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Name: Mark A McLaren
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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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