You know the feeling. It’s getting close to bedtime, you get sleepy, and you start yawning automatically. You may even find yourself yawning in the middle of the day in a mid-day lull.

Bournemouth University neuropsychologist Simon Thompson is an expert on yawning. In 2011, he posited that high levels of the stress hormone cortisol may be a direct cause of yawning. “We believe that ...

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. Even more complex? Why we seem to yawn because ...