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Biology 103
2003 Second Paper
On Serendip

Catch A Yawn

HoKyung Choi

A trick in every girl's handbook: If you want to know if someone is checking you out, yawn and check to see who, if anyone, yawns back. While we may be using the contagious phenomenon of yawning to our advantage, the age-old question still lingers on - why, in fact, is yawning contagious? Plausible explanations range from historic origins to muscular requirements. However, one answer that encompasses all other questions about the cause and traits of yawning has yet to be found.

First, let's tackle the question of why we yawn. An evolutional/psychological theory has claimed that yawning was once used as a non-verbal form of communication to synchronize group behavior among animals (9). For example, the leader of a pack of wolves would yawn to set a certain mood or signal a change of activity. Humans also being group-oriented animals may have assimilated to this form of agreement. In the same way that one pumped up team member can influence the level of aggression and team-spirit of an entire team, one yawning client can also affect the mood of sales-pitch meeting. Another good example of synchronization among humans is if a group is sitting around a campfire and the leader yawns, it most likely will act as a signal to the others that it may be time to call it a night.

Yawning is commonly perceived to be a sign of boredom or tiredness. Dr. Robert Provine, known as the yawn-expert from the University of Maryland, performed a study on 17-19 year old students to test this perception. In comparison to a group of students who watched music videos for 30 minutes, a group who watched an uninteresting color test bar pattern for 30 minutes yawned more (10). Dr. Provine also suggested that yawning is like stretching (5). Much like stretching, blood pressure and heart rate can be increased just by yawning. Perhaps animals yawn instinctively when bored or tired to get their blood pumping so that they may be physically stimulated to move or seek a new activity. But then why is it that we yawn after waking up? If we yawn after waking as a physical prompt to become active that's one thing. But yawning as a sign of tiredness can be ruled out if we yawn after waking from a restful sleep. Maybe a study could be done in which a comparison could be made between the hours of sleep and the occurrence of yawning when waking.

Above all, the most widely known reason for yawning is because our lungs need more oxygen. Medical schools teach that animals do not use their entire lung capacity when breathing normally. Because the alveoli, air sacs on the lower portion of the lungs, partially collapse when they do not receive fresh air, the brain is thought to signal the body to yawn or sigh to take in more oxygen (1). Along the same lines, when a person is bored his or her breathing slows and thus less oxygen is brought into the lungs.

However, I disagree with this lack of O2 theory for several reasons. First, Dr. Provine set up another experiment in 1987 to test this theory that yawning is caused by high CO2/low O2. Results showed that the test subjects' number or length of yawns were not affected by breathing 100% of O2 for 30 minutes (1). Therefore, this particular study acts as evidence the lack of O2 is not cause of yawning. To further support my disagreement of the O2 theory is the fact that an 11 week old fetus can yawn. Since fetuses do not receive oxygen to the lungs it has no reason to compensate a lack of oxygen in their alveoli. Additionally, just watching, hearing, or even reading about yawning can cause a person to yawn. Even if a person on TV is in a room with low levels of oxygen per say, regardless of the oxygen level in the room of the viewer, the viewer will still yawn.

This brings us to the next question: Why is yawning contagious? Some have agreed with Walter Smitson, professor of psychiatry at University of Cincinnati Medical Center, that as social creatures we are highly inclined to copy one another (2). If yawning is indeed related to mood, the suggestion of one person being tired, bored, or lacking oxygen can cue, alert, or suggest to others in the group to feel the same. This can also be linked to the previously suggested cause of yawning as a synchronizing behavioral act.

The "copycat" theory can be supported by the similar phenomenon humans find with tearing. When a child sees its mother crying it is natural for it to also cry. Even though it could be attributed to a maternal connection to one's mother, it could also be that as a helpless follower the child takes its mother's tears as a behavioral sign that something is wrong and mimics its leader. But does this then somehow imply that women or females are more sensitive to each other's feelings?

Although not a very strong supporting fact, it is often true that seeing, hearing, or even just reading about someone else's tears of pain or sadness can cause the recipient to also tear - granted this may be more applicable to women or that this "copycat" tearing could be a result of various emotional factors. Or is this an indication that women have stronger behavioral synchronization? After all, many more women than men choose to cry together - female support groups such as divorcee groups are more common than male support groups.

Then why is it a fact that men yawn more than women? (2) Dr. George Bubenik from the University of Guelph brings the debate back to the theory of supplying oxygen to the body. He proposes that, based on the O2 theory, men yawn more than women due to their larger muscle mass, which in turn require more oxygen. From a very general standpoint with the minimal data provided Dr. Bubenik's idea could be valid to a certain degree. If a legitimate connection between muscle mass and yawning can be made, perhaps it could support the O2 theory to be true.

Overall, there seems to be more research done on the causes and reasons for yawning than the contagious factor of yawning. So, I did some of my own research by asking others about their thoughts on the subject. The best suggestion I gathered was the possibility of a domino-effect theory. Some time long ago, one yawn could have been "caught" by several people and spread like a continual virus to others who passed it on to even more people and the cycle just never stopped. Therefore, someone is always "catching" someone else's yawn somewhere.

In the end, the answer to why animals yawn or what makes yawning contagious may not be as straightforward as we would all like. But discovering and dissecting an array of answers is what makes animals, oxygen, emotions, behaviors, our bodies, and science so interesting. Whether you yawn because you are signaling our boredom to others or because we are lacking oxygen in our alveoli, drop our jaw, yawn the average 6-second yawn, and just try checking who's yawning back.


1) MSNBC News, "Why we yawn."

2) Reily, Mary. E-briefing, "A Real Yawner: Causes, Concerns and Communications of the Yawn."

3) Hughes, Ron. Science Shorts, "What Makes You Yawn?"

4) Hughes, Ron. Science Shorts, "What Makes You Yawn?"

5) Neuroscience for Kids - Yawning.

6) Wong, A. Scientific American, "Why do we yawn when we are tired? And why does it seem to be contagious?"

7) Argiolas A, Melis. "The neuropharmacology of yawning."

8) Provine, R. PubMed, "Yawning: no effect of 3-5% CO2, 100% O2, and exercise."

9) Raphael, Rebecca. ABC News, "Is Yawning Contagious? Understanding Behaviors That Are Out of Our Control."

10) Dobson, Roger. Yawning Explained, "If you yawn, you're a human dynamo."

11) Provine, R.R. Yawning: effects of stimulus interest. Bulletin Psychonomic Sociology, 24:437-438, 1986.

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