Chapter 19 Exercise 39, Page 422

Exercise 39

Page 422

Why We Yawn

Have you ever noticed that when a person near you yawns, you may start yawning too?

This is called contagious yawning. Contagious in this sense means that the behavior spreads: in the case of yawning, when one person yawns, it can cause others to do the same thing.

There are various theories about why people yawn. One popular idea is that yawning brings more oxygen into the brain so that people will wake up. Is that what you have thought?

However, in 2007, researchers at a university in New York came up with a new idea: yawning helps cool the brain. When people’s brains are warm, they yawn more frequently; yawning brings cooler air into the body and, therefore, cools the brain.

This is important because cooler brains work better than warmer ones.

This may also help explain why yawning is contagious. People are more awake when their brains are cooler; therefore, contagious yawning helps people be more alert.

As people evolved, this was important in times of danger. If they yawned, they could have been signaling to others to stay awake.

While it can be annoying to have a person yawn when you are talking, perhaps you can tell yourself that he or she actually wants to stay awake, not go to sleep.