雅思阅读模拟试题一例.pdf

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1、雅思阅读模拟试题一例雅思阅读模拟试题一例Right and left-handedness in humansWhy do humans, virtually alone among all animal species,display a distinct left or right handedness? Not even ourclosest relatives among the apes possess such decidedlateral asymmetry, as psychologists call it. Yet about 90per cent of every huma

2、n population that has ever livedappears to have been right-handed. Professor Bryan Turnerat Deakin University has studied the research literature onleft-handedness and found that handedness goes withsidedness. So nine out of ten people are right-handed andeight are right-footed. He noted that this d

3、istinctiveasymmetry in the human population is itself systematic.Humans think in categories: black and white, up and down,left and right. Its a system of signs that enables us tocategorise phenomena that are essentially ambiguous.Research has shown that there is geic or inherited elementto handednes

4、s. But while left-handedness tends to run infamilies, neither left nor right handers will automaticallyproduce off-spring with the same handedness; in fact about6 per cent of children with two right-handed parents willbe left-handed. However, among two left-handed parents,perhaps 40 per cent of the

5、children will also be left-handed. With one right and one left-handed parent, 15 to 20per cent of the offspring will be lefthanded. Even amongidentical twins who have exactly the same genes, one in sixpairs will differ in their handedness.What then makes people left-handed if it is not simply geic?O

6、ther factors must be at work and researchers have turnedto the brain for clues. In the 1860s the French surgeon andanthropologist, Dr Paul Broca, made the remarkable findingthat patients who had lost their powers of speech as aresult of a stroke (a blood clot in the brain) hadparalysis of the right half of their body. He noted thatsince the left hemisph