The average adult yawns about 20 times a day. But why? Surely we cannot all be that tired. The truth is the science behind yawning is much more complex than just a few hours too little sleep.

So why do we do it then? Well, new research suggests it might be because yawning cools the brain down and prevents it from overheating, much like the fan in your laptop. So, why do we yawn when tired?

There thus can be no unitary explanation for why we yawn but it would seem to serve ... “with immediate improvement, reading 30 books in four months and building a model of the Hoover Dam ...