A response to decreased oxygen and increased carbon dioxide: While this was a common belief for a while, there is no evidence that this is indeed true.
Yawning helps us bring more
oxygen into the blood and move more
carbon dioxide out of the blood.
Yawning, then, would be an involuntary reflex (something we can't really control) to help us control our
oxygen and
carbon dioxide levels.As
carbon dioxide builds up in the blood, a message to the brain results in signals back to the lungs saying, "Take a deep breath," and a
yawn is produced.
