There are several theories about why we yawn. The most popular theory in recent years is that yawning is a way of cooling down the brain, which is not capable (1) ... working well when it's too hot. This may also explain why athletes often yawn just before competing. Although scientists have difficulty (2) ... agreeing about the reasons (3) ... yawning, one thing they all agree about is that yawning is catching: if you see someone yawn, you're likely to yawn, too. In fact, there is no need to see a person yawn  — just hearing someone yawn (4) ... the phone, or reading about yawning can produce a need to do the same. The chances are you’ll yawn (5) ... least once while reading this article.