So far, we have seen that there is a link between the quality of infant attachment and the quality of care an infant receives during the first year of life. Although interesting, this research would be less important if the effects applied only to the first year. They do not. Alan Sroufe, a psychologist at the University of Minnesota, and his colleagues continue to report on a longitudinal study of a large group of low-income families who were originally recruited in Minneapolis in the early 1970s (Sroufe, Egeland, Carlson, & Collins, 2005). Researchers observed these families' infants with their mothers in the Strange Situation when the infants were 12 and 18 months of age, and they then collected information on these children as they grew older. During the preschool years, teachers and observers rated children who had been securely attached as infants as happier and more socially skilled, competent, compliant, and empathetic than children who were insecurely attached as infants. Preschoolers with secure attachments also were more popular with their peers, had higher self-esteem, and were less dependent and negative.

By age 10 years, children in the securely attached classification were still less dependent and received higher ratings on self-esteem, self-confidence, social skills, and emotional health. They made more friends than did children who had been insecurely attached as infants, and they spent more time with their friends.

Adolescents who had been securely attached were more likely to be leaders in their social groups, they had longer-lasting dating relationships, and in early adulthood they reported greater satisfaction in their romantic relationships. The secure attachment they experienced with their parents had evidently carried through to their relationships with peers in childhood and with romantic partners later in life. Adolescents and adults who had insecure attachments as infants with their parents, however, had more emotional and psychological problems including anxiety disorders and depression.

How do these long-term attachment effects work? According to Sroufe, infants and children internalize the significant relationships that they have early in life, and use those early experiences as interpretive filters when they develop later relationships. People come to expect others to interact with them in a way that mirrors their early attachment relationships. Securely attached infants, therefore, grow up to seek and expect others to be supportive and positive—and they behave in ways that elicit these qualities in people around them. Insecurely attached infants, however, might later expect and provoke hostility, ambivalence, or rejection in their relationships.

Michael Lamb, a researcher at the National Institute of Child Health and Development, provides a different explanation (Lamb, 1987; Lamb, Thompson, Gardner, & Charnov, 1985). Lamb points out that parents who show sensitivity early on with their infants tend to be parents who remain warm and sensitive as their children grow older. Warm parenting during these later childhood years might be more important than first-year attachment in helping children to maintain positive behavioral, social, and personality characteristics. When parenting remains warm and supportive, we see secure attachments in infancy and correlations with positive characteristics later in the child's life. When the parenting and family circumstances change, however, these correlations can be disrupted. For example, divorce, illness and other negative circumstances can disrupt relationships even when children were securely attached as infants. And conversely, insecurely attached infants can benefit from later improvements in the quality of their care. Although the quality of the initial attachment is important in getting the infant off to a good start, it is clear that the quality and consistency of parental care after infancy also plays an important role (Thompson, 2006).