Final answer:
Mary Ainsworth researched the importance of attachment in early childhood social development using the Strange Situation procedure. She identified three types of attachments and found that secure attachment is the healthiest.
Step-by-step explanation:
Mary Ainsworth was a researcher who focused on studying the importance of attachment in early childhood social development. She conducted her research in 1970 using a procedure called the Strange Situation, which involved placing the mother and her infant in a room together and observing their interactions.
Based on how the infants/toddlers responded to the separation and reunion, Ainsworth identified three types of parent-child attachment: secure, avoidant, and resistant.
Secure attachment, which is considered the healthiest, involves the child preferring their parent over a stranger and seeking them out in times of stress.
Ainsworth's research has been supported by subsequent studies, but there has also been criticism about factors like a child's temperament and cultural variations in attachment.