Ann Unick, age 12, of Boardman, Ohio, for her question:

WHAT IS A HALLUCINATION?

A hallucination is a mental state in which a  person sees, hears, tastes, smells or feels something that is not present. A person who experiences a hallucination reacts to some nonpresent stimulus.

often hallucinations may be a symptom of some mental or physical disorder. But normal people also may hear voices or see visions when in solitary confinement or under the influence of drugs.

Hallucinogenic drugs are substances that distort a person's understanding of himself and his surroundings. Scientists hope that perhaps someday the drugs may prove useful to physicians who treat emotional disorders. But they warn that improper use of these drugs could cause serious problems.