Why do we yawn?
Short answer
People often yawn when they feel sleepy or tired. Scientists still do not know exactly what yawning does for the body.
What role does yawning play?
A yawn involves opening the mouth wide and taking a deep breath. Researchers have suggested several possible roles, but they do not yet agree on one main purpose.
Why can seeing a yawn make you yawn?
Seeing another person yawn can sometimes make you yawn too. This is called contagious yawning, but it is not an infection like a cold. Researchers are still studying why it happens.