Why do we open our mouths when shocked?

18 March 2014


Meera looking surprised



We use the expression "open mouthed" to describe an astounded response, usually to a dramatic unexpected event. This can be seen in that fabulous video of "Holland's Got Talent," when a nine-year-old girl blows the audience away with her beautiful voice, rendering the three judges literally "open-mouthed." You can view it at:
That being said, why do people instinctively gape with open mouths when confronted when astonished or amazed?
Look forward to your response.
John Gamel
P. S. Keep up the great work. I never miss a podcast.


Ginny - So, emotions are a really interesting thing and if you think about them evolutionarily, the point of emotions and the point of the facial expressions we make when we're expressing emotions is to communicate with other people. So, there's been some interesting research that goes back as far as Darwin and more recently, Paul Ekman who actually looked at people around the world and how they express different emotions. And they found that there were some basic emotions that are expressed in basically the same way. So, wherever you go in the world, if someone's angry, they'll sort furrow their brow and maybe bare their teeth. If they're fearful, they'll widen their eyes and possibly open their mouth. I think surprise probably is linked to fear a bit. So, it could just be that these emotions, we all have to do the same thing because that's the only way that we'll know what the other person is feeling. Another idea for why exactly surprise is an open mouth could be that it is sort of a subset of fear. When you're fearful, what your body does is it tries to prepare to deal with the thing that's frightening you. So, it prepares to either run away or fight - the 'flight or fight' response. In doing that, one of the things that it needs is more oxygen because it needs to prepare your muscles to either fight or to run away. So, opening your mouth and sort of taking a big breath is going to get lots of oxygen into your blood and might help deal with that. And widening your eyes hopefully gets more light in so you can see better. So, it could be all related to that sort of thing.


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