Why do we yawn? One theory is that when we are tired we don't inhale deeply enough. As a result we don't take in enough oxygen, become more listless and find it harder to concentrate. So we yawn in order to stimulate the brain by taking in more oxygen. Another hypothesis is that we yawn to cool the brain down and stimulate the flow of blood to the head. Ucenter Dress what to wear for a maternity brides to a wedding
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