Final answer:
The healthiest attachment style identified by Mary Ainsworth, in which a toddler shows a preference for parents over strangers and uses parents as a secure base, is called secure attachment. This contrasts with avoidant, anxious-ambivalent, and disorganized attachment styles, each exhibiting different behaviors.
Step-by-step explanation:
Attachment Styles in Toddlers
According to research by Mary Ainsworth, the healthiest type of attachment style in which the toddler prefers his/her parents over strangers is called secure attachment. In this attachment style, the child uses the parent as a secure base to explore the environment and seeks comfort from the parent in times of stress. The securely attached children have caregivers who are sensitive and responsive to their needs. They show distress when separated from caregivers but are happy upon their return, indicating a stable emotional bond.
On the other hand, avoidant attachment is characterized by the child being unresponsive to the parent and not using the parent as a secure base. The anxious-ambivalent attachment involves children displaying clingy behavior yet rejecting interaction attempts, and they do not readily explore their environment. Finally, disorganized attachment is often seen in children who have been abused and show erratic or freezing behavior upon the caregiver's return.