Is it true that we yawn when our brains are deprived of oxygen? Most of us can feel a yawn coming on. The muscles in our jaw begin to tighten, our nostrils might flare, and our eyes might tear up ...

Though scientists have put forth various theories for yawning—from fatigue to lack of oxygen—none have held up to scrutiny. "We can put a man on the moon, but we do not understand what the ...

Seeing or hearing someone yawn can make you yawn. This phenomenon is not limited to humans; some animals experience contagious yawning, too. But why is yawning contagious? Brain cells called ...

Humans’ first experience with yawning happens in utero, says Matthew D. Epstein, M.D., associate medical director of the Atlantic Health Sleep Centers in New Jersey. Yet, Earth-side, the ...