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  3. In an experiment published last month, researchers from the University of Illinois recruited schoolchildren, ages 9 and 10 and a

In an experiment published last month, researchers from the University of Illinois recruited schoolchildren, ages 9 and 10 and a

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问题     In an experiment published last month, researchers from the University of Illinois recruited schoolchildren, ages 9 and 10 and asked them to run on a treadmill, hoping to learn more about how fitness affects the immature human brain.
    The researchers sorted the children, based on their treadmill runs, into highest-, lowest- and median-fit categories. Only the most- and least-fit groups continued in the study (to provide the greatest contrast). Both groups completed a series of cognitive (认知的) challenges. Finally, the children’s brains were scanned, using MRI technology to measure the volume of specific areas.
Previous studies found that fitter kids generally scored better on such tests. And in this case, too, those children performed better on the tests. But the MRIs provided a clearer picture of how it might work. They showed that fit children had significantly larger basal ganglia, a key part of the brain that aids in maintaining attention and "executive control". Since both groups of children had similar socioeconomic backgrounds, body mass index and other variables, the researchers concluded that being fit had enlarged that portion of their brains.
    The findings arrive at an important time. For budgetary and administrative reasons, school boards are reducing physical education, while on their own, children grow increasingly sluggish (懒散的). Roughly a quarter of children participate in zero physical activity outside of school.
At the same time, evidence accumulates about the positive impact of even small amounts of aerobic (有氧的) activity. Past studies found that "just 20 minutes of walking" before a test raised children’s scores, even if the children were otherwise unfit or overweight.
    But it’s the neurological (神经的) impact of sustained aerobic fitness in young people that is especially compelling. A years-long Swedish study published last year found that, among more than a million 18-year-old boys who joined the army, better fitness was correlated with higher IQs, even among identical twins. The fittest of them were also more likely to go on to profitable careers than the least fit, rendering them less likely to live in their parents’ basements.
    No correlation was found between muscular strength and IQ scores. There’s no evidence that exercise leads to a higher IQ, but the researchers suspect that aerobic exercise, not strength training, produces specific growth factors and proteins that stimulate the brain.
The University of Illinois experiment was different from previous studies in that .
选项 A、its researchers categorized the children only by fitness levels
B、it highlighted the importance of students’ running on a treadmill
C、it showed how being fit affects children’s performance on the tests
D、it asked the subjects to complete tests that were beyond their levels
答案C
解析 根据题干中的previous studies将本题出处定位到第3段前3句。这几句提到，以前的研究已经发现，身体更健康的小孩在这一类测试中得分较高。同样地，在该研究中，身体更健康的儿童也在测试中成绩更好。不过磁共振成像技术扫描更清晰地向人们呈现出这究竟是怎么发生的。由此可知，伊利诺斯州大学的实验与以前实验的不同在于它展示了身体健康是如何影响孩子在测试中的表现的，故答案为[C]。第2段首句提到研究人员是根据这些儿童在跑步机上的跑步情况将他们分成健康水平不同的三个小组的，并非根据他们的健康水平将他们分组，[A]与原文不符，故排除。文中提到让小学生 踩跑步机，但并没有强调踩跑步机的重要性，故排除[B]。文中提到让他们参加认知测试，但并未说这些测试超出他们的能力，故排除[D]。
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