Why is yawning contagious?

It's something we do all the time, everyday in fact! But why do we yawn? And what is a yawn? Do animals yawn too! Find out everything you ever wanted to know about yawning in our in-depth blog including the 4 most common theories about why we yawn.

What is a yawn?
Why are yawns contagious?
The physiological theory
The evolution theory
The boredom theory
The brain-cooling theory
Do dogs yawn?
Yawning, in conclusion

What is a yawn?

‘A yawn is a reflex consisting of the simultaneous inhalation of air and the stretching of the eardrums, followed by an exhalation of breath. Yawning (oscitation) most often occurs in adults immediately before and after sleep, during tedious activities and as a result of its contagious quality;’ according to Wikipedia.

Contagious yawning is a common form of 'echo-phenomena'. This is the automatic imitation of another's words (echolalia) or actions (echopraxia). Which is also related to other health conditions like epilepsy, dementia, autism and Tourette syndrome - all linked to cortical excitability and/or decreased physiological inhibition.

Next time you're in a meeting, try this little experiment: Take a big yawn, cover your mouth out of courtesy and watch to see how many people follow suit. There's a good chance you'll set off a chain reaction of deep breaths and wide-open mouths. And before you finish reading this, it's likely you'll yawn at least once. Just reading about yawning will make you do it, just as seeing or hearing someone else yawn makes us do it, too.

Why are yawns contagious?

Experts believe that yawning is a sign of empathy and therefore contagious in the same way that you might smile or frown if the person you're looking at smiles or frowns at you. So, if one person yawns, almost everyone close by will also yawn.

Yawning is an involuntary action that causes us to open our mouths wide and breathe in deeply. Many parts of the body are in action when you yawn. First, your mouth opens and your jaw drops, allowing as much air as possible to be taken in. 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 4 most common theories about why we yawn:

1. The physiological theory

Our bodies induce yawning to draw in more oxygen or remove a build up of carbon dioxide. This theory helps explain why we yawn in groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen and get rid of the excess carbon dioxide. However, if our bodies make us yawn to draw in needed oxygen, wouldn't we yawn during exercise? Robert Provine, a developmental neuroscientist at the University of Maryland, Baltimore County and a leading expert on yawning, has tested this theory: 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 [source: University of Washington].

2. The evolution theory

Some think that yawning began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities [source: University of Washington].

3. The boredom theory

Although we do tend to yawn when bored or tired, this theory doesn't explain why Olympic athletes yawn right before they compete in their event or why dogs tend to yawn just before they attack. It's doubtful that either is bored [source: Patterson.]

4. The brain-cooling theory

A more recent theory proposed by researchers is that since people yawn more in situations where their brains are likely to be warmer - tested by having some subjects breathe through their noses or press hot or cold packs to their foreheads - it's a way to cool down their brains. Why does it matter if our brains are cold or hot? Apparently, cool brains can think more clearly; hence, yawning might have developed to help keep us alert [source: Nagourney].

Do dogs yawn?

Yes, dogs do yawn! Interestingly, while all vertebrates (including fish) yawn, only humans, chimps and possibly dogs find yawns contagious. And people don't find them contagious until they're about 4 years old. Recent studies show that contagious yawning may be linked to one's capacity for empathy [source: Sohn].

In one study, autistic and non-autistic children were shown videos of people yawning and people simply moving their mouths. Both groups of kids yawned the same amount when viewing the video of people moving their mouths. But the non-autistic kids yawned much more frequently than those with autism when watching people really yawning. Since autism is a disorder that affects a person's social interaction skills, including the ability to empathize with others, the autistic kids' lack of yawning when watching others do so could indicate that they're less empathetic. The study also found the more severe a child's autism, the less likely he or she was to yawn. On a positive note, one day doctors may be able to diagnose cognitive disabilities in young children more easily by seeing whether or not they can catch a yawn from others [sources: Kahn, Sohn].