Attachment theory asserts that there is a biological imperative for infants to form attachments and that they exhibit attachment behaviours to promote attachment. These attachment behaviours - such as smiling, crying, following, approaching, clinging etc. - all serve to keep the child close to the carer. In this sense attachment behaviour can be viewed as survival behaviour, and similar behaviours can be observed in the young of other species.
Attachment theory relates the quality of early attachment relationships to emotional functioning throughout life. It also relates language, cognitive, and moral development to the quality of early attachment relationships. Humans do appear to have a basic propensity to form intimate emotional bonds. Bowlby (1969) argued that we have a biological need to seek and maintain contact with others. That we have an impulse to maintain closeness, to restore it if impaired, and to seek out a particular person if we are distressed. This process begins in infancy, but continues throughout life.