Why Do You Yawn When Someone Else Does?

Your body performs many functions that could be considered, well, unusual. Take yawning, for instance. It’s a mostly involuntary reflex brought on by various situations, such as being tired, bored, or even stressed. 

Though the mechanism isn’t fully understood, researchers believe yawning may help wake up your brain by increasing your heart rate, stretching your facial muscles, and reducing your brain’s temperature.

What’s even stranger, though, is that when you see someone yawn, it can trigger you to yawn, too. Even thinking about a yawn can cause one — you may have just yawned while reading this, in fact. Does that mean yawning is contagious? Colds are contagious, but you can’t catch one by reading about it. 

So what exactly makes a yawn — or even the thought of one — cause another yawn?

Copycat Brain Cells

Scientists have been trying to figure out why yawning is “contagious” for decades. One leading theory has to do with mirror neurons. These are specialized brain cells that were first discovered in the 1990s, which can fire when you perform an action as well as when you see someone else do the same thing. 

These neurons tell your brain to “mirror” the actions and emotions of others, and may help us learn from others. There’s still debate about the role mirror neurons play in yawning, but at least one functional magnetic resonance imaging (fMRI) study has shown that when you see someone yawn, the areas of the brain that control social cognition and imitation are activated. 

That means your brain subconsciously mimics the physical action of the yawn you just witnessed. It’s an automatic imitation response known as the “chameleon effect.” Mirror neurons may even be activated simply by reading or thinking about a yawn.

You can see an evolutionary advantage to the phenomenon. If you’re in a hot environment with someone and see them yawn to cool their brain temperature, you probably should be doing the same.

Humans Are Social Creatures

Other scientists, though, think contagious yawning has more to do with socialization and empathy. Social species, including lions, chimpanzees, and domestic dogs, might yawn together to help the group stay alert or shift from resting to waking states. 

Because of this highly social function, whether you mimic a yawn could be influenced by how close you are to the person doing the yawning. A landmark study found that you’re more likely to yawn when you see a relative or friend yawn than an acquaintance or stranger.

According to one 2010 study published by The Royal Society, contagious yawning also doesn’t begin at birth. In the study, it wasn’t observed in children until they were around age 4 or 5, when traits such as empathy — experiencing the emotions of others — become more developed. Not everyone is susceptible to contagious yawning. In studies where people were shown others yawning on video, between 30% and 60% responded by yawning back.

So why are some people less likely to catch yawns than others? Personality traits, empathy levels, intelligence, and genetics could all play a role. One small study found that people with high levels of psychopathic personality traits — including reduced empathy, mimicry, and group cohesion — are less susceptible to yawning contagiously. 

Even after decades of research, why we yawn when someone else does remains a challenge to answer with certainty. While empathy, social bonding, and copycat brain cells are all possible factors, maybe this strange phenomenon is just proof of how deeply connected we are as humans.