Attachment and Health
John Bowlby and Mary Ainsworth developed attachment theory in the 1960s while investigating the effects of maternal separation on infant development. The development of the Strange Situation task in 1965 by Ainsworth and Wittig allowed researchers to systematically investigate the attachment system operating between children and their parents. The Strange Situation involves separating infant-parent dyads and observing infant behaviours upon reunion. Infant behaviour tended to follow patterns, leading to the development of three attachment categories: Secure, Anxious-Avoidant, and Anxious-Resistant. In 1990, Ainsworth added a new category, championed by Mary Main, called Disorganized/Disoriented attachment, characterized by its less reliable pattern of behaviour.
Marinus van IJzendoorn
Van IJzendoorn's main research topic is attachment across the life-span. Attachment has been briefly defined as children's "strong disposition to seek proximity to and contact with a specific figure and to do so in certain situations, notably when they are frightened, tired or ill". Inspired by Darwinian evolutionary theory and Harlow's experimental work with rhesus monkeys, John Bowlby was the first to propose that human genetic selection had favoured attachment behaviours since they increased infant-parent proximity, which in turn enhanced the chances for infant survival. Attachment is considered to be an inborn capacity of every exemplar of the human species. Individual differences in the quality of attachment emerge in the first years of life, and central to attachment theory is the idea that parenting, more specifically parental sensitive responsiveness to the infant's distress signals, determines whether children develop a secure or an insecure attachment relationship with their primary caregiver. Van IJzendoorn introduced in 1995 the quantitative model of the ‘transmission gap’ between parents’ attachments and their infants’ attachment as mediated by parental sensitive responsiveness. This model generated a host of empirical studies trying to bridge the gap (see for a meta-analysis of this work).