Why do we yawn? Know the truth behind this reflex!

Zee Media Bureau

New Delhi: One of the science's most baffling questions - why do we yawn? This behavioural phenomenon has puzzled scientists for more than two millennia.

Everybody yawns - from unborn babies to the great grandparents. Not just humans, even animals do it. But, no one knows exactly what causes people and animals to yawn. There are many theories and ideas behind this mysterious epidemic of yawning.

• Some people say that we yawn when we are bored or tired and when our blood contains increased amounts of carbon dioxide and therefore requires influx of oxygen. However, neither yawning gives more oxygen nor reduces carbon dioxide in the blood. Sometimes, a yawn comes on for no reason at all.
• Another theory points out that yawning has nothing to do with tiredness or boredom, but it is the body's way of controlling brain temperature to help us think a little clearer. While both sleep deprivation and exhaustion are found to precede yawning, it doesn't make us ‘more awake’ but instead help keep our brains operating at the right temperature.

• Another notion states that yawning is a way to remove bad air from the lungs. But it seems unlikely that yawning can be beneficial for the respiratory system.
• Another hypothesis is that yawns are caused by the same chemicals (neurotransmitters) in the brain that affect emotions, mood, appetite, and other phenomena.
• But, there's one thing about this involuntary action that everyone knows to be true. Yawning seems contagious - because just by seeing someone else yawns, you'll probably start to do so. Even thinking about it can get you yawning.