What's a working parent to do? That's the cry that rose from households across the country last month with the release of preliminary findings from an ongoing National Institutes of Health study of more than 1,300 youngsters 4½ to 5½ years old. The study found that those who spent 30 hours a week or more in childcare tended to show more behavioral problems such as aggression than those who stayed home with their mothers. This disturbing news was announced by one of the study's 13 principal investigators, University of London professor of psychology Jay Belsky, who went on to recommend that parents cut back on work hours. Yet a few days later, other members of his own research team—mainly women—spoke out, contending that Belsky had oversimplified the data and failed to address other variables that might encourage aggressiveness.

One of the most vocal has been child psychologist Kathleen McCartney, a professor at the Harvard Graduate School of Education who helped launch the study a decade ago. McCartney, 46, is the mother of two teenage daughters—Kaitlin, 19, a freshman at Middlebury College, and Kimberly, 15, a freshman at Philips Exeter Academy—and a pair of older stepsons from her second marriage. She is also the former director of an on-campus childcare center at the University of New Hampshire. "Like all moms using childcare, I had my moments of crisis," she says. "But I was able to observe firsthand how children can thrive when they are around adults who care for them." McCartney met with national correspondent Joanne Fowler to discuss the study's controversial results.

What do you believe are your study's key findings?

Parents still play the most important role in their children's development—that's the major predictor of how well children do socially and cognitively. Our second most significant finding concerns the quality of interaction between childcare providers and children. When quality is high, children do better on tests of intellectual development, school readiness and vocabulary and have fewer behavior problems.

So you don't believe that children in daycare are more prone to aggression?

The proportion of kids who showed behavioral problems—for instance, destroyed other kids' property, hit, talked a lot—was 17 percent. But there's no cause for alarm; that's the same rate observed in kids at large. Nevertheless, only 5 percent of 4-year-olds who stayed home with their mothers showed behavioral problems. By the time those kids reached kindergarten, the rate increased to 9 percent. It's still a mystery why the percentages are significantly different. It might have to do with peer exposure. It could also be that parents of children who are difficult may choose to put them in childcare because they are difficult. But remember, 83 percent of kids in childcare are doing just fine.

Doesn't the quality of maternal care vary as widely as the quality of childcare?

Yes. We observed a wide range of sensitivity and interactive abilities among mothers. And we found that maternal depression is one of the strongest predictors of children's behavioral problems regardless of whether the child is in daycare. Such mothers are not as responsive to their children's needs.

So staying at home with Mom isn't always better for the child?

That's right. Some kids are cared for well at home and some aren't. Some childcare centers are fabulous, some are mediocre, and some aren't very good at all.

What are the bad ones like?

High staff turnover, caregivers who interact harshly with children or don't care about them. A lack of curriculum and too few caregivers for the number of children are also indicators.

Can good childcare have benefits for youngsters?

Children in quality childcare tested better than those in low quality childcare in general on short-term memory, comprehension and vocabulary because caregivers there implement a curriculum to prepare the children for school. These youngsters also tend to be more socially competent. On the other hand, children in care settings with a lot of TV watching scored lower on cognitive tests.

Do you think moms need to spend more time at home with kids?

Not necessarily. They should improve the quality of time they spend with their kids and make sure that their children are in quality childcare. I don't think parents need to cut back work hours unless they're excessive.

Are first-rate childcare centers typically more expensive?

Yes. Quality care costs more to the parents, and the teachers are paid more. We know from other studies that when you pay people better, you get better people.

What should parents look for in a childcare provider?

Find a childcare provider whose values on child rearing mirror your own. That requires hanging out and taking the time to watch the provider in action with children. Ask the childcare provider or center director if they are licensed, or accredited by the National Association for the Education of Young Children. Is their staff-to-child ratio low? Are the teachers trained in early education? Also check into health precautions.

With 65 percent of U.S. mothers with children under 6 working, finding the best childcare is a pressing concern; how can it be improved?

Right now we primarily have support for those in poverty, with Head Start. For the middle class there's a tax credit of $480 a year for one child, $960 for two children—but the average annual cost of childcare runs from $4,000 to more than $10,000, with the tab for a full-time nanny in New York City running upwards of $1,600 a month. What surprises me is that more working people don't ask for the support they need; part of the reason is the guilt we still feel. My opinion is that we need a greater investment in childcare for all children. I think childcare should be a public responsibility.