Everyone yawns – babies, kids, teenagers, adults. Some birds, reptiles and most mammals also yawn. However, the reason why we yawn is a bit of a mystery. There is also very little research about yawning because for most people yawning is not a problem. Here are a few things that are known about yawns:
The average yawn lasts about six seconds.
Your heart rate can rise as much as 30 percent during a yawn.
55 percent of people will yawn within five minutes of seeing someone else yawn.
In humans, the earliest occurrence of a yawn happens at about 11 weeks after conception – that’s before the baby is born!
Yawns become contagious to people between the first and second years of life.
A part of the brain that plays an important role in yawning is the hypothalamus. Research has shown that some neurotransmitters (for example, dopamine, excitatory amino acids, and nitric oxide) and neuropeptides increase yawning if injected into the hypothalamus of animals.
What’s behind this mysterious epidemic of yawning? Yawning is an involuntary action that causes us to open our mouths wide and breathe in deeply. We know it’s involuntary because we do it even before we are born.
Many people assume that we yawn because our bodies are trying to get rid of extra carbon dioxide and to take in more oxygen. According to this theory, when people are bored or tired, they breathe more slowly. As breathing slows down, less oxygen makes it to the lungs. As carbon dioxide builds up in the blood, a message to the brain results in signals back to the lungs saying, “Take a deep breath,” and a yawn is produced.
It is possible that yawns are contagious because at one time in evolutionary history, the yawn served to coordinate the social behavior of a group of animals. When one member of the group yawned to signal an event, all the other members of the group also yawned. Yawns may still be contagious these days because of a leftover response (a “vestigial” response) that is not used anymore. None of this has been proven true and yawns are still one of the mysteries of the mind.