Final answer:
John Bowlby is the founder of attachment theory, which focuses on the emotional bond an infant forms with a caregiver, and the importance of a 'secure base' for healthy development.
Step-by-step explanation:
The founder of attachment theory is John Bowlby. Bowlby developed the concept of attachment as the affectional bond that an infant forms with the mother, which is crucial for the child's social and emotional development. He proposed the idea of a 'secure base' to describe a healthy attachment between parent and child, emphasizing the need for a caregiver to be responsive to the child's needs and to engage in mutually enjoyable interactions.
Attachment theory was further elaborated by Mary Ainsworth's research, who used the Strange Situation procedure to study attachment between mothers and infants, showing variations in how children bond. Erik Erikson, another important figure in developmental psychology, developed a theory of personality development that goes through eight stages over the course of one's life, integrating more social factors as compared to Freud's psychosexual stages.