually on the right side of the field, because they can get better angles to pass the ball or shoot for goal.
* [[Ice hockey]] typically uses a strategy in which a [[defenceman (ice hockey)|defence pairing]] includes one left-handed and one right-handed defender. A disproportionately large number of ice hockey players of all positions, 62 percent, shoot left, although this does not necessarily indicate left-handedness.<ref>{{cite news|url=http://www.buffalohockeybeat.com/depleted-sabres-defense-thrives/|title=Depleted Sabres defense thrives|last=Hoppe|first=Bill| name-list-style = vanc |work=Buffalo Hockey Beat|publisher=Olean Times Herald|date=January 23, 2017|access-date=January 23, 2017|archive-url=https://web.archive.org/web/20181216031952/http://www.buffalohockeybeat.com/depleted-sabres-defense-thrives/|archive-date=December 16, 2018|url-status=live}}</ref>
* In [[American football]], the handedness of a [[quarterback]] affects blocking patterns on the [[offensive line]]. [[Tight end]]s, when only one is used, typically line up on the same side as the throwing hand of the quarterback, while the [[offensive tackle]] on the opposite hand, which protects the quarterback's "blind side", is typically the most valued member of the offensive line. Receivers also have to adapt to the opposite spin.<ref>{{cite news |last1=Greene |first1=Nick |title=Why Left-Handed Quarterbacks Are So Rare |url=https://slate.com/culture/2020/11/tua-tagovailoa-left-handed-quarterbacks-rare-nfl.html |access-date=5 November 2020 |work=[[Slate (magazine)|Slate]] |date=2 November 2020}}</ref> While uncommon, there have been several [[List of left-handed quarterbacks|notable left-handed quarterbacks]].
* In [[bowling]], the oil pattern used on the bowling lane [[bowling ball#Effect of lane characteristics on ball motion|breaks down]] faster the more times a ball is rolled down the lane. Bowlers must continually adjust their shots to compensate for the ball's change in rotation as the game or series is played and the oil is altered from its original pattern. A left-handed bowler competes on the opposite side of the lane from the right-handed bowler and therefore deals with less breakdown of the original oil placement. This means left-handed bowlers have to adjust their shot less frequently than right-handed bowlers in team events or qualifying rounds where there are possibly 4-10 people per set of two lanes. This can allow them to stay more consistent. However, this advantage is not present in bracket rounds and tournament finals where matches are 1v1 on a pair of lanes.

=== Sex ===
According to a meta-analysis of 144 studies, totaling 1,787,629 participants, the best estimate for the male to female [[odds ratio]] was 1.23, indicating that men are 23% more likely to be left-handed. For example, if the incidence of female left-handedness was 10%, then the incidence of male left-handedness would be approximately 12% (10% incidence of left-handedness among women multiplied by an odds ratio of 1:1.23 for women:men results in a 12.3% incidence of left-handedness among men).<ref name="Papadatou">{{cite journal | vauthors = Papadatou-Pastou M, Martin M, Munafò MR, Jones GV | title = Sex differences in left-handedness: a meta-analysis of 144 studies | journal = Psychological Bulletin | volume = 134 | issue = 5 | pages = 677–699 | date = September 2008 | pmid = 18729568 | doi = 10.1037/a0012814 }}</ref>{{clarify|date=January 2018}}

=== Sexuality and gender identity ===
{{Further|Handedness and sexual orientation}}
Some studies examining the relationship between handedness and sexual orientation have reported that a disproportionate minority of homosexual people exhibit left-handedness,<ref>{{cite journal | vauthors = Lalumière ML, Blanchard R, Zucker KJ | title = Sexual orientation and handedness in men and women: a meta-analysis | journal = Psychological Bulletin | volume = 126 | issue = 4 | pages = 575–92 | date = July 2000 | pmid = 10900997 | doi = 10.1037/0033-2909.126.4.575 }}</ref> though findings are mixed.<ref>{{cite journal | vauthors = Mustanski BS, Bailey JM, Kaspar S | s2cid = 29217315 | title = Dermatoglyphics, handedness, sex, and sexual orientation | journal = Archives of Sexual Behavior | volume = 31 | issue = 1 | pages = 113–22 | date = February 2002 | pmid = 11910784 | doi = 10.1023/A:1014039403752 }}</ref><ref>{{cite journal |last1=Williams |first1=Terrance J. |last2=Pepitone |first2=Michelle E. |last3=Christensen |first3=Scott E. |last4=Cooke |first4=Bradley M. |last5=Huberman |first5=Andrew D. |last6=Breedlove |first6=Nicholas J. |last7=Breedlove |first7=Tessa J. |last8=Jordan |first8=Cynthia L. |author9-link=Marc Breedlove |last9=Breedlove |first9=S. Marc |title=Finger-length ratios and sexual orientation |journal=Nature |date=March 2000 |volume=404 |issue=6777 |pages=455–456 |doi=10.1038/35006555 |pmid=10761903 |bibcode=2000Natur.404..455W |s2cid=205005405 }}</ref><ref>{{cite journal | vauthors = Schwartz G, Kim RM, Kolundzija AB, Rieger G, Sanders AR | s2cid = 24358057 | title = Biodemographic and physical correlates of sexual orientation in men | journal = Archives of Sexual Behavior | volume = 39 | issue = 1 | pages = 93–109 | date = February 2010 | pmid = 19387815 | doi = 10.1007/s10508-009-9499-1 }}</ref>

A 2001 study also found that people assigned male at birth whose [[gender identity]] did not align with their assigned sex, were more than twice as likely to be left-handed than a clinical [[control group]] (19.5% vs. 8.3%, respectively).<ref>{{cite journal | vauthors = Zucker KJ, Beaulieu N, Bradley SJ, Grimshaw GM, Wilcox A | s2cid = 4987839 | title = Handedness in boys with gender identity disorder | journal = Journal of Child Psychology and Psychiatry, and Allied Disciplines | volume = 42 | issue = 6 | pages = 767–76 | date = September 2001 | pmid = 11583249 | doi = 10.1111/1469-7610.00773 }}</ref>

[[Paraphilia]]s (atypical sexual interests) have also been linked to higher rates of left-handedness. A 2008 study analyzing the sexual fantasies of 200 males found "elevated paraphilic interests were correlated with elevated non-right handedness".<ref>{{cite journal | vauthors = Rahman Q, Symeonides DJ | s2cid = 22274418 | title = Neurodevelopmental correlates of paraphilic sexual interests in men | journal = Archives of Sexual Behavior | volume = 37 | issue = 1 | pages = 166–72 | date = February 2008 | pmid = 18074220 | doi = 10.1007/s10508-007-9255-3 }}</ref> Greater rates of left-handedness have also been documented among [[pedophilia|pedophiles]].<ref>{{cite journal | vauthors = Blanchard R, Kolla NJ, Cantor JM, Klassen PE, Dickey R, Kuban ME, Blak T | s2cid = 220359453 | title = IQ, handedness, and pedophilia in adult male patients stratified by referral source | journal = Sexual Abuse | volume = 19 | issue = 3 | pages = 285–309 | date = September 2007 | pmid = 17634757 | doi = 10.1177/107906320701900307 }}</ref><ref>{{cite journal | vauthors = Cantor JM, Klassen PE, Dickey R, Christensen BK, Kuban ME, Blak T, Williams NS, Blanchard R | s2cid = 6427342 | display-authors = 6 | title = Handedness in pedophilia and hebephilia | journal = Archives of Sexual Behavior | volume = 34 | issue = 4 | pages = 447–59 | date = August 2005 | pmid = 16010467 | doi = 10.1007/s10508-005-4344-7 }}</ref><ref>{{cite journal | vauthors = Bogaert AF | s2cid = 28513717 | title = Handedness, criminality, and sexual offending | journal = Neuropsychologia | volume = 39 | issue = 5 | pages = 465–9 | year = 2001 | pmid = 11254928 | doi = 10.1016/S0028-3932(00)00134-2 }}</ref><ref>{{cite journal | vauthors = Dyshniku F, Murray ME, Fazio RL, Lykins AD, Cantor JM | s2cid = 25667170 | title = Minor Physical Anomalies as a Window into the Prenatal Origins of Pedophilia | journal = Archives of Sexual Behavior | volume = 44 | issue = 8 | pages = 2151–9 | date = November 2015 | pmid = 26058490 | doi = 10.1007/s10508-015-0564-7 }}</ref>

A 2014 study attempting to analyze the biological markers of [[asexuality]] asserts that non-sexual men and women were 2.4 and 2.5 times, respectively, more likely to be left-handed than their heterosexual counterparts.<ref name=Yule>{{cite journal | vauthors = Yule MA, Brotto LA, Gorzalka BB | s2cid = 5347734 | title = Biological markers of asexuality: Handedness, birth order, and finger length ratios in self-identified asexual men and women | journal = Archives of Sexual Behavior | volume = 43 | issue = 2 | pages = 299–310 | date = February 2014 | pmid = 24045903 | doi = 10.1007/s10508-013-0175-0 }}</ref>

=== Mortality rates in combat ===
A study at [[Durham University]]—which examined mortality data for [[cricketers]] whose handedness was a matter of public record—found that left-handed men were almost twice as likely to die in war as their right-handed contemporaries.<ref>{{cite journal | vauthors = Aggleton JP, Kentridge RW, Neave NJ | title = Evidence for longevity differences between left handed and right handed men: an archival study of cricketers | journal = Journal of Epidemiology and Community Health | volume = 47 | issue = 3 | pages = 206–9 | date = June 1993 | pmid = 8350033 | pmc = 1059767 | doi = 10.1136/jech.47.3.206 }}</ref> The study theorised that this was because weapons and other equipment was designed for the right-handed. "I can sympathise with all those left-handed cricketers who have gone to an early grave trying desperately to shoot straight with a right-handed Lee Enfield .303", wrote a journalist reviewing the study in the cricket press.<ref>{{Cite journal|last=Jonathan|first=Rice| name-list-style = vanc |date=February 1995|title=Left For Dead|journal=Wisden Cricket Monthly}}</ref> The findings echo those of previous American studies, which found that left-handed US sailors were 34% more likely to have a serious accident than their right-handed counterparts.<ref>{{cite web |url= https://www.newscientist.com/article/mg14119163-000-science-sudden-death-for-left-handers/ |title=Science: Sudden death for left-handers|last= Brown |first = William | name-list-style = vanc |website=New Scientist|language=en-US|access-date=2020-02-01}}</ref>

===Episodic memory===
A high level of handedness (whether strongly favoring right or left) is associated with poorer [[episodic memory]],<ref>{{cite journal | vauthors = Propper RE, Christman SD, Phaneuf KA | s2cid = 2989930 | title = A mixed-handed advantage in episodic memory: a possible role of interhemispheric interaction | journal = Memory & Cognition | volume = 33 | issue = 4 | pages = 751–7 | date = June 2005 | pmid = 16248339 | doi = 10.3758/BF03195341 }}</ref><ref>{{cite journal | vauthors = Sahu A, Christman SD, Propper RE | title = The contributions of handedness and working memory to episodic memory | journal = Memory & Cognition | volume = 44 | issue = 8 | pages = 1149–1156 | date = November 2016 | pmid = 27259533 | doi = 10.3758/s13421-016-0625-8 | doi-access = free }}</ref> and with poorer communication between brain hemispheres,<ref>{{cite journal | vauthors = Prichard E, Propper RE, Christman SD | title = Degree of Handedness, but not Direction, is a Systematic Predictor of Cognitive Performance | language = en | journal = Frontiers in Psychology | volume = 4 | pages = 9 | date = 2013 | pmid = 23386836 | doi = 10.3389/fpsyg.2013.00009 | pmc = 3560368 | doi-access = free }}</ref> which may give poorer emotional processing, although [[bilateral stimulation]] may reduce such effects.<ref>{{cite journal | vauthors = Shobe ER | title = Independent and collaborative contributions of the cerebral hemispheres to emotional processing | journal = Frontiers in Human Neuroscience | volume = 8 | pages = 230 | date = 2014-04-22 | pmid = 24795597 | pmc = 4001044 | doi = 10.3389/fnhum.2014.00230 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Spielberg JM, Heller W, Miller GA | title = Hierarchical brain networks active in approach and avoidance goal pursuit | journal = Frontiers in Human Neuroscience | volume = 7 | pages = 284 | date = 2013-06-17 | pmid = 23785328 | pmc = 3684100 | doi = 10.3389/fnhum.2013.00284 | doi-access = free }}</ref>

=== Corpus callosum ===
A high level of handedness is associated with a smaller [[corpus callosum]] whereas low handedness with a larger one.<ref>{{cite journal |last1=Luders |first1=Eileen |last2=Cherbuin |first2=Nicolas |last3=Thompson |first3=Paul M. |last4=Gutman |first4=Boris |last5=Anstey |first5=Kaarin J. |last6=Sachdev |first6=Perminder |last7=Toga |first7=Arthur W. |title=When more is less: Associations between corpus callosum size and handedness lateralization |journal=NeuroImage |date=August 2010 |volume=52 |issue=1 |pages=43–49 |doi=10.1016/j.neuroimage.2010.04.016 |pmid=20394828 |pmc=2903194 }}</ref>

=== Divergent thinking ===
Left-handedness is associated with better [[divergent thinking]].<ref>{{Cite journal |last=Coren |first=Stanley |date=1995 |title=Differences in Divergent Thinking as a Function of Handedness and Sex |journal=The American Journal of Psychology |volume=108 |issue=3 |pages=311–325 |doi=10.2307/1422892 |jstor=1422892 |pmid=7573608 }}</ref>