Mom is summoned to the playroom by a muffled scream. She yanks open the toy box lid to find a hysterical toddler crouched inside. Before she can finish demanding an explanation, 3-year-old big brother has denied all. "I didn't do it! He got stuck in there looking for MY blocks!"

That is today's story. Last week it was a victimless crime. The boy described a special drawing he did for his mother at preschool. But, according to his teacher, the child refuses to draw.

Here is a seemingly happy 3-year-old making up what he does in a day. It's alarming when young children behave like adults, blurting out cover-ups, exaggerating successes, indelicately sidestepping the truth. Despite the regular dependence many adults have on "little white lies," most parents feel something akin to moral outrage when their children don't tell the truth. Whether it's secretly overpowering baby brother or "losing" a rotten report card, all kids experiment with reshuffling the facts.

What should parents do when it starts, when your child who is still learning to talk, is simultaneously learning to lie?

Control yourself, experts say. Abandon your impulse to blow up and demand the truth, or to promise your child no one will ever trust a liar. Try viewing the world from a child's perspective, says Dr. Lawrence Balter, a New York child psychologist and host of a syndicated radio call-in program for parents. Like most psychologists, Balter rejects the term "lie" as too pejorative for the youngest offenders.

"I don't think the term lying applies to children under the age of 5 or so," says Balter. "Up to about that age you can't depend on a child for reliable information because emotional reactions color perception much more than with adults. Kids can truly believe what they're saying because they feel something so strongly."

Little Sally watched a friend fall and cut himself on the school playground. That night she told her parents her friend had bashed his head and blood was everywhere. In fact, the boy only needed a bandage.

One of the tasks of the preschool years is to distinguish between fantasy and reality. During this stage of development it's entirely possible that elephants talk, the sky produces angels and there is a hairy monster in the basement. "A 3- or 4-year-old is reliable in the sense that she will report how she experiences things through her eyes," says Dr. Robert Brooks, clinical psychologist at McLean Hospital outside Boston. "For her it's reliable, for {adults} it may not be the most accurate picture." A child's colorful chatter is packed full of fanciful images, and experts agree that when kids spin tall tales it's a way of exercising their intellectual muscle. Being a great storyteller is often the mark of a smart kid, says Brooks. "Having fantasies and imaginary friends is wonderful for young kids, if it doesn't consume their lives. It's a very important part of child development."

Much childish fibbing, however, is simply done to avoid trouble. Denying wrongdoing is a very normal survival tactic, but parental response in the early years will help determine if it becomes a pattern of denial later on. While children of any age should be shown that telling the truth is important, Washington child psychologist Neil Bernstein suggests the punishment be immediate, brief, and appropriate for the age of the child.

"Be concrete with a 3-year-old; don't go on about the value of honesty because it's an abstraction that is lost on this age group. Show them directly when they aren't telling you the truth. 'Is the toothpaste open? No. Is the toothbrush wet? No. You didn't brush your teeth, so do it now.' "

Demanding confessions is one way parents inadvertently set kids up for lying, says Bernstein. "If it's obvious what's happened, cookie crumbs all over, chocolate on the face, jar lid on the counter, what's so important about getting the child to admit he took a cookie? If it's obvious the child fibbed, don't barter with him. Have an immediate consequence and get the punishment over with."

If a confession is volunteered, recognize the Herculean effort it took to tell the truth, instead of reacting with the anger you might be feeling. In her book, The Child Care Encyclopedia (Alfred A. Knopf, $22.95), author Penelope Leach writes, "If every confession is met by overwhelming anger, the child would be pretty stupid to carry on with it."

Once children know the difference between reality and fantasy, yet lying seems constant, it should raise a red flag. If a child is never able to admit to a falsehood or appears to be unable to see it even given incontrovertible evidence, then, it's time to ask, why does my child bother to lie?

"If kids are constantly saying 'I didn't do it,' you have to consider how you're coming across to your child," says Brooks. "If denial is very predictable, he may be experiencing you as more strict than you think. In your efforts to crack down, there might be loss of trust developing."

There might also be fearfully high expectations coming across. Many children, rather than submit to feeling bad about letting their parents down, will boast about accomplishments that never happen. Self-aggrandizing stories can reflect low self-esteem in any age youngster:

Four-year-old Mary promised her parents that she wrote the whole alphabet at preschool, then said she just didn't feel like showing them her work. Mark, 12, bragged to his friends that his family was going to Europe when in fact they had planned a vacation at Ocean City.

These kinds of fabrications can also be a cry for help with something that is going on in the child's world that he is trying to change by lying.

Sadly, there are the rare occasions when a child will describe something that happened to her, which a parent may not want to believe. In child abuse cases, parents are advised by experts to consider the details a child provides. "If a child says someone did something to me that is otherwise out of her realm of experience, you have to assume it's the truth," says Dr. Balter. "Most 4-year-olds don't know details of anatomy, for example."

The most conscientious parents can be overlooking one of the simplest approaches to the problem of lying: Listening. Busy lives have squeezed out time for just shooting the breeze with a child. It's those times, says Cecil Clark, clinical psychologist at the Human Development Center in Bethesda, when kids feel safe to volunteer what's on their minds.

"We should always try to listen to children, because even if what's being said is not totally accurate, they will reveal much of what they care about," Clark says. He advocates a ritual of listening. "Bedtime is great for this. It's the one time in the day when parents have a little leverage, because most kids fight off sleep. Let your child talk."

It is, of course, impossible to listen if you're attempting to scare your child into telling you the truth. Eliciting fear never promotes honesty from the accused, only more creative tactics on their part for avoiding you, the truth and the terrible punishment that awaits if the truth is told.

In attempting to listen, parents have a habit of denying what they hear. "You don't mean that," is the kind of response that cuts out parental acceptance of true feelings and is almost asking a child to lie. Interrogating kids also doesn't work, partly because it's often intimidating, and also because children have a hard time assigning words to feelings.

Children don't answer direct questions nearly as well as they communicate through play. "Very often a child will use animals, dolls, friends to act out what's on his mind. It's a time when kids unconsciously express what concerns, worries or interests them," says Clark.

Hard as it may be for parents to admit, kids learn to lie where they learn many things: at home. Kids see parents refusing invitations on phony grounds, offering fake compliments, ducking out of commitments on false pretenses. One psychologist used a personal example: "Last night I was reading to my 4-year-old boy. I got up and said I had to go to the bathroom. My son immediately called me on it and said, 'Daddy, you're not going to the bathroom. You're just leaving.' "

The rule is, parents set the standards for kids about telling the truth through their own behavior, no matter how much they preach about the virtues of honesty. Rhoda Duncan is an Alexandria free-lance writer.