Yawn

body reflex · all animals · sleepy · science

A natural reflex. A yawn is something your body does automatically without you thinking about it. It happens in almost all vertebrate animals, including mammals, birds, reptiles, amphibians, and fish.

Three-part motion. A yawn starts with a long breath in as your mouth gradually opens wider and wider. Then your muscles stretch and tighten for a brief moment at the climax. Finally, you quickly breathe out and relax, and the whole thing is over in just a few seconds.

Fish yawn too. Even though fish and birds yawn differently than you do, they still yawn. For them, it means opening their mouth wide and keeping it open for at least three seconds, then snapping it shut quickly.

Studying yawns. Scientists who study yawning have a special name for what they do: chasmology. It comes from an old Greek word that means opening or gaping.