Developing an attachment to a principal caregiver (e.g., mother, father, other consistent caregiver) occurs during four developmental stages. During the first stage, from birth to about 10 weeks, the infant’s behavior is mostly reflexive. Newborns seek contact with and can be comforted by different people.

In stage 2, from 10 weeks to 6 months, infants develop social and cognitive abilities and can discriminate caregiver’s physical attributes. They also gain more control over their gross motor skills and can direct attachment behaviors (e.g., crying, clinging) toward consistent caregivers.

At approximately 6 to 7 months of age babies reach stage 3, in which a strong attachment to a specific caregiver is fully formed. Babies can crawl and soon walk, enabling them to seek out and maintain contact with their attachment figures when upset or in need of protection or comfort. Thus, they can communicate, attachment behaviors more actively, receive need-fulfilling responses from their caregivers, and create a strong, consistent, and reciprocal attachment relationship. This is a critical developmental milestone; these bonds are essential to subsequent key areas of development and will persist over the course of the lifespan. The fourth stage of attachment development begins around 30 months.

Young children have achieved more advanced social and cognitive capacities, and are learning to cope with separations and reunions in everyday life. For instance, they now understand that their caregiver will return after a few hours away, and do not experience the distress of an infant earlier in development. Young children feel more security at this time, and therefore, reduce contact- and proximity-seeking behavior of the younger infant (Marvin & Britner 2008).