Debbie Eyears, age 17, of Sarasota, Fla., for her question:

WHAT CAUSES A YAWN?

Yawning can be brought on by drowsiness, fatigue or boredom. Sometimes when one person yawns, others in the group may yawn, too. This may be due to suggestion or to the fact that everyone in the group is similarly affected by the environment.

Yawning is probably a physiological phenomenon to correct some temporary condition in the body. Some doctors say it happens when the circulation of the blood in the brain is not sufficient to maintain an alert state. Yawning improves the flow of blood back to the heart, which will be followed by an increased output of blood and an improved blood supply to the brain.

When you yawn, you open your mouth wide and take a long, deep breath which you hold for a moment. Often you stretch your arms and legs at the same time.