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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.
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Brain temperature rises slightly before sleep and during mental fatigue, triggering yawns to restore optimal function.
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Contagious yawning—copying others—is linked to empathy and social bonding, appearing reliably after age four.
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People with autism spectrum traits or high psychopathy scores yawn less frequently in response to others’ yawns.
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MRI scans show mirror neuron networks activate both when we yawn and when we watch someone else yawn.
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Even dogs yawn contagiously after seeing their owners yawn, suggesting deep evolutionary roots in social species.
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Athletes sometimes yawn before competition to increase alertness and oxygenate key brain regions.
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While often tied to boredom, yawning itself reflects a healthy, responsive nervous system—not laziness or lack of oxygen.