Feature

Yawn

Latest research awakens debate over why people can’t keep their mouths closed

By Laura Sanders

- More than 2 years ago

Scratching relieves an itch, sneezing clears out the nose and drinking relieves thirst. And yawning … does something.

Joos Mind/Getty Images

COOLING YAWN Before a yawn, rats’ brain temperatures rose. Post-yawn, temperatures dropped. Yawning and stretching (and stretching alone) also showed cooling effects. E. Feliciano; Source: M.L. Shoup-Knox et al/Frontiers in Evolutionary Neuroscience 2010

Researchers have been trying to finish that sentence for centuries.