TPO 18-2 The Mystery of Yawning（生命科学--呵欠）

字数：730

建议做题时间20分钟

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 are caused 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. About the closest any research has come to supporting the tiredness theory is to confirm that adults yawn more often on weekdays than at weekends, and that school children yawn more frequently in their first year at primary school than they do in kindergarten.

Another flaw of the tiredness theory is that yawning does not raise alertness or physiological activity, as the theory would predict. When researchers measured the heart rate, muscle tension and skin conductance of people before, during and after yawning, they did detect 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. Experiments have also cast serious doubt on the belief that yawning is triggered by a drop in blood oxygen or a rise in blood carbon dioxide. Volunteers were told to think about yawning while they breathed either normal air, pure oxygen, or an air mixture with an above-normal level of carbon dioxide. If the theory was correct, breathing air with extra carbon dioxide 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. Another experiment demonstrated that physical exercise, which was sufficiently vigorous to double the rate of breathing, had no effect on the frequency of yawning. Again the implication is that yawning has little or nothing to do with oxygen.

A completely different theory holds that yawning assists in the physical development of the lungs early in life, but has no remaining biological function in adults. It has been suggested that yawning and hiccupping might serve to clear out the fetuses airways. The lungs of a fetus secrete a liquid that mixes with its mother's amniotic fluid. Babies with congenital blockages that prevent this fluid from escaping from their lungs are sometimes born with deformed lungs. It might be that yawning helps to clear out the lungs by periodically lowering the pressure in them. According to this theory, yawning in adults is just a developmental fossil with no biological function. But, while accepting that not everything in life can be explained by Darwinian evolution, there are sound reasons for being skeptical of theories like this one, which avoid the issue of what yawning does for adults. Yawning is distracting, consumes energy and takes time. It is almost certainly doing something significant in adults as well as in fetuses. What could it be?

The empirical evidence, such as it is, suggests an altogether different function for yawning—namely, that yawning prepares us for a change in activity level. Support for this theory came from a study of yawning behavior in everyday life. Volunteers wore wrist-mounted devices that automatically recorded their physical activity for up to two weeks: the   volunteers also recorded their yawns by pressing a button on the device each time they yawned. The data showed that yawning tended to occur about 15 minutes before a period of increased behavioral activity. 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. Such yawning is often referred to as "incongruous" because it seems out of place, at least on the tiredness view: soldiers yawning before combat, musicians yawning before performing, and athletes yawning before competing. Their yawning seems to have nothing to do with sleepiness or boredom—quite the reverse—but it does precede a change in activity level.

题目

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答案解析

1. 句子简化题

解析：原句结构为传统理论认为，yawning在什么情况下发生、有什么功能。A在功能部分只说到一半，没有说到reversing。B对。C原文没有该比较。D原文没说avoided的内容

2. 事实信息题

解析：根据tiredness theory定位到第1句，即关于呵欠的传统理论，认为打呵欠与无聊或困乏有关，而后文没有说到证明这个理论的证据，选A

3. 词汇题

解析：flaw缺点、漏洞，选A

4. 修辞目的题

解析：根据physiological changes, mouth定位到2-3句，这是两个例子，前者说明呵欠会引起心率等变化，后者说仅仅张嘴或深呼吸也会发生这样的变化，而段首句说传统理论的另一个缺点是呵欠不会导致警觉或生理活动，所以选C

5. 词汇题

解析：trigger引起、导致，选D

6. 事实信息否定题

解析：A对应第1句，对。B根据thinking about yawning定位到倒数第5句，原文只说到让志愿者在呼吸是想到呵欠，后句说如果理论是对的，呼吸更多二氧化有会导致呵欠，没有说到想到呵欠会增加呵欠，B错，选B。C对应倒数3-4句，对。D对应最后一句，对。

7. 词汇题

解析：period时期，periodically周期性地，选C。

8. 事实信息题

解析：根据developmental theory，role定位到1-2句，第2句说yawning清扫胎儿的气道，所以选D

9. 事实信息题

解析：A根据Darwinian定位到倒数第3句，说的是并非所有事情都可以用达尔文进化论解释，没有说到A中这个理论运用了达尔文进化论。B根据lung deformity定位到第4句，没有说到B中的解释。C根据adulthood定位到第4-5句，C对。D的evolutionary stage原文没说。选C

10. 词汇题

解析：empirical以实验为依据的，选D。原句后文说这个理论受到一项研究的支持，即这个证据是有实验基础的

11. 事实信息题

解析：问的是结论，段首句说打呵欠为我们的活动水平变化做准备，选A与即将升高的身体活动有关。BCD没说

12. 修辞目的题

解析：由such可知本句（例子）是对上句的补充说明，上句说打呵欠不是因为累或者无聊，而是为接下来的精神和身体活动做准备，选C

13. 句子插入题

解析：插入句说情况不是这样的，说明插入句前后说了两种相反的情况。B前后联系紧密，C前是一种假设的情况，C后出现in fact实际情况，说明前后是相反的，选C。

14. 段落小结题

解析：A中的earlier scientific studies原文没说，不选

B对应第3段第1句，正确

C没说，不选

D对应第2段第1句和最后一句，正确

E没说，不选

F对应最后一段第1句，正确

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