Attachment theory proposes that secure attachment to caregivers in infancy and early childhood is crucial for healthy social-emotional development. Research on institutionalization and deprivation found that lack of consistent caregiving can impair children's ability to form attachments and relate to others. Studies of daycare quality suggest that high-quality care with low child-to-staff ratios, consistent caregivers, and social stimulation can support children's peer relationships and development, while poor quality care with frequent changes in caregivers or more than 20 hours per week may increase behavioral issues.