You've probably seen someone yawn and felt compelled to take a deep inhale and exhale yourself. Yes, yawning is contagious, but why do we actually do it in the first place? Trace takes a look at the competing theories out there. Read More: http://www.loc.gov/rr/scitech/mysteries/yawn.html Development of Fetal Yawn Compared with Non-Yawn Mouth Openings from 24-36 Weeks Gestation http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050569?imageURI=info:doi/10.1371/journal.pone.0050569.g001 "Although some research suggests that fetuses yawn, others disagree arguing that is it simple mouth opening." Why Do You Yawn When You're Not Sleepy? http://www.psychologytoday.com/blog/brain-sense/201111/why-do-you-yawn-when-youre-not-sleepy "Maybe because your brain is overheated." What makes us yawn? http://science.howstuffworks.com/life/inside-the-mind/human-brain/question572.htm "Next time you're in a meeting, try this little experiment: Take a big yawn, cover your mouth out of courtesy and watch to see how many people follow suit." Facts About Yawning: Why We Do It, Why It's Contagious And More http://www.huffingtonpost.com/2013/06/10/facts-yawning-why-we-yawn-contagious_n_3398301.html "We all do it, and we all know it has at least something to do with how tired we feel." Yawning as a brain cooling mechanism: Nasal breathing and forehead cooling diminish the incidence of contagious yawning http://www.epjournal.net/articles/yawning-as-a-brain-cooling-mechanism-nasal-breathing-and-forehead-cooling-diminish-the-incidence-of-contagious-yawning/ "We conducted two experiments that implicate yawning as a thermoregulatory mechanism." Human paranasal sinuses and selective brain cooling: A ventilation system activated by yawning? http://www.medical-hypotheses.com/article/S0306-9877(11)00414-2/abstract "The function of the paranasal sinuses has been a controversial subject since the time of Galen, with many different theories advanced about their biological significance." Really? Yawning Is Contagious Between Dogs and Their Owners http://well.blogs.nytimes.com/2013/08/19/really-yawning-is-contagious-between-dogs-and-their-owners/ "Yawning when you see someone else yawn is thought to signal empathy." Watch More: How Our Internal Clock Works http://www.youtube.com/watch?v=jFfAbMbrZrA Why We Blush http://www.youtube.com/watch?v=IjG8p0icOTg Awesome Ferrofluid Sculptures http://www.youtube.com/watch?v=XJSZsgTaRAQ ____________________ DNews is dedicated to satisfying your curiosity and to bringing you mind-bending stories & perspectives you won't find anywhere else! New videos twice daily. Watch More DNews on TestTube http://testtube.com/dnews Subscribe now! http://www.youtube.com/subscription_center?add_user=dnewschannel DNews on Twitter http://twitter.com/dnews Anthony Carboni on Twitter http://twitter.com/acarboni Laci Green on Twitter http://twitter.com/gogreen18 Trace Dominguez on Twitter http://twitter.com/trace501 DNews on Facebook http://facebook.com/dnews DNews on Google+ http://gplus.to/dnews Discovery News http://discoverynews.com