Yahoo Life Videos
Merely thinking about or seeing someone yawn can make you yawn (you’re probably yawning right now). Most people yawn because they’re tired, but it can also happen unexpectedly and without any triggers. While yawning is typically harmless and only lasts about five to 10 seconds, when it occurs excessively it can actually be a symptom of a serious condition. So why exactly do we yawn? And why is it nearly impossible to stifle a yawn when someone does it in front of you? Watch the video above — and read more here — to find out.