Science Questions

Why are yawns so contagious?

Sun, 27th Jul 2008

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Sandy Fossner asked:

Why are yawns so contagious even from a TV? A graphic designer from Ohio, I listen while at work and find yawns impossible to resist whilst watching them on television.


Helen -  I think you share a trait between about 40 and 60% of people who find yawns very catchable.  The answer is we donít know.  We donít really know why it is that yawns are so contagious.  I think weíre not even quite sure why we yawn anyway! Thereís lots of ideas as to what that is.  Weíre not alone in our catching of yawns.  Chimpanzees do it as well and itís an unconscious process so we really donít know what it is.  It could be early on in evolution we needed to communicate how sleepy we were because it was important for groups of people to go to sleep at the same time and wake up at the same time.  Things like that.  By yawning it created a synchronised behaviour and that sort of thing.  That could be a reason why.

People have actually looked at whatís going on inside our brains when we are catching yawns by putting people inside of magnetic resonance machines and looking at patterns of electricity inside your brain when youíre watching other people yawn.  It hasnít really opened up much of an answer to whatís going on.  We get a lowering in activity of a particular part of the brain called the peri-amygdala region.  This is deactivated very strongly if you have a person who really wants to yawn.  The desire to yawn varies between different people.  Weíre really left with a bit of a question mark on that one.

Although I did rather love some experiments I found a report of which is at a zoo - They wanted to see if this was cross-species so they went round with people looking at animals yawning to see if it made us yawn.  And seeing also if we could make animals yawn by yawning at them.  Unfortunately the answer is no.  Someone claimed they caught a yawn from a lion but I donít know if that really counts!

Chris -  I feel a little bit like yawning with my pets. I have a pet dog and when that yawned I would feel the inclination.

Helen -  Itís possible.  Itís a very peculiar thing because itís not about an open mouth.  If you cover up a yawn itís still contagious.  It seems people are more self-aware and empathetic.  Itís something to do with imagining how that other person youíre looking at is feeling.  We begin yawning in the womb.  We donít know enough about it and why it happens but itís a very good question.  Keep working on it until we find out.

Chris -  Thereís a researcher in New York called Gordon Gallup who did some work on yawns.  He showed students videos of people yawning and looked at who yawned in sympathy.  He then did two things.  He asked the students to breathe through their nose or to breathe with their mouth open or hold a cold compress on their forehead.  Both these strategies, when you hold a cold compress or breathe through the mouth you can effect yawning.  If you breathe through the mouth you yawn more; if you hold a cold compress on your head you yawn less.

His theory is that yawning cools the brain in some way.  Itís to do with alertness.  If you have an infectious yawning behaviour, if you have a group of people who are all sitting round a campfire at night and thereís a danger some predator might come along Ė if one person starts yawning it means one personís getting a little on the tired side.  By cooling the brain and increasing alertness - when you have sleep deprivation brain temperature rises -  this means if everyone catches the yawn everyone is made more alert at once.  This keeps everyone looking for any danger.  This is his theory.


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Sandi Fosnot asked the Naked Scientists: Hello, my name is Sandi. - I'm a graphic designer in Dayton, Ohio and I listen while I work. I have just recently subscribed to your podcast, so I am starting at the very beginning and working my way through to the present ones. So if you have answered my question in a previous podcast, I am sorry. What I would like to know is this: Why are yawns so contagious? If I see someone on TV or hear someone on the radio that yawns, I get this uncontrollable urge to yawn too. I think this is very interesting because it is the only thing that I know of that can be contagious from TV/radio to real life. Please answer my question via email, since I am so behind on the new podcasts and probably won't hear it for quite some time. Thank you so much and I look forward to listening to you guys live when I catch up! Sandi Fosnot What do you think? Sandi Fosnot , Sat, 26th Jul 2008

Easiest to just link to someone elses hard work!

Sean Mahoney SeanMahoney, Wed, 15th Oct 2008

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