Jill Gordan, age 13, of Springfield, I11., for her question:

WHY DO WE YAWN?

When you yawn, you open your mouth wide and take a long, deep breath which you hold for a moment before you breathe out. Your yawn is probably a physiological phenomen used to correct some temporary maladjustment in your body's mechanism.

As you yawn, you may stretch your limbs at the same time. Often one yawning person in a group may set the others yawning. This may be due to suggestion or to the fact that everyone is similarily affected by the environment.

It has been suggested that yawns occur 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.

Although yawning can also be a psychological act associated with mild boredom, it may be an occasional factor in many diseases.