Why do we yawn?

Yawning photo by ytang3 @ flickr

Yawning photo by ytang3 @ flickr

What is the purpose of a yawn? We all do it on a near daily basis, most often when we least expect it. Yawning doesn’t take conscious effort, most of the time. Some people even think it’s contagious!

When we yawn no matter when or where we take in large gulps of air. So whats the purpose of this involuntary respiratory reflex? Well…the answer is we don’t know totally.

A few of the popular explanations are:

  • Yawning is our bodies way of regulating CO2 (carbon dioxide) levels.  When carbon dioxide blood gas levels reach a certain level our body will yawn in an attempt to increase the level of oxygen. A yawn is a large inhalation of air, and a slow exhalation. The longer the exhalation the better our body can strip the oxygen from the air, and exhale out carbon dioxide.
  • We yawn when we are tired, or bored. Yawning may be a way for your body to outwardly signal to you and others that you are ready to go to sleep. If you had been talking with Joe and it was late and Joe yawned, you would most likely finish up your conversation and let Joe go home and sleep right? Most of us would. The same thing with boredom. If you are giving a lecture on a subject and your students are yawning, that’s a good sign that what you are presenting to the class in not very interesting.

Is yawning really contagious?
Well, maybe…and maybe not. It is likely that when someone else yawns you yourself realise how tired you are and your body yawns as well. It is also possible that when someone yawns because their bodies level of co2 is low, and yours may be as well.

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