Why is yawning contagious?

[james dean]

if you see someone yawn, you immediatly yawn aswell. what would happen of evryone in th eworld stood in a straight line and did? would the last in the line die of lack of oxygen?

[Cetti]

Here's a good explanation:

question 13283

[nona suomy]

That all makes very good sense but I have had a good laugh in the past by saying it to people and watching them yawn. It seems the power of suggestion is enough to set people off - weird!

[nona suomy]

That all makes very good sense but I have had a good laugh in the past by saying it to people and watching them yawn. It seems the power of suggestion is enough to set people off - weird!

[andy hughes]

The primitive hangover argument sounds feasible - the 'extra oxygen' one no longer appears valid, for the simple reason that foetus' yawn in the womb and they are not breathing oxygen, so no need to increase a non-existent intake.

[Tintin19]

How many people yawned whilst reading this? ;-D

[Barquentine]

Yep, I yawned as I was reading the question! I've just yawned again while typing this reply!! Oh no - now I can't stop. I even yawn when I see my cat yawning - how weird is that?! And why is it that when I feel a sneeze coming - if I look towards a bright light it makes me sneeze staightaway? My Mum and Dad used to do the same but not many people seem to know that it does work.