Right And Left Handedness In Humans Reading Passage
Right And Left Handedness In Humans Reading Passage
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Why do humans, who are essentially the only left- or right-handed animal species, exhibit this trait? Such clear lateral asymmetry, as psychologists refer to it, is not even present in our nearest ancestors among the apes. Yet, it appears that 90% of all human populations throughout history have been right-handed. After reviewing the evidence on left-handedness, Professor Bryan Turner from Deakin University discovered that handedness and sidedness go hand in hand. Hence, eight out of ten persons are right-footed, and nine out of ten are right-handed. In the human population, he observed, there is a distinctive asymmetry that is itself systematic. “Left and right, up and down, and black and white in such a way humans categorise their thoughts into.” We can group things that are essentially unclear using this collection of signals.
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According to research, handedness has a genetic or inherited component. Despite the notion that left-handedness typically runs in families, neither left nor right-handed adults are guaranteed to give birth to children who share their handedness; in fact, only about 6% of children with two right-handed parents are left-handed. Yet, if both parents are left-handed, then maybe 40% of the offspring will be left-handed as well. 15% to 20% of the offspring will be left-handed if both parents are right-handed. One in six pairs of identical twins who share the same genes will have different handedness.
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If it is not just genetic, what causes people to be left-handed? Researchers are looking to the brain for hints as to what additional elements might be at play. Dr. Paul Broca, a French physician and anthropologist, discovered in the 1860s that stroke victims who lost their ability to speak as a result of a blood clot in the brain also experienced right-side paralysis. As the right half of the body is controlled by the left hemisphere of the brain and the left hemisphere by the right, he recognised that the left hemisphere of the brain must have sustained injury. Today, psychologists estimate that 95% of right-handed people have their language centres in the left hemisphere, compared to 5% who have right-sided language. However, left-handed people do not exhibit the opposite tendency; rather, the majority also speak from their left hemisphere. 30% of people speak a language from their right hemisphere.
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Dr. Brinkman, a neurological scientist at Australia's National University in Canberra, hypothesises that the evolution of speech corresponded to a preference for utilising one's right hand. Brinkman claims that as the brain changed through time, one side grew more adept at precise movement, which is required for speaking, and this change resulted in a preference for the right hand. Brinkman asserts that although most left-handers have a predominance in the left hemisphere, they still have some aptitude in the right hemisphere. Because left-handers have a more bilateral speaking function, she has noticed that when a left-handed individual has brain damage in the left hemisphere, speech recovery is frequently better.
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According to Brinkman's research on macaque monkeys, primates (monkeys) appear to learn a preference for one or both hands from their mothers during the first year of life. However, in humans, the two hemispheres' functional specialisation leads to physical differences: regions involved in speech production are typically larger on the left side than on the right. One would not anticipate seeing such a variation in monkeys as they have not yet mastered the ability of speech, but Brinkman claims to have found a pattern in monkeys that is similar to the asymmetry found in the human brain.
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Geschwind and Galaburda, two American scientists who examined the brains of developing human beings, found that the left-right asymmetry already occurs before birth. However, a variety of factors can impact how the brain grows. Every brain has a feminine organisational structure at first; it only changes to a masculine structure when the male embryo starts to emit hormones. Geschwind and Galaburda were aware that the right and left hemispheres of the brain develop at distinct rates of maturation. Additionally, a girl's brain matures a little bit quicker than a boy's. Therefore, males are more vulnerable to experiencing problems with the development of their brains during pregnancy, and the left hemisphere is more likely to be involved. Left-handedness and the development of certain superior skills that have their roots in the left hemisphere, such as logic, rationality, and abstraction, may arise from the brain being less lateralised. Therefore, it should come as no surprise that there are more left-handed men than women in the fields of mathematics and architecture.
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The findings of this study may provide some relief to left-handed persons who have spent decades adjusting to a world that was made for right-handed people. But what worries writer and journalist Mr. Charles Moore is the way the term "right" maintains its own goodness. Language, according to him, subtly instructs people to believe that everything on the right is safe to trust, while anything on the left is untrustworthy or even evil. When it comes to left-handed compliments, Moore claims that "it is no mystery that left-handed children who are compelled to utilise their right hand often acquire stammering as they are stripped of their right of speech." However, attitudes towards left-handed people are gradually improving as more research is done on the factors that contribute to the condition. In fact, when asked what one change he would make to his game, tennis champion Ivan Lendl replied that he would like to switch from being a righthander to a lefthander.
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