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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

admin2021-09-25  35
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 is the main idea of the passage?
选项 A、The causes for handedness in children.
B、Some fun facts about lefties.
C、The advantages and disadvantages of being left-handed.
D、Biological basis of handedness.
答案A
解析 主旨题。纵观全文，作者主要给出了两个研究的案例，探讨了关于用手偏好问题的原因，因此答案选[A]。[B]过于片面，文中提到的是科学实验，而非仅仅只是有趣的事实；[C][D]都不是基于本文的总结和论述。
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