While scientists have many ideas, they are not certain why humans yawn(打哈欠). Still, there is one thing experts know—yawns seem to be contagious(传染)!

Have you ever caught a yawn from someone else? Most people have. In fact, a person is six times more likely to yawn after seeing someone else do so. Experts have done many studies into why yawns seem to pass from person to person. As a result, they have a few theories(理论) for the reason behind it.

One possible explanation has something to do with social mirroring, which is caused by mirror neurons(镜像神经元) in the brain. These mirror neurons help the brain notice useful behavior of others and then copy it. When one person sees another yawn, his mirror neurons observe the action and consider it to be beneficial. That may cause him to yawn, too.

Another popular theory is that yawns are contagious because of social relationships. Being social creatures, humans form friendships, families and live together in groups. That’s why many people mirror others, such as smiling when another person smiles. Yawning may be just another example of this. In fact, research has shown that one is most likely to catch yawns from another person if the two share a social relationship.

The answer could even be that yawns aren’t truly contagious at all. Instead, people yawn together simply because they’re in the same environment. Experts say many things may cause yawning, including temperature and time of day. Whatever the explanation is, experts do know that contagious yawns aren’t limited to humans. One study found that lions in South Africa also caught each other’s yawns.

【小题1】What kind of behavior may be copied by mirror neurons?

A．Important and attractive.	B．Useful and beneficial.
C．Hard to understand.	D．Easy to copy.

【小题2】Whose yawns are people most likely to catch according to Paragraph 4?

A．Those who yawn a lot.	B．Those who like smiling.
C．Those closely connected with them.	D．Those sharing the same interest with them.

【小题3】What might the author continue talking about in the following paragraph?

A．Tips on how to avoid yawning in public.

B．A real explanation for contagious yawning.

C．Other examples of animals yawning together.

D．Things that may cause yawning among humans.

【小题4】Which of the following serves as the best title?

A．Why yawns are contagious	B．What causes people to yawn
C．Who yawns more than others	D．Why humans yawn now and then