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  3. Globally, 10. 6 percent of people are left-handers, while the remaining 89. 4 percent are righthanders. While it is widely assum

Globally, 10. 6 percent of people are left-handers, while the remaining 89. 4 percent are righthanders. While it is widely assum

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问题     Globally, 10. 6 percent of people are left-handers, while the remaining 89. 4 percent are righthanders. While it is widely assumed that handedness is influenced by both genetic and environmental factors, it is still not well understood why some people become left-handed and others become right-handed.
    One longstanding hypothesis proposed in 1973 by Paul Satz, an American psychologist, and one of the founders of the discipline neuropsychology, is that the circumstances surrounding birth could affect handedness. It has been suggested that being born extremely early or under very stressful conditions could raise the chances of being left-handed—the so-called " early insult" hypothesis for left-handedness. This theory assumes that early brain damage caused by birth complications could lead to a switch in handedness. As there are more people who are initially right-handed, there would be more "pathological" left-handedness than "pathological" right-handedness caused by this switch. Thus, the theory would assume that having problems with birth would result in a higher amount of brain damage and a higher chance of being left-handed.
    But is this really the case? While previous studies have often investigated the link between birth complications and handedness, I think they often neglected to also obtain brain scans in order to assess whether or not there was any brain damage. A new study by Van Heerwaarde from the Netherlands in 2020 now investigated whether being born extremely preterm affects handedness.
    In the study, the scientists evaluated handedness at school age (4-8 years) in 179 children that were born extremely preterm. The mean gestational age of the children was 26. 5 weeks, compared to 38-42 weeks in full-term born babies. The handedness assessment showed that in the children that were born extremely preterm 19. 6 percent were left-handers, 3. 4 percent were mixed-handers and the remaining 77. 1 percent were right-handers. This indicates that there were more lefthanders and mixed-handers among children that were born extremely preterm than among children that were born full-term (in the general population, 89.4 percent of people are right-handers).
    But were left-handedness and mixed-handedness linked to brain damage? Importantly, the authors obtained brain scans to assess brain damage. The scientists used magnetic resonance imaging to find out. Their brain scans showed that overall about 47 percent of preterm-born children showed one or more lesions in the brain, which is substantially more than in full-term born babies. However, there was absolutely no statistical link between left-handedness and mixed-handedness and brain damage. The scientists then used another type of brain scan to assess damage in the white matter of the brain. Again, absolutely no relation to handedness was found.
    Taken together, the study by Van Heerwaarde (2020) clearly shows that left-handedness and mixed-handedness are more common in children that were born extremely preterm than in children that were born full-term. Moreover, they also show that it is highly unlikely that brain damage causes left-handedness as no relation between handedness and brain damage was found. This suggests that other factors linked to being born extremely preterm are likely affecting handedness.
What can we learn from Paragraph 1?
选项 A、Genetic and environmental factors are not relevant to handedness.
B、Studies still fail to explain the causes of handedness.
C、Handedness is decided at birth and can not be altered.
D、There is indeed a gender difference in handedness.
答案B
解析 细节题。在第一段中，作者提到了对于“为什么有些人是左利手，有些人是右利手”这一点仍然没有定论，因此答案选[B]。[A]与文义有出入，文中说到用手习惯受到遗传和环境因素的影响是很多人的普遍看法，但是这一句后面马上跟了转折的一句话，也就是对于偏好用左手还是右手这一点，没有定论；[C][D]属于无中生有的选项。
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