By Dr. Brian McDonough

KYW Medical Reports Sponsored By Independence Blue Cross

By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) – Why do we yawn? And furthermore, why is yawning contagious? Have you asked yourself that question? I know that I have done it many times.

Evidence suggests that yawning is a way to communicate changing environmental or internal body conditions to others. If so, then its contagious nature is most likely a means of communication within groups of animals. We don’t need this now because we can talk, but at an earlier evolutionary stage, it might have been necessary.

As for why we yawn in the first place, there is a theory. It is in response to getting more oxygen, but this has been shot down by many.

We do know that a part of the brain called the periventricular nucleus is the yawning center of the brain. It contains a number of chemical messengers that can induce yawns, including dopamine, glycine, oxytocin and acth. I am getting technical so I will stop at this point – can’t bear to have you yawn.