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  3. Left-handers have been the subject of curiosity, stigma and even fear over the centuries. Researchers now, however, are recogniz

Left-handers have been the subject of curiosity, stigma and even fear over the centuries. Researchers now, however, are recogniz

admin2014-09-30  44
问题     Left-handers have been the subject of curiosity, stigma and even fear over the centuries. Researchers now, however, are recognizing the scientific importance of understanding why people use one hand or the other to write, eat or toss a ball.
    Handedness, as the dominance of one hand over the other is called, provides a window into the way our brains are wired, experts say. And it may help shed light on disorders related to brain development, like dyslexia(诵读困难症), schizophrenia(精神分裂症)and attention deficit hyperactivity disorder, or ADHD(注意力缺陷多动障碍), which are more common in left-handed people.
    Other recent research suggests that mixed-handedness—using different hands for daily tasks and not having a dominant one—may be even more strongly linked than left-handedness to ADHD and possibly other conditions.
    About 10% of people are left-handed, according to expert estimates. Another 1% of the population is mixed-handed. What causes people not to favor their right hand is only partly due to genetics—even identical twins, who have 100% of the same genes, don’t always share handedness.
    More important, researchers say, are environmental factors—especially stress—in the womb. Babies born to older mothers or at a lower birth weight are more likely to be lefties, for example. And mothers who were exposed to unusually high levels of stress during pregnancy are more likely to give birth to a left-handed child. A review of research, published in 2009 in the journal Neuropsychologia, estimated that about 25% of the variability in handedness is due to genetics.
    On average there is no significant difference in IQ between righties and lefties, studies show, betraying popular perceptions. There is some evidence that lefties are better at divergent thinking, or starting from existing knowledge to develop new concepts, which is considered an element of creativity. And left-handed people have salaries that on average are about 10% lower than righties, according to recent research performed at Harvard University that analyzed large income data bases, although findings of some earlier studies were mixed.
    Left-handedness appears to be associated with a greater risk for a number of psychiatric and developmental disorders. While lefties make up about 10% of the overall population, about 20% of people with schizophrenia are lefties, for example. Links between left-handedness and dyslexia, ADHD and some mood disorders have also been reported in research studies.
    The reasons for this aren’t clear. Scientists speculate it could be related to a concept known as brain lateralization. The brain has two halves. Each performs primarily separate, specialized functions, such as language processing, which mainly takes place in the left hemisphere. There is lots of communication between the hemispheres.
What is the most possible reason for left-handedness?
选项 A、The living environment of left-handers is highly stressful.
B、Left-handedness is more likely to be affected by genetics.
C、Mothers might be under high stress when they were in pregnancy.
D、Mothers might lose weight when they gave birth.
答案C
解析 细节推断题。第四段第三句中的causes和due to表明本句的内容是有关偏手性的原因，基因是造成偏手性的部分原因。第五段第一句紧接着指出了更重要的原因(More important…factors)与子宫环境有关：年龄较大的母亲生的婴儿或者出生时体重较轻的婴儿更容易是左撇子；母亲在怀孕时承受不同寻常的高强度压力，更容易生出左撇子的孩子。综合判断选项，造成左撇子可能的原因之一是C)“母亲在怀孕时遭受高强度的压力”。A)“左撇子的生活环境压力大”曲解原文中的“environmental factors…in the womb”(子宫环境)，故排除；虽说遗传是导致偏手性的部分原因，但不能由此而推断B)“左撇子受遗传的影响更大”，故排除；D)“母亲生产时体重可能减轻了”在文中找不到依据，故排除。
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