We do it more in the morning. We get the urge to do it when we see someone else doing it. And brand spanking new evidence has shown that chimpanzees do it too.
I am, of course, talking about the yawn. Yaaaawwwn. Not only is it one of those words that sound and look ridiculous if you say/write it enough, as I already have, it is also a word that tends to have an effect on people. If you talk to someone about yawning, the chances are that they will yawn at some point. It could just be that you are really boring. It could also be something else.
Do you feel like yawning yet? If not, click here and you soon will. Firstly, the question we should ask is: Why do we yawn? Lots of different suggestions have been proposed, but the answer is that we just do not know. The most popular idea is that yawning allows us to increase the oxygen flow to the brain, but there is actually very little evidence for this theory. Some people think that yawning to opens the tubes in our ears (which allows them to pop, like when we take off in a plane or go through a tunnel at high speed). It has also been suggested that it might help to cool the brain, or that it acts as a signal we have evolved to let others know that we are tired and it’s probably time for everyone to go to bed.
But what’s even more interesting about yawning, is that it is contagious. If you see someone else yawning, there is about a 50% chance that you will yawn yourself, and a high chance that you will at least feel like yawning. Unless you are under the age of 5 years, in which case you are not yet likely to fall for psychologically-induced yawning (Really. Get a toddler to watch this and they won’t even flinch. Those clever kids).
Although lots of animals yawn willy-nilly, it was only fairly recently found that chimpanzees also did this contagious yawning thing: Yawning after watching another chimp yawning. But a new paper published this month has found something even more cool: Chimpanzees are more likely to yawn if they have seen another, familiar chimp yawn. If a chimpanzee sees an individual they know yawning, they are much more likely to yawn themselves. If they see a and a strange chimpanzee they have never seen before yawning, they are much less likely to yawn themselves.
The researchers got two seperate groups of chimpanzees and showed each individual videos of other chimps yawning. These chimps were either members of their own group, or a stranger from the other group who they had never met before. They were much more likely to yawn after watching a member of their own group yawning, but they actually paid more attention to the videos of the chimps they did not know. So they watched videos of the unfamiliar chimps yawning more, but were less likely to show contagious yawning.
What does this mean? Well, contagious yawning has long been linked with empathy. It is thought that individuals who are more empathetic are more likely to yawn after watching someone else yawn. (Most evidence for this comes from the fact that people who score high on empathy tests such as self-recognition and theory of mind are much more likely to display contagious yawning).
The fact that the chimps yawned more when members of their group did rather than when strangers did provides some convincing evidence for this empathy hypothesis. Chimpanzees are highly aggressive, territorial animals and are much nicer to members of their group than to outsiders, and so are more likely to display empathetic behaviours towards them.
It seems that the reason we are so prone to “catching” yawns is down to empathy, and not just that we all need a nap.
And if you got through this post without yawning, I don’t know whether to thank you for your politeness or be concerned at your lack of empathy…
Reference: Campbell M.W. & de Waal F.B.M. (2011) Ingroup-outgroup bias in contagious yawning by chimpanzees supports link to empathy. PLoS ONE, 6(4).