I. INTRODUCTION

Thedevelopment of the infant’s enduring emotional bond to the primary caregiver and the consequences of the nature of this bond have been the subjects of clinical and scientific interest for over a century. In a departure from the extant psychoanalytic and social-learning theories of his day, Bowlby (1969/1982) focused on the biological, evolutionary, and psychological bases of the child’s tie to the mother, thereby changing the course of scientific thinking about early social-emotional development. In the ensuing decades, Bowlby’s theory of attachment has inspired voluminous empirical work, synthesis, and revision (see Cassidy & Shaver, 2008), becoming one of the most well-established and well-validated theories in developmental science. In addition to focusing on universal attachment processes, Bowlby called attention to individual differences in the quality of attachment—secure or insecure—as well as the sources of these individual differences and their developmental consequences. Specifically, a central tenet of attachment theory (Bowlby, 1969/1982) is that the quality of early caregiving experiences (i.e., parental sensitivity and availability) forms the basis for the child to develop a relatively secure or insecure specific attachment to the caregiver, which generalizes to an internal representation of attachment that guides future relationships and social-emotional development. These ideas received empirical support and elaboration from Ainsworth, Blehar, Waters, and Wall (1978), who inspired a great deal of research in the infancy period and beyond. Although a life-span perspective was a fundamental aspect of Bowlby’s work, much of the initial (and current) research based on his theory has focused on the predictors and sequelae of the early mother–child attachment relationship (see Cassidy & Shaver, 2008). This is perhaps not surprising given the centrality of the infancy and early childhood period in attachment theory, as well as the relatively early development and validation of a laboratory-based