TPO18-1 The mystery of yawning打哈欠的奥秘
本篇文章反驳了一个关于打哈欠原因的传统理论，因此把握住观点的落脚点很重要，本篇有数道细节题都可从观点入手解决。因此，今天我们也是从句间逻辑关系和观点的角度对这篇文章进行解析。
1. According to conventional theory, yawning takes place when people are bored or sleepy and serves the function of increasing alertness by reversing, through deeper breathing, the drop in blood oxygen levels that arecaused by the shallow breathing that accompanies lack of sleep or boredom. Unfortunately, the few scientific investigations of yawning have failed to find any connection between how often someone yawns and how much sleep they have had or how tired they are. (开篇一道句子简化题，然后话锋一转，一个unfortunately即表明作者对conventional theory的态度，第二题事实信息题也迎刃而解了。)
2. When researchers measured the heart rate, muscle tension and skin conductance of people before, during and after yawning, they diddetect some changes in skin conductance following yawning, indicating a slight increase in physiological activity. However, similar changes occurred when the subjects were asked simply to open their mouths or to breathe deeply. Yawning did nothing special to their state of physiological activity.(修辞目的题考点：转折后下结论，把握句间逻辑关系有助把握观点和中心。)
3. If the theory was correct, breathing air with extra carbondioxide should have triggered yawning, while breathing pure oxygen should have suppressed yawning. In fact, neither condition made any difference to the frequency of yawning, which remained constant at about 24 yawns per hour.(体会in fact在句间起到的转折作用。)
4. According to this theory, yawning in adults is just adevelopmental fossil with no biological function. But, while accepting that note very thing in life can be explained by Darwinian evolution, there are soundreasons for being skeptical oftheories like this one, which avoid the issue of what yawning does for adults.(依然是转折后表明态度，考察观点型事实信息题出处。)
5. Yawning bore no relationship to sleep patterns, however. This accords with anecdotal evidence that people often yawn in situations where they are neither tired nor bored, but are preparing for impending mental and physical activity.(观点句，以此可解此段两道题。)
6. Their yawning seems to have nothing to do with sleepiness or boredom—quite the reverse—but it does precede a change in activity level.(篇章末尾总结句。)
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