Developmental psychology
Attachment theory, originally developed by John Bowlby, focuses on the importance of open, intimate, emotionally meaningful relationships. Attachment is described as a biological system or powerful survival impulse that evolved to ensure the survival of the infant. A child who is threatened or stressed will move toward caregivers who create a sense of physical, emotional and psychological safety for the individual. Attachment feeds on body contact and familiarity. Later Mary Ainsworth developed the Strange Situation protocol and the concept of the secure base.
Object relations theory
Attachment theory, researched by John Bowlby and others, has continued to deepen our understanding of early object relationships. While a different strain of psychoanalytic theory and research, the findings in attachment studies have continued to support the validity of the developmental progressions described in object relations. Recent decades in developmental psychological research, for example on the onset of a "theory of mind" in children, has suggested that the formation of the mental world is enabled by the infant-parent interpersonal interaction which was the main thesis of British object-relations tradition (e.g. Fairbairn, 1952).