Why is Yawning Contagious?

Yawning is a reflex involving deep inhalation and stretching of eardrums, often linked to sleepiness, tiredness, or boredom. It is contagious among humans and some animals. In animals, yawning serves various functions, such as displaying teeth in baboons or courtship in penguins. Theories suggest yawning helps release carbon dioxide, keeps animals alert, or cools the brain. Studies indicate yawning might cool the brain by increasing oxygen intake. Excessive yawning could signal fatigue, suggesting rest is needed.

What theories exist regarding the evolutionary purpose of yawning?

What might excessive yawning indicate about a person's state?