Attachment theory proposes that secure attachment to caregivers in infancy and early childhood is crucial for healthy social-emotional development. John Bowlby and Mary Ainsworth were influential researchers who developed and tested attachment theory. Bowlby proposed that infants have an innate need to form attachments, and that secure attachment provides a child with a safe base to explore from and comfort when distressed. Ainsworth identified patterns of secure, avoidant, resistant, and disorganized attachment based on a child's response to separation from and reunion with their caregiver. Insecure attachment can result from inconsistent or neglectful caregiving and is associated with later psychopathology. Attachment theory is important in understanding the development of relationships and mental health.