Shelly Milne, age 11, of Bountiful, Utah, for her question:

WHAT CAUSES HICCUPS?

We hiccup when there is a spasm or involuntary movement of the diaphragm, the muscular partition that separates the abdominal cavity from the chest cavity. That's what happens but we don't know why it happens.

The hiccup spasm causes us to draw in air, or inspire. The opening between the vocal cords is shut off suddenly, producing, the " hic. " Control of the diaphragm is by the right and left phrenic nerves, but we don't know why they send impulses to produce the apparently useless action.

The hiccup spasm series usually ends as mysteriously and as fast as it started.