May 7, 2001 -- They may not listen when told to clean their rooms, but when Mom and Dad are having a raised voices, door-slamming fight, children are all ears.

And what they are hearing isn't good for them, according to a new study from Cardiff University, which says that arguing in front of children can cause them serious damage.

Dr. Gordon Harold, a researcher at Cardiff University in Cardiff, Wales tells Good Morning America's parenting contributor Ann Pleshette Murphy that parents can argue in front of children, but should do so with caution.

"It would be unrealistic to say that, you know, parents should never argue or should never disagree in front of their children," says Harold. "Arguments and disagreements are a natural part of all relationships."

In a three-year study of more than 300 families, researchers showed children films of adults arguing in different ways, and talked to children about their parents' fights. The study finds that even though your argument may have nothing to do with the kids, if you fight the wrong way, it threatens their emotional stability.

Withdrawn or Drawn In

"When children are threatened at an emotional level they're showing increases in negative symptoms such as depression, anxiety, aggression, hostility," Harold says. A child reacting to parental fighting may be withdrawn or quiet, and such behaviors are often overlooked, he says. Or the child may become aggressive and difficult, perhaps even acting out while the parents argue to distract them.

If it does distract them, the child may try it again and again.

But surprisingly, it isn't the number of fights that seems to impact children the most. Instead, the extent to which the parental fighting affects children depends on whether the fights get nasty and whether the parents make up.

His research indicates that verbally or physically aggressive fights, the "silent treatment," intense quarrels and arguments concerned with or involving the child are the worst for children. And all of them are ineffective fights, he says.

"Arguments that are dealt with effectively that are conducted calmly that show clear messages of negotiation and resolution have positive implications for children," Harold says. Part of that boils down to the nature of the parents' relationship with one another.

"We know now, however, that the ability for a parent to parent effectively is determined by the quality of that parent's relationship with their spouse," Harold says. "Couples that are happy and comfortable with each other in their relationship are more emotionally available and sensitive to the children and their needs than couples that are caught up or embroiled in conflict."

Fight the Good Fight

Experts say even though fighting can be damaging to kids, there are good lessons children can learn from fighting.

"When conflicts are handled constructively, kids learn to compromise, compassion, and to use humor and warmth to solve disagreements," Murphy says. "They also learn that conflict with someone you love is not the end of the world."

It isn't necessary for parents to take their fights behind closed doors. For one thing, children can still hear and they aren't easily fooled.

"If mom and dad leave the room happy, have a fight and then come back into the room upset, kids typically will infer that it's something they did to cause their parents' unhappiness," Murphy says.

Research has shown that kids as young as 3 years old pick up on tension between parents. When children are upset by fighting or tension, they may act out or freeze or become very clingy.

The important conclusion of this study is that when a child is acting out or having problems in school, parents are often called in and offered help with their parenting skills. This study shows that it's more important to focus on the couple's relationship with each other, to get the marriage in shape.

Boys and Girls React Differently

When there is conflict between parents, there are differences in how children react depending on their sex: Boys tend to withdraw, and girls try to get involved, Murphy says. This places more of a burden on the children, because they blame themselves if fights continue to flare up.

Murphy offers the following tips for parents:

Count to 10 or leave the room to keep from arguing when you are very upset. If you do get angry, reassure your children by telling them that fights happen, but you do love each other and it's not the children's fault. Make up, but don't fake it. Children will know if you are faking.