03-14 16:08:17 | www.jiaoxue51.com | 雅思考试 | 人气:149次
雅思阅读考试模拟试题一例是关于 雅思考试,方面的资料,本站还有更多关于雅思真题,雅思阅读,雅思作文,雅思口语话题,雅思机经,雅思试题方面的资料,http://www.jiaoxue51.com。
Right and left-handedness in humans
Why do humans, virtually alone among all animal species, display a distinct left or right handedness? Not even our closest relatives among the apes possess such decided lateral asymmetry, as psychologists call it. Yet about 90 per cent of every human population that has ever lived appears to have been right-handed. Professor Bryan Turner at Deakin University has studied the research literature on left-handedness and found that handedness goes with sidedness. So nine out of ten people are right-handed and eight are right-footed. He noted that this distinctive asymmetry in the human population is itself systematic. `Humans think in categories: black and white, up and down, left and right. It’s a system of signs that enables us to categorise phenomena that are essentially ambiguous.’
Research has shown that there is genetic or inherited element to handedness. But while left-handedness tends to run in families, neither left nor right handers will automatically produce off-spring with the same handedness; in fact about 6 per cent of children with two right-handed parents will be left-handed. However, among two left-handed parents, perhaps 40 per cent of the children will also be left-handed. With one right and one left-handed parent, 15 to 20 per cent of the offspring will be lefthanded. Even among identical twins who have exactly the same genes, one in six pairs will differ in their handedness.
What then makes people left-handed if it is not simply genetic? Other factors must be at work and researchers have turned to the brain for clues. In the 1860s the French surgeon and anthropologist, Dr Paul Broca, made the remarkable finding that patients who had lost their powers of speech as a result of a stroke (a blood clot in the brain) had paralysis of the right half of their body. He noted that since the left hemisphere of the brain controls the right half of the body, and vice versa, the brain damage must have been in the brain’s left hemisphere, Psychologists now believe that among right handed people, probably 95 per cent have their language centre in the left hemisphere, while 5 per cent have right-sided language, Left-handers, however,do not show the reverse pattern but instead a majority also Some 30 per cent have right hemisphere language.
Dr Brinkman, a brain researcher at the Australian National University in Canberra, has suggested that evolution of speech went with right-handed preference. According to Brinkman, as the brain evolved, one side became specialised for fine control of movement (necessary for producing speech) and along with this evolution came righthand preference. According to Brinkman, most left-handers have left hemisphere dominance but also some capacity in the right hemisphere. She has observed that if a left-handed person is brain-damaged
o left-handers who have for centuries lived in a world designed to suit right-handed people. However, what is alarming, according to Mr. Charles Moore, a writer and journalist, is the way the word `right’ reinforces its own virtue. Subliminally he says, language tells people to think that anything on the right can be trusted while anything on the left is dangerous or even sinister. We speak of left-handed compliments and according to Moore, `it is no coincidence that left-hand, often develop a stammer as they are robbed of their freedom of speech’. However, as more research is undertaken on the causes of left handedness, attitudes towards left-handed people are gradually changing for the better. Indeed when the champion tennis player Indeed when the champion tennis player Ivan Lendl was asked what the single thing improve his game, he said he would like to become a left-ha, www.jiaoxue51.comnder.
与雅思阅读考试模拟试题一例相关的推荐
相关分类
最新资料
雅思考试推荐