Answer:
The work she developed about the attachment relationship between the child and his mother figure.
Step-by-step explanation:
Mary Salter Ainsworth born in Glendale, Ohio in 1913, she earned her doctorate degree in Developmental Psychology from the University of Toronto in 1939.
She is a central figure in psychology because of the work she developed about the attachment relationship between the child and his mother figure. The main questions of her research were: how is this relationship characterized? How can you study? What is its importance in the development of the child's social behavior?
She also had contribtions in the study of emotional development.