Dr. Lillard is an elected Fellow of the American Association for the Advancement of Science, the American Psychological Association (Division 7), and the Association for Psychological Science. She obtained her BA in English Literature from Smith College and her PhD in Psychology from Stanford University, where she worked with John Flavell.

Her primary research interests include Montessori education and children's play. She is currently chief Editor of Frontiers in Developmental Psychology. Her book, Montessori: The Science Behind the Genius is in its third edition and translated into several languages; it received the Cognitive Development Society Book Award.