Question

what is the cause of yawning

Answer 1

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. ... Certain conditions can cause a vasovagal reaction, which results in excessive yawning.

Answer 2

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. ... Certain conditions can cause a vasovagal reaction, which results in excessiveyawning.