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Why Do We Yawn When We’re Tired—or Even When Others Do?
为什么疲倦时打哈欠，甚至看到别人打哈欠也会跟着打？
精读先不看文字，完整听一遍。
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Yawning cools the brain by increasing blood flow and drawing in cooler outside air through the mouth.打哈欠通过增加血流、从口腔吸入较凉的外界空气来为大脑降温。
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Brain temperature rises slightly before sleep and during mental fatigue, triggering this thermoregulatory reflex.入睡之前及精神疲劳时，大脑温度会轻微升高，从而触发这一体温调节反射。
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Contagious yawning likely evolved as a social cue to synchronize group alertness and rest cycles.传染性打哈欠很可能演化为一种社交信号，用以同步群体的警觉与休息节律。
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Studies show people with higher empathy scores yawn more readily when observing others yawn.研究表明，共情能力得分较高的人，在看到他人打哈欠时更容易随之打哈欠。
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Children under four rarely catch yawns, suggesting the trait develops alongside theory-of-mind abilities.四岁以下儿童极少出现传染性打哈欠，表明该能力随心理理论能力的发展而形成。
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Even dogs yawn contagiously after watching familiar humans—especially their owners—yawn.就连狗在观看熟识的人——尤其是主人——打哈欠后，也会出现传染性打哈欠。
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Yawning isn’t caused by low oxygen or high carbon dioxide, as older theories claimed.打哈欠并非如旧理论所称，由缺氧或二氧化碳浓度过高引起。
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Stretching during a yawn also stimulates facial nerves linked to wakefulness and attention.打哈欠时的伸展动作还能刺激与清醒和注意力相关的面部神经。
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In classrooms or meetings, shared yawning may subtly coordinate group focus and transition timing.在教室或会议中，集体打哈欠可能悄然协调群体的专注状态与转换时机。
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While mostly harmless, excessive yawning can sometimes signal neurological conditions needing evaluation.尽管大多无害，但频繁打哈欠有时可能是需就医评估的神经系统疾病的信号。
精读 · 大约 10 分钟
听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。
③ 学 · 重点表达
- Even dogs yawn contagiously after watching familiar humans—especially their owners—yawn. 就连狗在观看熟识的人——尤其是主人——打哈欠后，也会出现传染性打哈欠。
- While mostly harmless, excessive yawning can sometimes signal neurological conditions needing evaluation. 尽管大多无害，但频繁打哈欠有时可能是需就医评估的神经系统疾病的信号。
- Children under four rarely catch yawns, suggesting the trait develops alongside theory-of-mind abilities. 四岁以下儿童极少出现传染性打哈欠，表明该能力随心理理论能力的发展而形成。
④ 懂 · 选一选
⑤ 今天会说这一句
Even dogs yawn contagiously after watching familiar humans—especially their owners—yawn.
⑥ 跟读并录音
Even dogs yawn contagiously after watching familiar humans—especially their owners—yawn.
第一版：录下来、回听、再听标准音。系统打分以后再加。
⑦ 说 · 自己来一句
用今天的表达，自己说一句。
例子：Even dogs yawn contagiously after watching familiar humans—especially their owners—yawn.
已记下。连续天数以后会显示在课表里。
陈老师指导
课程开发中，敬请期待。成人和孩子都可以先自学听读、精读。
这边的讲解音轨还在做。想先跟着老师走完固定 30 课，可以去陈老师带读社（和自学通行不是同一份会员）。
课程开发中，敬请期待。