WHY SOME PEOPLE ARE LEFT HANDED?
Do you know Worlds
90% population is right handed and 10% is left handed.
Ever thought what is the issue with this handedness? Why are some left handed and why some are right handed?
Let us first discuss what handedness is, in human biology handedness refer to dominant hand i.e. which hand an individual prefers or is capable for performing tasks with more efficient way.
Well, some say its evolution (because most the instruments including very basic one ‘scissor’ to the tool one can date back to centuries that primitive Homo sapiens used.), But some say this decided in genetics of a person(from the time when a baby is in womb of mother it decides which thumb it will love to suck).
Some research studies of prenatal development lead to the belief that handedness is
determined in womb. After birth, 39% of
infants (6 to 14 months) 97% of
toddlers (18 to 24 months) demonstrated
hand preference.
Let’s get into each of commonly considered causes:
DIVISION OF
LABOUR:
Our cerebral hemispheres are divided into regions for doing certain activities according to a common theory. E.g. speaking and handiwork if are assigned to left side, the person will turn out be right handed and left handed will have reversed division of labor.
GENETIC FACTOR:
Genetics says about a complex inheritance pattern saying that if both parents are left handed there are 26% chances of their child to be left handed.
EPIGENETIC FACTORS:
In simple words change
in DNA during fetal development cause left handedness.
(In scientific words TWIN
THEORY indicates that genetic factors explain 25% of the variance in
handedness, while environmental factors explain the remaining 75%. While
the molecular basis of handedness EPIGENETICS is largely unclear,
Ocklenburg et al. 2017 found that asymmetric METHYLATION of CpG SITES plays
a key role for GENE EXPRESSION asymmetries that have been related to
handedness.)
THE WAY BABY IS IN
WOMB (PRENATAL VESTIBULAR ASYMMETRY)
Evidence found that positioning of fetus in final trimester and baby’s subsequent birth position of can affect handedness. Scientist also tried answering premature birth leading to decrease in right handedness.
ULTRASOUND
Another theory suggested ultrasound sometimes alters the brain of unborn children, causing higher rates of left handedness in child whose mother was subject to ultrasounds.
Development time
Children right from very beginning told to hold objects
from right hand making as significant effect as 75% effect to shape which hand
becomes their dominant hand. The decrease in
handedness variability for 36-to-48-month-old children could likely be
attributed to preschool or kindergarten attendance.
Scharoun and Bryden noted that right-handed preference increases with age up to the teenage years.
Ever heard a kid was left handed but turned into right handed during kindergarten, a children is subjected to sometimes forced handling of objects trying to make hold certain things like pencil, crayons and objects just to alter handedness making right handed dominant and may end up child becoming right handed up to some extent.
IN CULTURE:
Main article: Bias against left-handed people
Many tools and procedures are designed to facilitate use by
right-handed people, often without realizing the difficulties incurred by the
left-handed. John W. Santrock has written, "For centuries, left-handers
have suffered unfair discrimination in a world designed for
right-handers."
It is not scissors only that people have made for right handed
people, look in market you will see every other tool working with majority of
market i.e. right handed people .
Why?
Answer is profit.
This has sometimes lead to serious injuries including
amputations of hands of people working in industries.
Why?
Because those machines were made to work for right handed people only.
CORRELATION OF
INTELLIGENCE WITH LEFT HANDEDNESS
In his book Right-Hand,
Left-Hand, 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 centers of the brain.
Writing in Scientific American, McManus states that,
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.
Conversely, Joshua
Goodman found that evidence for left-handers being overrepresented amongst high
end of the cognitive spectrum was weak due to methodological and sampling
issues in conducted studies. In simple words sample size of left handed people
is less as they constitute only ten percent population.
So, considering that
in general left handed people have high cognitive ability is still an idea that
doesn’t fit some scientist well.
International Left-Handers Day
Main article: International Left-Handers Day
International
Left-Handers Day is held annually every August 13. It was founded
by the Left-Handers Club in 1992, with the club itself having been founded in
1990.
International Left-Handers Day is,
according to the club, "an annual event when left-handers everywhere can
celebrate their sinistrality (left-handedness) and increase public awareness of
the advantages and disadvantages of being left-handed."
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Your content is nice . I was a left hand person but my mind was trained to be a right hand person now I do some of work with left or rest with right 🧐🤔so can u explain that either I have tht speciality that left person have or not if now I m not a left hand person 🧐
ReplyDeleteYou might be trained to do some physical work which is visible to everyone out there but your brain will still use your dominant hand to do other tasks and your cerebral hemispheres might work in same way as other left handed ones, considering the epigenetic factors theory most acceptable, I would rather say that your DNA has don this left handed things which can not be changed by training in any environment so you will be considered "ambidextrous" that mean who can use both hands to do tasks after training.
DeleteOhh that's grt to know I m still special 🤣🤣
DeleteWell girl nice content and nice reply I m impressed
Thank you:)
DeleteGreat
ReplyDeleteThank you:)
Delete