Name: Mark A McLaren
Why do humans and other mammals yawn and why are yawns often contagious?
I'm not entirely sure if this is correct, it is a suggestion
I heard years ago. The premise is that when our bodies sense
that we are nodding off signals are sent to try to 'perk-us-up'.
That signal encourages us to inhale a large volume of air in
an attempt to enrich our blood with oxygen.
As far as why they are 'contagious'... I have never really heard
a theory on this.
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Update: June 2012