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.
Attachment parenting
In 1984, developmental psychologist Aletha Solter published her book "The Aware Baby" about a parenting philosophy that advocates attachment, extended breastfeeding and abstinence from punishment, similarly to what William Sears later wrote; however, the point that Solter stressed most was an encouragement of the child's emotional expression in order to heal stress and trauma.