Why Do We Yawn?

Why do we yawn? If you think the answer is BOR-ing, then maybe your brain's just overheated. Let Hank explain the new thinking behind why we ... hold on ... *yawn*. Excuse me. Help support us by subscribing to our page on Subbable: https://subbable.com/scishow ---------- Like SciShow? Want to help support us, and also get things to put on your walls, cover your torso and hold your liquids? Check out our awesome products over at DFTBA Records: http://dftba.com/artist/52/SciShow ---------- Looking for SciShow elsewhere on the internet? Facebook:   / scishow   Twitter:   / scishow   Tumblr:   / scishow   Thanks Tank Tumblr:   / thankstank   Sources: http://www.upenn.edu/gazette/1109/exp... http://news.nationalgeographic.com/ne... http://www.nytimes.com/2007/07/03/hea... http://serendip.brynmawr.edu/exchange... http://www.loc.gov/rr/scitech/mysteri... http://www.smithsonianmag.com/science... https://www.princeton.edu/main/news/a... http://www.psychologytoday.com/blog/b... http://www.epjournal.net/wp-content/u...