Why Are Yawns Contagious?

First, it should be stated that many of us have been yawning since we were in the womb. Also, humans are not the only creatures who yawn. Chimpanzees do it, dogs do it, birds do it and even fish do it.

But why all the yawning?

One theory, backed by research, states that we yawn to cool our brains. Brains use up 40% of the body's metabolic energy and, consequently, get pretty hot. When we yawn, we stretch the jaw muscles and increase blood flow to the head, as we increase air into the sinus passages, mouth and nasal cavities. Cooler blood goes up to the brain and warmer blood goes down into the body. Cool air is inhaled and warm air is exhaled.

One study found that 41% of people who put a warm pack on their heads before watching a video of people yawning, yawned contagiously; only 9% of those in the study who put a cold pack on their heads yawned when watching the video.

Similarly, a study using mice showed that before yawning, the mice brain temperatures were higher and after yawning their brain temperatures were lower.

More evidence is found in the fact that we yawn before going to bed and also as we wake up in the morning. Our brain and body temperatures are at their highest just before we fall asleep; as we fall asleep, the temperatures decline. And, as we wake up, the temperatures start to rise again quickly. It's reasonable to say that we are cooling our brains before we go to sleep and after we wake up and this accounts for why we yawn at those times.

One very convincing theory, backed by research, is that we yawn when others yawn out of empathy. We put ourselves in another person's shoes by feeling what they feel. So, when they cry, we are liable to cry; when they laugh, we might laugh. When they yawn, we are likely to yawn.

Researchers have connected this, also, to social bonding. People would look to the group to stay alert. It has been shown that yawning is used in anticipation of events and for transitions. Seeing a member of the group prepare in such a way could make others in the group follow suit.

This is backed up by certain physiological changes that the body goes through during yawning.

That empathy plays a role in contagious yawning is also supported by studies using MRI scans that showed that, when this yawning occurred in subjects, the part of the brain that helps us feel what others feel was activated.

What is equally interesting and relevant is who yawns contagiously. It doesn't seem to occur with great frequency until the age of 4. Also, people with severe autism do not yawn just because someone else yawns.

This has led some researchers to seriously consider biological reasons for contagious yawning, considering, also, the possibilities of finding an answer to such conditions as autism and schizophrenia.

Fact is, it's still a mystery exactly why we yawn when other people yawn. There is strong evidence pointing to old hard-wired empathy and some evidence pointing to biological reasons for why yawns are contagious for most of us. But none of it proves totally that we are yawning when someone else yawns for either of those reasons.

Are we just copy-cats? Well, even if we are, mimicking yawning might point to other reasons for mimicking. There is reason to believe that some empathy is rooted in mimicking; for instance, feeling what someone else feels so that you can empathize with them.

As stated, some people with conditions that make their brain and neurological systems different, like those with autism, show signs that, for them, yawns are not contagious. Is there something different in their brains that makes them not yawn when you yawn? Could be.

Researchers' interest in this subject has been piqued by their previous studies on the subject, so it is very possible in the future we will learn more about why yawns are contagious and might even discover exactly what's going on with autism.

Until then, we will just have to accept the fact that we yawn uncontrollably when people around us yawn, and enjoy the cooling of our brains in the meantime.