Final answer:
Attachment theory, developed by John Bowlby, highlights the importance of a primary caregiver-infant bond for child development, and Mary Ainsworth expanded on this with her identification of different attachment styles through the Strange Situation procedure.
Step-by-step explanation:
John Bowlby, building upon the research of Harlow and others, developed attachment theory, emphasizing the necessity of a strong emotional bond between an infant and their primary caregiver for proper social and emotional development. Bowlby identified this bond as an affectional tie that persists throughout life, coined the term secure base, and highlighted the importance of responsive caregiving and mutually enjoyable interactions.
Attachment theory was further elaborated by Mary Ainsworth, who introduced variations in attachment through her research. Ainsworth employed the Strange Situation procedure to observe the attachment relationships between caregivers and infants 12 to 18 months old. This led to the identification of three main attachment styles: secure, avoidant, and resistant, with a fourth style, called disorganized attachment, added later. Secure attachment is considered the healthiest, characterized by children showing distress upon caregiver departure but happiness upon their return.
While subsequent research supported Ainsworth's findings, criticism arose regarding factors such as temperament, cultural differences, and the impact these have on attachment. Understanding the nuances of attachment is key to comprehending its role in lifelong psychosocial development and the different ways individuals experience connections.