PRINCETON, N.J.—In a study of 14,000 U.S. children, 40 percent lack strong emotional bonds — what psychologists call "secure attachment" — with their parents that are crucial to success later in life, according to a new report. The researchers found that these children are more likely to face educational and behavioral problems.

In a report published by Sutton Trust, a London-based institute that has published more than 140 research papers on education and social mobility, researchers from Princeton University, Columbia University, the London School of Economics and Political Science and the University of Bristol found that infants under the age of three who do not form strong bonds with their mothers or fathers are more likely to be aggressive, defiant and hyperactive as adults. These bonds, or secure attachments, are formed through early parental care, such as picking up a child when he or she cries or holding and reassuring a child.

"When parents tune in to and respond to their children's needs and are a dependable source of comfort, those children learn how to manage their own feeling and behaviors," said Sophie Moullin, a joint doctoral candidate studying at Princeton's Department of Sociology and the Office of Population Research, which is based at the Woodrow Wilson School of Public and International Affairs. "These secure attachments to their mothers and fathers provide these children with a base from which they can thrive."

Written by Moullin, Jane Waldfogel from Columbia University and the London School of Economics and Political Science and Elizabeth Washbrook from the University of Bristol, the report uses data collected by the Early Childhood Longitudinal Study, a nationally representative U.S. study of 14,000 children born in 2001. The researchers also reviewed more than 100 academic studies.

Their analysis shows that about 60 percent of children develop strong attachments to their parents, which are formed through simple actions, such as holding a baby lovingly and responding to the baby's needs. Such actions support children's social and emotional development, which, in turn, strengthens their cognitive development, the researchers write. These children are more likely to be resilient to poverty, family instability, parental stress and depression. Additionally, if boys growing up in poverty have strong parental attachments, they are two and a half times less likely to display behavior problems at school.

The approximately 40 percent who lack secure attachments, on the other hand, are more likely to have poorer language and behavior before entering school. This effect continues throughout the children's lives, and such children are more likely to leave school without further education, employment or training, the researchers write. Among children growing up in poverty, poor parental care and insecure attachment before age four strongly predicted a failure to complete school. Of the 40 percent who lack secure attachments, 25 percent avoid their parents when they are upset (because their parents are ignoring their needs), and 15 percent resist their parents because their parents cause them distress.

"This report clearly identifies the fundamental role secure attachment could have in narrowing that school readiness gap and improving children's life chances. More support from health visitors, children's centers and local authorities in helping parents improve how they bond with young children could play a role in narrowing the education gap," said Conor Ryan, director of research at the Sutton Trust.

Susan Campbell, a professor of psychology at the University of Pittsburgh who studies social and emotional development in young children and infants, said insecure attachments emerge when primary caregivers are not "tuned in" to their infant's social signals, especially their cries of distress during infancy.

"When helpless infants learn early that their cries will be responded to, they also learn that their needs will be met, and they are likely to form a secure attachment to their parents," Campbell said. "However, when caregivers are overwhelmed because of their own difficulties, infants are more likely to learn that the world is not a safe place — leading them to become needy, frustrated, withdrawn or disorganized."

The researchers argue that many parents — including middle-class parents — need more support to provide proper parenting, including family leave, home visits and income supports.

"Targeted interventions can also be highly effective in helping parents develop the behaviors that foster secure attachment. Supporting families who are at risk for poor parenting ideally starts early — at birth or even before," said Waldfogel, a co-author of the report and a professor of social work and public affairs at Columbia.