Yawning: Why we do it and what it means
Last reviewed Sat 15 July 2017
By Jon Johnson
Whilst yawning is often considered a result of being tired or bored, this may not always be the case.
A yawn is an involuntary reflex where the mouth is opened wide, and the lungs take in a lot of air. The air is then exhaled slowly. During this time, the eardrums stretch, and the eyes may also close tight, causing them to water.
No thought or action has to be taken to produce a yawn, and the process is similar for everyone. Yawning commonly occurs either before or after sleep, which is why it is usually considered a sign of being tired. Yawning also occurs frequently in people who are doing boring or tedious things.
http://www.medicalnewstoday.com/articles/318414.php
