You can feel it coming on — that sudden urge to nearly unhinge your jaw and suck in as much air as your lungs can handle. But why do we do it?
Yawning is a ubiquitous activity in humans, and many other species as well. But few hypotheses as to why we do it have been rigorously tested, leaving researchers with a whole lot of ideas and not much evidence to back them up. To this day, there is no general consensus on why we yawn — though some theories hold more weight than others.
What Does Yawning Do?
One of the oldest theories about yawning — dating back to Hippocrates’ time — is that it can increase blood circulation to the brain. But in recent decades, research has shown that there isn’t evidence to back up this idea.
