Why is yawning contagious? Here's all the facts about your tired tick.

The average adult yawns about 20 times a day. But why? Surely we can’t all be that tired. The truth is the science behind yawning is much more complex than just a few hours too little sleep.

Even more complex? Why we seem to yawn because other people are yawning. Here are some fast facts on why we yawn and why yawning can be contagious – even between dogs and humans and over the phone.

Why do we yawn?

This reflex occurs most often due to state change, i.e. during periods of transition between waking and sleep. Think of a cartoon character starting their day with a hyperbolically large yawn, complete with outstretched arms and a gaping mouth.

State change isn’t the only known cause though. Research indicates we also yawn to promote alertness, or cortical arousal and sometimes due to increases in brain temperature. So we yawn to wake up and cool down our brains.

Why is yawning contagious?

There are a couple different hypotheses that exist on this. One is that people yawn when other people yawn due to a phenomenon called echopraxia, in which a person sees a certain behavior and, if they’re sensitive to it, will mimic it. This is made possible by mirror neurons in the brain.

Some research indicates it is an evolved form of synchronized group behavior – out of our 20 yawns, many of them occur during shared periods of transition throughout the day. Contagious yawning could also be a tool for increased vigilance. Since yawning can prompt alertness, the idea is that we perhaps evolved to use one another as indicators of when we ourselves should yawn to trigger a more vigilant brain.

When other people yawn we also become more sensitive to our own physiological state – maybe we’re tired and we didn’t know it until someone else’s yawn gives us the trigger we need to notice that.

Is a yawn contagious over the phone?

It can be! Research shows yawning is extra contagious when it comes with a sound effect: that “ahhh” noise a lot of us make. If a person hears that over the airwaves, it might be enough to trigger a sympathetic yawn.

P.S. Even this description might have made you yawn. That's how easily it can spread.

Is yawning contagious to dogs?

If a dog or cat is socialized in the same house as you, cross-species yawning contagion can occur. In fact, lots of other animals also experience contagious yawning. Research shows that it is highly social species that experience this.

What happens if you don’t yawn when someone else does?

Some people are more sensitive to this reflex than others. Recent research suggests that the variability could signal levels of empathy or ability for empathetic processing. This research is supported by the fact that we’re more likely to experience contagious yawning with friends than strangers, and that yawning becomes contagious for us at the age of four or five years old when we begin to understand others' emotions.

There is not yet enough research to definitively prove the relation between sympathetic yawning and empathy, however. In facome scientists believe the explanation could lie somewhere else entirely.