Researchers initially thought that yawning might mean you lack oxygen, but more recent evidence suggests this is untrue.

Excessive yawning reasons include: Physical Causes—Fatigue, general tiredness, body temperature malfunctions, and stimulation of the vagus nerve can cause frequent yawning. Excessive yawning and sleep disorders are often correlated. Emotional Causes—Anxiety and depression can lead to yawning excessively.

Thus, contrary to our impression that yawning is rude and insulting, Dr. Gallup asserts that “yawning is really a compliment, because it suggests that brain mechanisms have kicked in to reinstate and optimize mental processing.”