David at 8, seems to the ideal child. He's bright, healthy, good-looking, the hero of his team and the most popular boy in his class.

Yet, David has one problem which worries his mom. He bites his nails.She wonders why. Is it:

- Too much pressure at school?

- The wrong foods?

- Some deep psychological trauma?

- Just a nasty habit?

Mental health experts who work with youngsters say nail-biting is a fairly common habit among 8-year-olds.

"If David's mom took a close look at the hands of her son's friends, she would see that many of them are also nail-biters," says Nathan H. Azrin, professor in the School of Psychology at Nova University in Fort Lauderdale, Fla.

"It does not imply some deep emotional problem in search of physical expression. More likely, it is a distressing habit," says Azrin, 57, who has spent 15 years doing research and writing on nail-biting and other compulsive mannerisms.

Agreeing with that opinion is psychologist Edward R. Christophersen, professor of pediatrics at the University of Kansas Medical Center, Kansas City, Kan., and the Children's Mercy Hospital, Kansas City, Mo., who says, "the one question parents ask me the most often is `Where have I failed?' they didn't fail anywhere. There is not need to feel guilty. Nail-biting is just an unpleasant habit. We all have habits. Some of us bite our nails. Some of us twirl a pen as we talk. Some of us pull out strands of hair. Some play with paper clips."

David's mom can't recall when she first saw David biting his nails.

For some children, it starts as early as age 3 and is a continuation of the thumb-sucking habit, says Azrin, but age 6 is more likely to be the time when parents first notice it. Others don't start biting their nails until their teen years or college.

It may be an expression of nervousness. This is why test-taking time at school can intensify the habit, he says.

It may indicate boredom - a feeling that life lacks sufficiently meaningful activity.

It may be anxiety plus boredom. Waiting for a special phone call is an example.

"It may simply be a child copycatting a sibling or schoolmate," adds Christophersen, 47, who has done 10 years of clinical work in this area.

According to David's mom, it happens during times of relaxation - while watching TV, playing a board game or visiting with a friend.

"Those are all times when David doesn't have both hands occupied and may be sitting in such a position that one hand is near his face or his chin is resting on his hand," says Azrin, who co-authored "Habit Control In a Day," Pocket Books, 1978, with psychologist R. Gregory Nunn.

"The nail-biting starts innocently enough," says Azrin. "One day, the child discovers a chipped or torn nail or a hangnail or a rough cuticle. It brushes against the face or a piece of clothing and it feels uncomfortable. He flicks at it with a thumb or chew it off with his teeth. The nail or cuticle is no longer uncomfortable and he feels better.

"It happens again. He deals with it in the same way, perhaps intertwining the bitting with another activity that brings the hand up to the face such as putting on or straightening eyeglasses, scratching an itching scalp or nose, or resting the chin on a hand. It eventually becomes a part of the child's general mannerisms."

It would be easier to discontinue it, says Azrin, if the child were consciously aware each time he did it, but he often isn't. David isn't, says his mom.

This awareness is often forced on the child by comments or criticisms by parents or friends. By then, however, the nail-biting is so well established, it has become a habit, he says. The child doesn't want to stop, so he engages in it privately to avoid further critical remarks or he does it publicly in such a way as to conceal his actions.

David's mother wants to know what she can do to get him to stop it.

Azrin mentions home remedies that parents have tried.

Bribes: "If you stop biting your nails, I'll bake the brownies you like." Or the reward might be a new computer game, toy, doll, sweater or special outing.

Threats and Punishment: The child is warned he won't be able to go to the movies or a sporting event he is looking forward to if he keeps biting his nails. Other common reactions: A slap, spanking, being "grounded" during a time the child usually plays with friends.

Shame: "You are acting like a baby when you do that."

These solutions are not ideal, says Azrin. In fact, the youngster may view the added attention as a plus and increase the nail-biting.

So what else can a parent try?

"A parent can't do the work for the child," says Azrin. "The child must want to do it himself."

Fortunately, a good many youngsters do. They have an experience where they are embarrassed in front of a boyfriend, girlfriend or classmate by the appearance of their hands. It raises their consciousness to the problem, he says, and they become self-motivated to stop it.

Yet for a few, the problem is allowed to continue to a point where the nails are gnawed away, the tissue is damaged and the fingers are bleeding and scabbed.

David's mother wonders if one of those bitter solutions commercially available at drug stores would work.

"No," says Azrin. "They wash off easily. The do not motivate the child to stop."

But Christophersen disagrees. "They work if used in a very specific way. For one full week, make it a point to spend more time with your child. Keep these interactions pleasant and unrelated to the nail-biting. Then set aside two days - Friday evening through Sunday evening usually work best - when you can concentrate on the child's habit. Brush the solution on his nails. Each and every time he puts his nails to his lips or washes his hands or takes a bath, replace the substance on the nails. In very little time, the problem is eliminated."

Azrin recommends these eight steps. The nail-biting should decrease after a day, even more after a week, he says, and be gone in six months or less.

1. Ask your child to think of times or episodes when others expressed disgust and he was embarrassed and wished there was not a nail-biting problem. Let him describe these situations. In this way, says Azrin, the child learns that control of the habit is in his own best interest. It creates self-motivation.

2. Raise your child's awareness. Let him stand in front of a mirror and go through the steps leading up to nail-biting so he can see how it looks to others.

3. Suggest to your child constructive activities to keep the hands busy when he has the urge to bite his nails. Azrin calls these "competing reactions." (See related story on this page.)

4. Let your child play-act situations in which he is likely to bite his nails and rehearse the substitute activities _ the competing reactions.

5. Practice, practice, practice the competing reactions.

6. When you see your child biting his nails, mention it, but don't be a nag, don't criticize. Be polite, positive. Azrin gives an example: "Here's a poem and note pad for you to hold while you are on the phone." That's much more constructive than saying "Oh no, do you have to bite your nails when you talk on the phone?"

7. Enlist the support of family and friends to help increase awareness and to offer encouragement.

8. Buy your child a manicure kit or emery board, scissors and clippers which he can carry with him at all times.

Within six months, the competing reactions should be automatic, and the nail-biting should be gone, says Azrin.

Some parents find that their child raises his hand more at school, plays more board games and writes without concealing his fingers in a cramped position.

If your nail-biter is a girl, she may become more interested in nail polish, rings and braclets, Azrin says.

You might celebrate by giving your child a new watch, bracelet or ring, he says.

However, if the nail-biting persists, says this therapist, it is now time to examine the child's diet, to talk with his teachers about possible stress at school, or to see a psychologist to determine where there is a personal problem that the child is unwilling or unable to verbalize.

Azrin became interested in nail-biting in the early 1970s while director of the Department of Treatment Development at the Anna Mental Health and Developmental Center, a state mental hospital in Anna, Ill.

He was studying patients with nervous muscular tics, such as eye twitches and shoulder and head jerking, which involve a small group of muscles. His patients were taught to engage in an alternative movement which was incompatible with the tic movement. The nervous tic disappeared _ his competing reaction theory worked.

He wondered whether there were competing reactions that could interfere with nail-biting and bring that compulsion to a halt.

He put notices in Illinois newspapers asking for volunteers. Close to 300 replied, from age 6 to over 60.

Each volunteer had a two-hour private session with Azrin or associate R. Gregory Nunn or another member of the research team. They talked about nail-biting episodes that had caused embarrassment, inconvenience or annoyance. They stood in front of a mirror and saw how it looked when they went through the stages leading up to nail-biting _ slowly rubbing the nail with the thumb and feeling the roughness for several seconds, starting to bring the hand up to the face _ then biting the nail. They kept track of their nail-biting in a daily diary. They were instructed in alternative activities _ competing reactions _ and had a chance to practice them.

Study volunteers kept in touch with the research team by phone and mail. The conditions showed great improvement within a day, more within a week and a success rate of 99.5 percent within six months.

Now at Nova University, Azrin is still actively conducting research on compulsive habits and has taken the competing reaction theory one step further by applying it to those afflicted with Tourette's Syndrome _ a biologically based condition involving the presence of a large number of tics in the same individual.

(C) 1988 Barbara Burtoff Syndicated Features

Barbara Burtoff is a syndicated writer based in Washington, D.C.