疲劳理论的另一个缺陷是，打哈欠并不能像该理论所预测的那样，提高警觉性或生理活跃度。

Another flaw of the tiredness theory is that yawning does not raise alertness or physiological activity, as the theory would predict.

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不幸的是，少数针对打哈欠的科学调查未能发现人们打哈欠的频率与他们睡觉时长和疲劳程度之间有任何联系。

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.

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