Seeing someone yawn is all it takes

to get me yawning.

In fact seeing someone yawn or hearing the word

or reading the word

is enough to get half of healthy adults yawning

Are you yawning now?

Yawning is an example of emotional contagion,

a phenomenon in which we tend to share

the feelings of the people around us

Of course yawning isn't the only behavior

that's contagious.

Sitcoms use laugh tracks because hearing

other people laugh can be hard to resist

(Laughter)

Even if the show isn't funny.

And when a baby in a hospital starts crying

look out,

because others within earshot

will also start crying.

We also copy less obvious signals from other people

such as posture,

speech patterns and facial expressions.

Emotional contagion and mimicry

may form the basis of empathy.

They help us to intuit the thoughts

and feelings of the people in our social circle.

And children under four

are actually less prone to contagious yawning,

as are children and adolescents on the autism spectrum.

Faces tell us a lot about what others are thinking and feeling

and people with autism tend to focus less on faces

and miss a lot of important social cues.

But even youngsters with autism

start to yawn when they're coaxed

into looking at the eyes

and sometimes the mouth of a yawner.

Evidence from chimpanzees suggests that yawning

spreads when empathy exists between two chimps.

Scientists showed chimps videos of either familiar animals

or strangers yawning.

The observers were much more likely to yawn

when they saw a familiar chimp.

We feel more empathy for people in our social groups

than for strangers.

And the brain mechanisms that support

contagious yawning may help maintain relationships too.

Even though it can be annoying,

contagious yawning is probably a sign of good social skills.

So don't hold back on the yawns.

Your friends might thank you for it.

For Scientific American's Instant Egghead

(Yawn)

I'm Sandra Upson.