Final answer:
Mary Ainsworth identified different types of parent-child attachments and found that secure attachment is the healthiest.
Step-by-step explanation:
Mary Ainsworth conducted research on attachment and found that children differ in the ways they bond with their primary caregiver. She used the Strange Situation procedure to study attachment, where the infant and caregiver are placed in a room together and the caregiver leaves the room for a short period of time. Based on how the infants/toddlers responded to the separation and reunion, Ainsworth identified three types of parent-child attachments: secure, avoidant, and resistant. Secure attachment is considered the healthiest, where the child prefers the parent over a stranger, uses the parent as a secure base, and seeks comfort from the parent in times of stress.