Why Is Yawning Contagious??

It is a universally accepted fact that "yawning" is an act highly contagious. Even reading or discussing the topic makes one yawn, let alone sitting next to a person doing it.*YAWN*

The exact reason for yawning has not even been discovered by scientists yet.There was once a theory of oxygen and C02 balance associated with it but that one has been negated now. Some scientists do believe however that Yawning is related to boredom or inactivity in humans. The thought of it being caused by sleepiness  is a wrong concept since we all know that even when one wakes up in the morning after a 7, 8 or even 14 hour sleep, he is sure to yawn.

Scientists also claim that yawning is a social behavior observed by all species who possess a spinal cord (i.e vertebrates) and also that the reason to yawn is different for all.
*YAWN*
One might do it in boredom while another does it in times of hyper-activity.

Contagious Yawning is a powerful force.Although all vertebrates yawn, contagious yawning only exists only humans, chimpanzees and possibly dogs. One study suggests that yawning when others yawn, is a sign of empathy and a form of social bonding.Kids develop this rooted behaviour after at least age of four. Kids with autism are half as likely to catch yawns and the most severe cases might never do.

"Emotional contagion seems to be a primal instinct that binds us together," said Molly Helt, a graduate student in clinical psychology at the University of Connecticut, Storrs. "Yawning may be part of that."

References:[1]Hasb e hal, dunya news 

[2]Discovery.com