Reference: Developmental Psychology (1992), 28, 759-775. THE ORIGINS OF ATTACHMENT THEORY: JOHN BOWLBY AND MARY AINSWORTH INGE BRETHERTON Attachment theory is the joint work of John Bowlby and Mary Ainsworth (Ainsworth & Bowlby, 1991 ). Drawing on concepts from ethology, cybernetics, information processing, developmental psychology, and psychoanalysts, John Bowlby formulated the basic tenets of the theory. He thereby revolutionized our thinking about a child’s tie to the mother and its disruption through separation, deprivation, and bereavement. Mary Ainsworth’s innovative methodology not only made it possible to test some of Bowlby’s ideas empirically hut also helped expand the theory itself and is responsible for some of the new directions it is now taking. Ainsworth contributed the concept of the attachment figure as a secure base from which an infant can explore the world. In addition, she formulated the concept of maternal sensitivity to infant signals and its role in the development of infant-mother attachment patterns. The ideas now guiding attachment theory have a long developmental history. Although Bowlby and Ainsworth worked independently of each other during their early careers, both were influenced by Freud and other psychoanalytic thinkers-directly in Bowlby’s case, indirectly in Ainsworth’s. In this chapter, I document the origins of ideas that later became central to attachment theory. I then discuss the subsequent period of theory building and consolidation. Finally, I review some of the new directions in which the theory is currently developing and speculate on its future potential In taking this retrospective developmental approach to the origins of attachment theory, I am reminded of Freud’s (1920/1955) remark: I would like to thank Mary Ainsworth and Ursula Bowlby for helpful input on a draft of this article. I am also grateful for insightful comments by three very knowledgeable reviewers. Reference: Developmental Psychology (1992), 28, 759-775. Reprinted in from R. Parke, P. Ornstein, J. Reiser, & C. Zahn-Waxler (Eds.) (1994). A century of developmental psychology. (Chapter 15, pp. 431-471).