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In this hebdomadary series , LiveScience examines the psychology and sociology of opposite human behavior and personality type .
To get a sense of human handedness , take a survey of those combination chair - desk piece of furniture pieces in schoolroom . The screen background be given to wrap around from the right . That ’s so right - handers can well rest their arm while jotting down musical note with their predominant hand . For that rare left - hander , if he or she is lucky , there might be an odd - looking desk or two with an oppositely molded desktop .
Whether you’re a righty or lefty may say more about you than what hand you use to write or play sports.
Such classroom jingoism reflects the puzzlingly secure prejudice towardright - hand dominancein our metal money . All over the satellite , nine out of 10 masses , on average , favor their veracious hand for writing , throwing and so on . ( " Footedness " roughly follow this same breakdown , though for sensory electric organ , such as eye and ears , druthers is less skewed;true ambidexterityoccurs in less than 1 per centum of the population . )
Despite more than a century and a half of research , scientists have yet to find an result for what causes laterality . " It ’s a very good question but we do n’t know , " order David P. Carey , a neuropsychologist at Bangor University in the U.K.
Clues relating to asymmetry in our soundbox , and especially in the brain , however , could help explain the paucity of " south paw . "
Are you a righty or a lefty?
To the left , to the right
The pick of one script for fine motor control might excogitate the fact that much of our anatomy and function is not balanced .
Our internal organs do not mirror the consistency ’s outside , bilateral symmetricalness — that pattern of two opposing leg , deal , nipple , eyes , ear and so on . The tenderness and lien , for example , normally shape on the body ’s left side , the liver on the right ; each lung bears a distinctly dissimilar shape .
And so it goes with our brainiac . That wrinkly pulp in our skull divide down the midriff into two hemispheres and , in a quirk of evolution , each hemisphere controls the diametric side of the body ; that is , the brain ’s left hemisphere operates our correct side , and vice versa . The same outgrowth occurs with visual sensation — what our left eye " sees " is process by the right rear of the brain . [ 10 thing You Did n’t have sex About the Einstein ]
Although the two halves of our brain have generally similar anatomy , sure tasks run to be plow by one side of the nous more than the other . scientist chalk this up to efficiency ’s rice beer , as performing matching , co-occurrent action on each side blow vim and available encephalon power .
" For a good deal of actions , it ’s a good idea to have the genus Bos living in one place , " Carey enounce .
Hand to mouth
That phenomenon ofbrain laterality and division of laborcould help explain handedness . Among the more demanding and latterly evolved tasks for our learning ability is terminology processing and generation . Intriguingly , in 90 percent to 95 percent of right - handers , the left cerebral hemisphere is dominant for language and language function , suggesting organic evolution has honed one side to handle skillful work .
" If I have one part of my brain controlling my fine motor movements , it would make sense to have this part handle speech , too , " Carey told LiveScience .
Yet the kinship is not so simple-minded . About two - third of lefthander are also left - hemisphere rife for words and language , Carey enounce , and some 5 percent or more of righties have right - cerebral hemisphere ascendency . [ Constant Battle as psyche pock ripe bridge player Against Left ]
turn over into genetic science has not yet explained away the extreme bias toward human rightfulness - handedness either , though mite of inheritance egress . The luck of two left-hand - handed parents take left - handed offspring , for instance , is around 25 per centum , compared with 10 percent in the general universe . A gene hear in 2007 , call LRRTM1 , designate up more in left hander as well .
Paws to claws
research worker have also look to other creature to help them solve thehuman riddle of handedness . Many mammalian , including our close living congenator the chimp , Pan paniscus and gorillas , parade a preferred hand . So , too , do dogs .
" Your dog is one - paw , " said Carey . " If you force a dog to reach for a miniature through an aperture , it will tend over many trials to habituate one paw over the other . "
But this breakdown for unexpended versus right in Fido as well as Coco is about 50 - 50 , eschewing humans ' overpoweringly right - sided universe - handedness . That even - handed , if you will , break run to non - mammal such as fiddler crabs , whose magnified hook for campaign develops on either side in equal bill .
" Sinister " left-handed pitcher ?
Whatever laterality ' ancestry in humankind , it ’s clearly been around a long meter . For example , cave painting have shown the episodic lefty ascendent clutching a spear .
The relative scarcity of left-hand - laterality , as with many " otherisms " inhuman history , has provoked cultural superstition and discrimination . Even just several decade ago in the U.S. , parents and teacher still snatched pencil out of baby ’s unexpended hand and tried making lefties write like a righty .
The ancient prejudice against lefties remains embedded in the English language . " Sinister " partake in a Latin root with " sinistral , " meaning " in regards to the unexpended side , " and " go out " derives from the Anglo - Saxon word for " weak . "
For biologic reasons yet strange , lefties might indeed be more or less cursed . That cistron associated with left - handedness , LRRTM1 , is also associated with the genial disease dementia praecox . Correlations have been found for left - handedness and illnesses such as incitive gut disease and alcoholism .
On the other helping hand , some evidence indicate tolefties possess on modal more intelligenceor artistic giftedness than righties , perhaps given their alternative mind . Interestingly , four out of the last seven presidents have been left - handers , include Barack Obama , Bill Clinton , George H.W. Bush and Gerald Ford .
Living as a left-hander
Overall , handedness — inasmuch as it offers insight into an person ’s intellectual and bodily ability , leaning and deficits — is just one of many elements in a complicated picture .
" There is not a one - to - one coefficient of correlation . … . It is not as if you are depart - handed [ so ] you will become glorious or get a disease , " said Amar Klar , a geneticist at the National Cancer Institute ’s Center for Cancer Research in Frederick , Md.
Although the stain against left - handedness has largely lifted around the earth , Carey pointed out that righties still have it leisurely .
" Poor lefties have to live in a right - handed world , " Carey told LiveScience . " The tent-fly in your trousers is decently - handed ; even a can opener is right - handed . "
