John Bowlby was a psychiatrist in London in the early 1900s whose work with children experiencing separation from their mothers led him to believe that infants have a universal need to form attachments with caregivers to ensure survival. He argued that separation from mothers caused extreme distress in children and shaped their long-term development, contradicting previous theories. Bowlby's research introduced the idea that children are born pre-programmed to attach to a primary caregiver, usually the mother, for continuous care during the first two years of life to develop healthy emotional and social skills.