When someone nearby yawns, we often feel as if we've lost bodily control. Our jaws open involuntarily, overcome by some unseen force and compelled to mimic the gaping mouth in our midst. Merely thinking about yawning can cause you to yawn — an unrelenting problem for anyone pondering and writing about the subject.
No one knows for sure what triggers this automatic (and often unconscious) response, but experts have proposed a few theories. Whether simultaneous yawning raises our collective awareness or strengthens our social connections, it certainly seems that the behavior is infectious.