十万个为什么·科学阅读30篇（2）
9 / 30
正在确认阅读权限…
Why Do We Yawn When We’re Tired — And Why Is It Contagious?
人疲倦时为什么会打哈欠？而且它为什么会传染？
-
Yawning increases oxygen intake and cools the brain by drawing cool air over sinus membranes and blood vessels.
-
It often occurs before sleep or upon waking, helping regulate alertness and transition between mental states.
-
Contagious yawning is linked to empathy and social bonding, appearing strongly in humans and some primates.
-
Brain scans show that the same neural networks activate whether you yawn or just watch someone else yawn.
-
Children under five rarely catch yawns, suggesting the trait develops alongside theory-of-mind skills.
-
People with autism spectrum conditions yawn less contagiously, supporting the empathy connection.
-
Even reading or thinking about yawning can trigger it — a sign of strong mental simulation ability.
-
Yawning stretches jaw muscles and increases heart rate slightly, preparing the body for activity.
-
It’s not caused by low oxygen or high CO₂, as early theories claimed — controlled experiments disproved that.
-
This ancient, automatic behavior bridges physiology, psychology, and group survival in subtle ways.