Dear Bailey,

No one really knows for sure why we yawn or if it serves any useful function, and very little research has been done on the subject. One possible reason we yawn is to get more oxygen in our lungs and rid ourselves of carbon dioxide at those times when we are still and inactive, like when we are bored or drowsy. However, that doesn’t totally explain yawning because unborn babies do it and they don’t even take oxygen in through their lungs. You may also see Olympic athletes yawn before their event and they are not likely bored or drowsy.

Also, scientists have created situations where oxygen levels are low and carbon dioxide levels are high in the lungs but those conditions did not make people yawn any more than regular conditions. So we obviously yawn for other reasons that are not quite clear. A related possibility is that some of the tiny air sacs in the lungs, called alveoli, don’t have enough air in them so they partially collapse, the lungs stiffen, and the yawning reflex is a signal from the brain to bring more air into the lungs to open these small sacs or alveoli again.

Did you know that there are many parts of the body that are in action when you yawn? First, your mouth opens and jaw drops, allowing as much air to be taken in as possible. When you inhale, the air taken in is filling your lungs. Your abdominal muscles flex and your diaphragm is pushed down. The air you breathe in expands the lungs to capacity and then some of the air is blown back out. The average yawn takes about six seconds.

Yawning is clearly contagious, meaning other people will yawn just because they see someone else yawn. In fact, more than half of the people who see someone else yawn will yawn themselves. Many will yawn as they read this. Have you? Some scientists believe that yawning is a vestigial (or leftover) behavior that we really no longer need.

Thanks for your question,
Aubie and Dr. Wilson