Question: Why do people yawn after another person yawns and are yawns contagious?

Answer: Yawning is a common but poorly understood behavior. It is characterized by the gaping of the mouth accompanied by a long inspiration followed by a shorter expiration. Despite many attempts to identify the function of yawning in humans and animals, scientists still debate over its significance.

Having been documented across many vertebrate species, however, it is agreed that yawning is an evolutionarily old behavior with important basic functions. Although it is most commonly thought of as a sign of boredom or fatigue, yawning also occurs under a variety of other conditions such as stress and anxiety or migraine headaches

http://www.pressconnects.com/article/20111209/NEWS02/111209006/Ask-Scientist?odyssey=mod%7Cnewswell%7Ctext%7CFRONTPAGE%7Cp

I've heard many times about the link between yawning and migraines, but I've never actually noticed it in myself. I yawn when I'm cold, which was always a bit embarrassing when I was cold in a meeting at work!

Oh I get it for sure about 2 days before I get a big one - it happens at the same time as the need to wee for England lol