Interestingly, while all vertebrates (including fish) yawn, only humans, chimps and possibly dogs find yawns contagious. And people don't find them contagious until they're about 4 years old. Recent studies show contagious yawning may be linked to one's capacity for empathy [source: Sohn].
In one study, autistic and non-autistic children were shown videos of people yawning and people simply moving their mouths. Both groups of kids yawned the same amount when viewing the video of people moving their mouths. But the non-autistic kids yawned much more frequently than those with autism when watching people really yawning. Since autism is a disorder that affects a person's social interaction skills, including the ability to empathize with others, the autistic kids' lack of yawning when watching others do so could indicate they're less empathetic. The study also found the more severe a child's autism, the less likely he or she was to yawn. On a positive note, someday doctors may be able to diagnose cognitive disabilities in young children more easily by seeing whether or not they can catch a yawn from others [sources: Kahn, Sohn].
So even though we still don't know for sure why we yawn, we do know lots of interesting things about yawning: you start yawning in utero; you yawn when you're aroused; more than half of you will yawn if you see someone else yawn; and reading about yawning makes you yawn [source: Sohn].
So, how many times did you yawn while reading this article? We hope not too many.
More Great Links
- Alexander, Brian. "If sex is a yawn, you may actually be turned on." MSNBC. July 30, 2009. (June 8, 2011) http://www.msnbc.msn.com/id/32205127/ns/health-sexual_health/t/if-sex-yawn-you-may-actually-be-turned/
- Encyclopedia Britannica. "Vagus Nerve." (June 15, 2011) http://www.britannica.com/EBchecked/topic/621522/vagus-nerve
- Fountain, Henry. "Tarzan, Cheetah and the Contagious Yawn." The New York Times. Aug. 24, 2004. (June 6, 2011) http://www.nytimes.com/2004/08/24/science/tarzan-cheetah-and-the-contagious-yawn.html
- Highlights Kids. "What causes a person to yawn? (June 6, 2011) http://www.highlightskids.com/Science/ScienceQuestions/h1sciQcausesYawn.asp
- Kahn, Michael. "Empathy can spark contagious yawning: study." Reuters. Aug. 14, 2007. (June 6, 2011) http://www.reuters.com/article/2007/08/14/us-yawning-study-idUSL1483150220070814
- Krulwich, Robert. "The Quest to Design the Perfect Yawn." National Public Radio. Sept. 24, 2007. (June 8, 2011). http://www.npr.org/templates/story/story.php?storyId=14654608
- Nagourney, Eric. "Insights: Big Yawn, Cooler Brain? Researchers Say Yes." The New York Times. July 3, 2007. (June 6, 2011) http://www.nytimes.com/2007/07/03/health/03insi.html
- Newburg, Andrew. "Yawn. It's one of the best things you can do for your brain." The Pennsylvania Gazette. November 2009. (June 8, 2011) http://www.upenn.edu/gazette/1109/expert.html
- The New York Times. "Yawning: Excessive." (June 6, 2011) http://health.nytimes.com/health/guides/symptoms/yawning-excessive/overview.html
- Patterson, Lindsay. "Robert Provine on why we yawn." Earth Sky. July 21, 2008. (June 8, 2011). http://earthsky.org/health/why-do-we-yawn
- Pediatric On Call. "Why Do We Yawn?" (June 6, 2011) http://www.pediatriconcall.com/kidscorner/whywhat/Why_yawn.aspx
- Randerson, James. "Yawning is catching in chimps." New Scientist. July 21, 2004. (June 6, 2011) http://www.newscientist.com/article.ns?id=dn6182
- Right Health. "Yawning: Excessive Guide." (June 6, 2011) http://www.righthealth.com/topic/What_Causes_Yawning?p=l&as=goog&ac=519&kgl=7763513
- Sohn, Emily. "Why Is Yawning Contagious?" Discovery News. Sept. 15, 2010. (June 6, 2011) http://news.discovery.com/human/yawning-social-behavior.html
- The Stress of Life. "One Good Yawn Is Worth Another But Psychologists Are Still Baffled." Aug. 15, 2003. (June 14, 2011) http://thestressoflife.com/one_good_yawn_is_worth_another_b.htm
- University of Washington. "Why Do We Yawn and Why Are Yawns Contagious?" July 31, 2007. (June 6, 2011) http://staff.washington.edu/~chudler/yawning.html