Since its inception in 1991, the largest and longest-running study of American child-care has generated plenty of controversial — and to many working parents, infuriating — conclusions about the effects on kids of early care outside the family.
The latest findings of the federally funded Early Child Care Research Network are certain to be no exception. At age 15, according to a study being published Friday in the journal Child Development, those who spent long hours in day care as preschoolers are more impulsive and more prone to take risks than are teens whose toddler years were spent largely at home.
The differences between kids who logged long hours in day care and those who did not were slight. When answering questions that measured their impulsiveness, teens rated themselves about 16% more rash in their behavior for every additional 10 hours they spent per week in day care as a preschooler.
In terms of risk-taking, the link to time spent in day care was more marginal: Ten more hours a week in day care prompted the average teen to answer one out of 30 questions with an admission of more risky behavior.
But the study's authors defended the findings as significant and, in some ways, surprising.
For starters, the behavioral differences between day-care veterans and those who spent more time in the care of a parent appeared across the income and class spectrum. Those differences were evident even at 15 years of age — more than a decade after Mom or Dad had picked them up at day care for the last time.
And the effects are spread across vast swaths of the American population: Some 2.3 million children under age 5 go to day-care centers — about a quarter of preschoolers whose mothers are employed, according to the U.S. Census. About 17% are in the care of a nonrelative in family day-care settings and other, less formal arrangements.
That, says psychologist Jay Belsky, an author of the latest study, makes small behavioral shifts potentially far-reaching, especially as preschoolers mature into adolescence and as peers become the preeminent force in a child's life.
"You end up with contagion effects," said Belsky, a professor of psychology at Birkbeck University of London.
In classrooms and peer groups populated by kids who may be just a little more impulsive or risk-taking, "these small effects end up being spread and bounce off each other," said Belsky in an interview. "The dynamic becomes, 'I dare you to take a risk, you dare me to take a risk.'
"Nobody knows what the threshold here is, when the little becomes a lot," he added.
Earlier such warnings from Belsky and other child-care researchers have stirred anxiety and guilt among parents — especially mothers, whose large-scale entry into the workforce spurred an epochal shift in child-care patterns starting in the 1970s.
Belsky said he had been "crucified" for sounding the alarm about the Early Child Care Research Network's earlier findings, which revealed a link between the amount of time a child spent in day care and an increase in aggressive and disobedient behavior throughout elementary school.
He acknowledged that delivering such unwelcome news "can be very politically incorrect" but added that the research, carried out at 21 academic institutions across the country, had gleaned important insights. In doing so, it has helped shift researchers and policymakers from an exclusive focus on the quality of care to consider what Belsky calls the "dosage effect" — or time spent in care.
Deborah Lowe Vandell, the study's lead author, acknowledged that the behavioral effects uncovered among kids with long hours in day care might worry some parents. At the same time, she said, those findings should help give parents, as well as child-care providers and policymakers, some guideposts to ensuring better care for their kids.
"We might be much more attentive to issues of helping children in navigating social settings and in teaching them more about behavioral regulation," said Vandell, a professor of education at UC Irvine. This and other research suggest that smaller group sizes in day-care centers may make it easier for kids to learn important self-control skills, Vandell added.
The latest study results echoed and extended the network's past findings on the importance of good-quality child care — of attentive, trained and well-compensated caregivers, clean facilities and stimulating activities. For teens who had such care, the study found strong advantages in academic performance, and some behavioral benefits too.
But kids reaping those benefits were clearly the exception. Among the 1,364 children enrolled in the study, 60% were considered to have gotten child care of low to moderately low quality, and only 16% got care that was rated highly.