Why do we yawn?
1Read
Everyone yawns — babies before they are born, dogs, cats, even fish. Yet scientists are still not completely sure why.
The old idea was that yawning brings in extra oxygen when we are tired. Experiments do not support this: people yawn just as much in rooms full of oxygen.
The best current idea is that yawning cools the brain. A deep yawn stretches the jaw, increases blood flow to the head and pulls in cool air. The brain works best at a steady temperature, and tired brains run warm. That is why we yawn more when sleepy and less in cold weather.
And yes, yawning is catching. Seeing or even reading about a yawn can trigger one — it may be a sign of empathy. Have you yawned yet?
2Words to learn
3Check your understanding
4Explain it
Speaking challenge
Explain the brain-cooling idea in your own words. Did you yawn while reading?
Say it out loud. Nobody is listening — that’s the point. Mistakes are allowed.