For instance, the study found that many parents don't know that 1-year-olds can't tell the difference between right and wrong, and often don't cooperate or share when playing with other children.

The results are surprising because the parents who took part in the survey had young children, said lead author Dr. Heather Paradis, a pediatric fellow at the University of Rochester Medical Center, in New York. "They were watching or had just watched their kids go through this development, and they were probably the most knowledgeable of anybody."

Paradis and her colleagues examined the results of a survey of parents -- 98.6 percent of whom were mothers -- of more than 10,000 9-month-old babies. As part of the survey, the parents were asked 11 questions designed to test their knowledge of a baby's development.

The researchers also examined what the parents said about their interactions with their children, and watched videotapes of how the parents taught new things to their kids.

One-third of those surveyed incorrectly answered four or more of the questions. Even when the researchers adjusted the statistics to account for such factors as education levels and income, those parents were still less likely to enjoy "healthy interactions" with their children.

A lack of proper understanding of a child's development can cause assorted problems, Paradis said. For example, she said, a mother might expect an 18-month-old child to sit still for a doctor's appointment, even though children that age are normally curious and like to wander around.

"A mom could misinterpret a child's normal curiosity as intentionally being defiant, and could respond with harsh discipline, withdrawal of affection and repetition of that pattern over time," Paradis said. "That could hinder the child's potential for full growth and development."

The findings were to be presented Sunday at the Pediatric Academic Societies' meeting in Honolulu.

One solution, Paradis said, is for pediatricians to take a more active role in educating new parents. "By improving knowledge of child development among all parents, not just those who are at highest risk, there's an opportunity to enhance parent-child interaction," she said. "It can ultimately lead to better parenting."

Parents can also try to attend "well-child" checkups during the first couple years of life, Paradis said. "We know nationally that only about half of those visits are actually being kept. There's a lot of information relayed to parents during those visits," she noted.

Many pediatric practices "spend a fair amount of time going over issues referred to as 'anticipatory guidance' during a routine well-child checkup," explained Dr. Joseph Gigante, an assistant professor of general pediatrics at Vanderbilt University.

The pediatricians provide information on issues such as nutrition, sleeping habits, growth, development, behavior and safety. "In addition to reviewing these issues during a checkup, parents are often given handouts at the end of each well-child visit that describe what to expect between now and the next visit," he said.

As for future research, Gigante said it would be useful to follow the children of parents with less knowledge about child development "to see how these children do in school and to measure whether or not these children are more at risk for child abuse and neglect."

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