How we treat others in close relationships depends on our attachment style. Researchers in child development in the 1940s examined the emotional damage done to orphans and displaced children; out of that and further research in childhood development in the 1960s came the field now called attachment theory.
Children learn from their caregivers how to call for help and how to get their basic needs met through communication. A highly responsive caregiver who is good at understanding the child’s state and responding as needed tends to encourage in the child a trust of the caregiver and an attitude of safety in the world that encourages exploration and play, because the child feels secure—if he or she gets into trouble and cries out for help, the caregiver will come and save them. On the other hand, a child whose needs are ignored, or inconsistently met, or who is abused, develops a whole set of different adaptations to survive—some of which form the background assumptions to how they emotionally view the world of other people.
For a thorough discussion of the development and basics of adult attachment theory, read the Wikipedia entry Attachment in Adults and the seminal Hazan and Shaver paper.
What is Attachment Type?
In short, studies have shown that the styles of dealing with caregivers—those most important giants who we kept us safe and fed during childhood—tend to carry on in adulthood, and the basic templates adopted then are used to deal with anyone close—partners or friends. Knowing what templates we use, and the templates others use with us, can give us an intellectual understanding of communications issues that allows us to empathize with partners who are driving us crazy with their neediness, or hurting us with their coldness—it’s all in the signal-response dynamics of our attachment style. We will categorize a person by their predominant attachment style by referring to their attachment type.