Belsky's work in the late 1980s created a furor when he announced that babies under a year old being cared for by someone other than the mother for more than 20 hours a week are at a greater risk for developing an insecure relationship with their mother and emotional and behavioral problems later in childhood.
"I still believe there are risks associated with early and extensive child care of the kind we know and have in this country," Belsky said. "People have been very critical of me for having said that because the 11th commandment of developmental psychology is 'thou shall not speak ill of day care in America.' "
Clarke-Stewart disagrees with some of Belsky's conclusions.
"I don't think the evidence proves there is a risk," she said. "But in the meantime, I think the strategy should be to go slow and be careful and encourage parents to select and carefully monitor the child, but not put this sort of guilt trip on them" about child care.
Orange County psychologists Adele and Allen Gottfried, who have been studying day care since 1979, say their research has found there is no harm to the youngsters' development.
In fact, they have concluded that the more prestigious the occupations of the parents, the more successful the children are developmentally. The Gottfrieds' work has focused on middle-class families and didn't begin tracking the children until they were a year old.
The child-care study marks the first time that researchers will examine how children's development is affected when their care-givers speak a different language, come from a different culture or have little education.
Although the language difference can be beneficial if the child becomes bilingual, experts say major educational and cultural gaps between the parents and the care-giver can warrant concern, especially when the child starts school.
"If you are well-educated and well-resourced and you are handing your children over to a person who has much less of those things, say nothing of an emotional commitment, that might not be a great exchange for your child, especially if it's for long periods of time," said Belsky.
Leah Heidenrich of Laguna Beach is among those women torn between her desire to pursue her career and provide adequate care for her baby.
Before the birth of her first baby, Heidenrich never doubted her decision to return to work within a year.
"I thought it was important for me to stay home for a while and then go back to work. My career was rewarding. It was necessary financially, and it's what all my peers were doing," she said.
But after baby Spencer turned 6 months old and it came time to resume her career as a librarian and find a nanny to care for her son, Heidenrich began to panic.
"I was almost hysterical when I started interviewing people for the job. I've cried many times," she said. And although she is confident the nanny she hired is loving and conscientious, Heidenrich said she is still troubled over leaving him in the care of another.
"The fact is, my boy will be spending more time with our nanny than with me, and it makes me feel just terrible," said Heidenrich, who works 40 hours a week at Rancho Santiago College in Santa Ana.
"I think anyone with a lick of common sense knows it's better to stay home with your baby," Heidenrich said. "If I could have afforded to take a year off (from work), I would have."
Debra Dietrich, an assistant professor of English at Cal State Fullerton, has a different view. "I was a better mother because I had a life outside the home," she said. Ian, her 14-year-old son, is among the children tracked by the Gottfrieds in their study.
She returned to work when Ian was about 7 months old and believes his development never suffered as a result of her career. If anything, her ability to send him to private schools enhanced his education, she said.
"He is always my primary concern. We have always had quality time together," despite her working full time.
Whether a child benefits from having a stay-at-home mom depends a lot on the mother and her child-rearing techniques, said Mary Ann Sigler, a mother and partner in the firm of Ernst & Young.
"If a mother stays home and all they do is watch television all day, then their children would be much better off in a school setting where they are doing creative things," said Sigler.
Belsky and others agree.
"There is evidence that kids do better in extensive care, for example, if their mothers are depressed or are impoverished and young," said Belsky.
In her book, published this year, Clarke-Stewart points out that some studies have shown that children in day care "are more self-confident, assured, and assertive. . .they are more cooperative. . .self-sufficient and independent of adults."
When they start school, day-care children--especially those who have attended day-care centers or nursery schools--"are better adjusted, more persistent at their tasks, and more likely to be leaders," according to these studies.
But there is another side of the story, Clarke-Stewart says.
These same studies also indicate that children in day care are "sometimes less polite, less agreeable, less compliant with their mother's or care-giver's demands and requests, less respectful of others' rights, more irritable and more rebellious, more likely to use profane language, more boisterous, more competitive. . .than children who have not been in day care."
Moreover, there are a number of studies that have found that kids in day-care centers tend to be more aggressive, Clarke-Stewart said.
"Think big scale," she said. "One of the problems in in this country is a lot of violence. Now think as a solution to it. . .the way would be to put emphasis in day care on teaching kids how to get along."