What Causes Excessive Yawning? Yawning is a mostly involuntary process of opening the mouth and breathing in deeply, filling the lungs with air. It is a very natural response to being tired. In fact, yawning is usually triggered by sleepiness or fatigue. Some yawns are short, and some last for several seconds before an open-mouthed exhale. Watery eyes, stretching, or audible sighs may accompany yawning. Researchers aren’t exactly sure why yawning occurs, but common…"Aah: Excessive Yawning"