Why is yawning contagious?

That is a very good question - and thanks for clarifying, Beth. This gives me faith that your daughter is not simply a wisenheimer looking to make things difficult for the crack staff, drivers, floor managers, sous chef and paper-runners of the Just Ask Jerry Scientific Research Lab and Memorial Library. Since we put them through a wild goose chase to answer the same question regarding hiccups, which left them feeling depressed and empty after coming up with a less-than-fulfilling answer, this is our chance to allow them to get back into the swing of things by answering Emelia's true question.

(And what exactly is a wild goose chase? Perhaps another fine question to put the staff through their paces answering. Maybe not the entire staff - perhaps just the runners.)

If I were to hazard a guess as to why the yawn makes us yawn, I would like to think that it has something to do with self-preservation. A yawn is likely caused (as I have no doubt scientific research will verify) by our body struggling to feed itself the vital oxygen needed to live. When our body feels as if it is running a little short on the valuable chemical element "O", it steps on the yawn-pedal, like the carburetor of a classic V-8 automobile. When we see someone else yawn, our own carburetor revs, realizing that someone else is sucking more than their fair share of air, thus depriving our own body/engine of its own much-needed oxygen. So we rev our own motor to make sure we don't get light headed, pass out and bang our head on an end table.

This from Wikipedia: "One study states that yawning occurs when one's blood contains increased amounts of carbon dioxide and therefore becomes in need of the influx of oxygen (or expulsion of carbon dioxide) that a yawn can provide. Yawning may in fact reduce oxygen intake compared to normal respiration. But giving people additional oxygen didn't decrease yawning, and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning.^"

Well, that shoots down my "O" theory. It has been suggested that yawning helps keep the brain cool, which I am all for. Then there is science...

Also from Wikipedia: "Another hypothesis is that yawns are caused by the same chemicals (neurotransmitters) in the brain that affect emotions, mood, appetite, and other phenomena. These chemicals include serotonin, dopamine, glutamic acid, and nitric oxide. As more (or less) of these compounds are activated in the brain, the frequency of yawning increases. Conversely, a greater presence in the brain of opioid neurotransmitters such as endorphins reduces the frequency of yawning."

See? That was easy.

Now, as to the contagious yawn...

From the World-Wide Web: "Explanations include the idea that yawning may have evolved in early man as a way to signal or set up sleep schedules. A contagious yawn meant that perhaps more than one person was tired and people should sleep accordingly. Since tiredness might indicate a less energetic response to danger, yawning would mean people should find shelter and get out of danger. Those who yawned and paid attention to it may have been selected into the species because they got proper sleep and were more alert to danger."

Apparently, the yawn acts as a sort of reverse-alarm clock. Another theory suggests that the contagious yawn is a sign of empathy, which I also like, since it also helps keep the brain cool. One cannot be too careful when it comes to the brain overheating. So, by all means be empathetic - yawn with others. Your brain will thank you.

Wiki continues: "The proximate cause for contagious yawning may lie with mirror neurons in the frontal cortex of certain vertebrates... Mirror neurons have been proposed as a driving force for imitation which lies at the root of much human learning such as language acquisition. Yawning may be an offshoot of the same imitative impulse."

So, contagious yawning is not only empathetic and useful for maintaining a reasonable brain-temperature, it is also a learning instrument. One thing I am certain of moving forward is that when my boss yawns at work, I will take the opportunity to yawn in response, declare that it is time for some "learning time" and put my cool head down on my desk for a little nap. It's just good science.

Good day, Sir.