Attachment theory began in the 1950s with the work of John Bowlby and Mary Ainsworth. Bowlby, an English psychiatrist, became interested in young children's responses to loss, and began studying the realms of attachment and bonding. He and Ainsworth, an American psychologist who conducted some of the most extensive field research into mother-infant interaction ever completed, formulated what is now commonly known as attachment theory.
Attachment theory is based on the belief that the mother-child bond is the essential and primary force in infant development, and thus forms the basis of coping, negotiation of relationships, and personality development. If the mother is absent or unavailable, a primary caregiver serves the mother's role. Attachment can be defined in both behavioral and emotional terms. From a behavioral perspective, attachment is represented by a cluster of instinctive child behaviors that serve to create the attachment bond, protect the child from fear and harm, and assist in the safe exploration of the world. These behaviors include reaching, clinging, sucking, and locomotion, and all facilitate maximum physical and emotional development.