十万个为什么·科学阅读30篇（1）
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Why Do We Yawn When We’re Tired—or Even When Others Do?
为什么我们疲倦时打哈欠，甚至看到别人打也跟着打？
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Yawning cools the brain by drawing cool air deep into the sinus cavities, which then chill nearby blood vessels.打哈欠通过将冷空气吸入鼻窦腔，进而冷却附近的血管，从而为大脑降温。
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Brain temperature rises slightly before sleep and during mental fatigue, triggering yawns to restore optimal function.入睡之前或精神疲劳时，大脑温度会轻微升高，从而触发打哈欠以恢复最佳功能。
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Contagious yawning—copying others—is linked to empathy and social bonding, appearing reliably after age four.传染性打哈欠（模仿他人）与共情能力和社会联结相关，通常在四岁后稳定出现。
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People with autism spectrum traits or high psychopathy scores yawn less frequently in response to others’ yawns.自闭症谱系特质较明显或心理病态评分较高的人，对他人的哈欠反应更少。
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MRI scans show mirror neuron networks activate both when we yawn and when we watch someone else yawn.核磁共振成像显示，我们自己打哈欠或观看他人打哈欠时，镜像神经元网络均会被激活。
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Even dogs yawn contagiously after seeing their owners yawn, suggesting deep evolutionary roots in social species.就连狗在看到主人打哈欠后也会出现传染性哈欠，表明这一现象在社会性物种中具有深远的进化根源。
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Athletes sometimes yawn before competition to increase alertness and oxygenate key brain regions.运动员有时在比赛前打哈欠，以提升警觉性并增加关键脑区的供氧。
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While often tied to boredom, yawning itself reflects a healthy, responsive nervous system—not laziness or lack of oxygen.尽管常与无聊相关，打哈欠本身反映的是健康、灵敏的神经系统，而非懒惰或缺氧。