Mary Ainsworth

Mary Dinsmore Ainsworth (née Salter; December 1, 1913 – March 21, 1999) was an American-Canadian developmental psychologist known for her work in the development of the attachment theory. She designed the strange situation procedure to observe early emotional attachment between a child and their primary caregiver.

A 2002 Review of General Psychology survey ranked Ainsworth as the 97th most cited psychologist of the 20th century. Many of Ainsworth's studies are "cornerstones" of modern-day attachment theory.