What influences how you react to your children?

We know that parents who have been abused by their own parents or caretakers are more likely to abuse their own children than are parents who were not abused. There also are behavioral patterns that seem to recur in some families more than others.

We are far more willing to attribute physical patterns that recur, such as a distinctive shade of blue eyes, to genetic influences than we are willing to attribute behavior patterns to them. Figuring out the source of behavior has been one of the most controversial aspects of all the nature/nurture debates.

Involved in this quest is David Rowe, a behavioral geneticist at the University of Arizona in Tucson and the author of "The Limits of Family Influence." He was one of the experts who presented findings at last week's conference on "Parenting and the Child's World," sponsored by the National Institute of Child Health and Human Development and the Robert Wood Johnson Foundation.

He and his colleagues did a study of three types of adult siblings raising children under the age of 8. The adults they studied were identical twins, fraternal twins and adopted siblings. "The genetic expectation is that if genes influence parenting styles, the identical twin siblings should parent more alike than the fraternal, and both should parent more alike than the adoptive siblings," Rowe says. The environmentalist school of thinking believes that you learn parenting by observing your own parents, which would mean "then, the siblings should parent somewhat alike but genetics should have no consequence."

The result of the study, he said, is that there is a genetic influence on parenting. "The identical twins parented most alike, the fraternal twins were in the middle, and with the adoptive siblings, you get a big contrast. One might be very warm and the other very aloof," he says. "The genetic influences come about because our personality traits influence how we parent. Warm and affectionate parents are more often extroverted, outgoing people. They are more emotionally stable kinds of people.

"We know there are genetic influences on personality," he says, particularly on these five traits: extroversion, emotional stability, agreeableness, conscientiousness and intellectual interest, "which overlaps with intellectual ability."

But behavior between parents and children is not unilateral, and there is a large body of research that shows that an infant who wins parental attention with an activity such as smiling or crying will be inclined to repeat that activity. "Children elicit parenting behavior," Rowe says. "A highly active child that breaks toys and runs around" and might endanger himself will provoke much more vigilant behavior in parents than will the more sedentary child. "This is especially true of children who have problems. Difficult children receive harsh discipline because they are harder to parent. A parent can look very good when the first child is easy, and then the second child comes along and is not so easy, and you don't look so good anymore."

He cites the findings of the Colorado Adoption Project that defined some adopted children as high-risk children based on the impulsive, minor delinquent behavior of their biological mothers. "These are all babies adopted very early," Rowe says, and the question was whether they received different parenting from their adoptive parents, who knew nothing of their biological mother's "antisocial" behavior, than other adopted children did from their adoptive parents. "The result was that the adoptive parents meted out more harsh discipline to the difficult children, the ones with the biological background suggesting they will be difficult. Children come into a family, and they evoke a different parenting style. You should never think of parenting as parent influence on child alone but also the child on the parent. This has not been given enough emphasis. Parents who have more than one child will recognize how different children evoke different behaviors from them."

In another study, this one of adolescent twins, Rowe found that the identical twins reported much more similarity in such things as the warmth their parents showed them, than did fraternal twins, which again underscores the impact the child has on how he is parented.

"I think parents overestimate their influence," says Rowe, who has one child. "The kinds of characteristics that children develop in the long run depend much more on the nature of the child than the nurture that child receives. I like to tell parents to relax more, but I've never been able to do that."

Rowe is one of the researchers working with the National Longitudinal Study of Adolescent Health, which has more than 3,000 pairs of identical twins, fraternal twins, siblings, half siblings and unrelated young people ages 14 to 18 in its sample. "We did a genetic study of aggression and found . . . a modest genetic influence." Further, he says, "there is a tendency for higher levels of aggression in all schools that were ethnically diverse, which is not too surprising, but a little discouraging. Kids are in different cliques, and there are conflicts between them."

Another window into whether the environment or genetics shapes behavior came from looking at smoking behavior in siblings. While starting to smoke is influenced by peers, genetics influence addiction levels. "Fraternal are as alike as identical twins," he said. "The smoking result is interesting because the amount of smoking they do once addicted seems to depend pretty strongly on genetics." If parents are heavy smokers, their children tend to smoke more heavily. His advice to parents is one we have heard before, but his research makes it all the more compelling, particularly for parents who are heavy smokers: "You want to stop that first cigarette if you can." Raising a teenager who smokes is one area where parents have an impact.