The brains and bodies of lefties work differently from those of right-handed or left- and right-handed people with the same precision, or who rely on using each hand separately to perform different tasks, according to CNN.
Being left-handed is determined very early in the development process as a fetus in the mother’s womb, says Professor Ronald Yu, professor of psychology at the University of Texas-Austin, and it has many implications for health.
Yu says scientists aren’t quite sure why some people are left-handed, but they do know that genetics is responsible for only 25% of left-handed people’s tendency to be left-handed, which is significantly less than other inherited traits, such as height or intelligence. He adds that in some cases of identical twins who share the same genes, sometimes the dominant hands are different. There are plenty of theories about other things that could determine which hand a person writes with, but many experts believe it’s somewhat random.
stress during pregnancy
In one 2008 Swedish study of mothers and their 5-year-old children, women who were depressed or stressed during pregnancy were more likely to have mixed or dyslexic children. In other studies, a baby with a low birth weight, or an older mother, was also more likely to be left-handed.
A non-left-handed person uses the left hemisphere to process language, but that doesn’t mean that most left-handers use their right hemisphere, says Professor Gina Grimshaw, director of the cognitive and affective neuroscience lab at the University of Wellington in New Zealand. It’s just a common myth.
She adds that about 98% of right-handed users are left-handed as well, while the percentage is not more than about 70% among left-handed users, noting that only about 30% are right-brained or bi-brained, that is, they have equal Capacity both halves of the brain. “It appears that most left-handers have similar language processing to right-handers,” says Professor Grimshaw. For other unilateral brain functions, such as attention, emotion, music and facial perception, there is less data.
Left-handedness can affect school performance. A 2009 Australian study of children aged 11 or younger found that left-handed children performed worse on many measures, such as vocabulary, reading and writing, social development and gross motor skills. While the performance of children who used mixed hands worse than the performance of left-handers. The researchers suggest that mixed- and left-handed children use both halves of their brains unusually.
Professor Yu says the reason may be because, for example, some mixed-handed children are confused about which hand to write with, but he points out that in both cases, most children catch up with their classmates as they get older, so whether a student is left-handed or mixed-handed is not an indicator Definitely how well he’s doing as he grows.
mental health problems
Left-handers can be more likely to develop psychotic disorders such as schizophrenia than right-handers or both hands, according to a 2013 Yale University study. When researchers surveyed patients in a mental health clinic, 40% of people with schizophrenia or schizophrenia said they were left-handed, while left-handers were more likely to develop psychotic disorders such as schizophrenia. Other studies have found a link between lack of right-handedness, dyslexia, ADHD, and some other mood disorders.
Most experts agree that the left-handed athlete stands out from the rest, especially in individual sports such as tennis, boxing, and baseball. In a French study conducted in 2005, researchers concluded that a left-handed person has a physical advantage over a right-handed or right-footed user and is based on the element of sudden or unexpected movement.
Breast cancer risk
Left-handed use appears to be associated with some physical health issues. In a 2007 study published in the British Journal of Cancer, researchers reported that left-handed women have a higher risk of breast cancer than right-handers, especially for postmenopausal cancers.
Scientists have long suspected that left-handed use is somehow linked to immune function, and that it may be a risk factor for an autoimmune disorder. Professor Grimshaw says that scientific research has not been able to support most of these claims, and this theory has been largely refuted.
Some sleep problems
In a 2011 survey conducted by the University of Toledo of 100 patients in a sleep clinic, researchers discovered that 69% of right-handed users experienced side limb movements while sleeping, while the percentage rose to 94% among left-handed patients, which means that Left handers are significantly more likely to develop PLMD related to bilateral limb movements.
The results of a 2007 Scottish study reported that left-handed people were more likely to show symptoms of PTSD after watching clips from a scary movie, and that they experienced more negative emotions. Both conclusions could be due to the fact that left-handers are more likely to have their brains process fear and anger differently.
“Hopefully we will have a better understanding,” Professor Grimshaw says [للعٌسر] Soon.” One thing for sure, Professor Yu said, is that “we shouldn’t assume much about people’s character or health just because they write with their right or left hand. And we certainly shouldn’t worry about a left-handed person’s chances of success, because for example, until 2015 five of the last seven US presidents were left-handed or mixed-handed.
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