As a clinician evaluating young children who have developmental disabilities, Leavitt has been active in efforts to translate research into clinical practice.
At the Waisman Center, Leavitt directs an interdisciplinary training program for pre- and post-doctoral physicians, nurses and allied health professionals working in the field of developmental disabilities.
His work has used physiological measures, such as heart rate, skin conductance, and non-nutritive sucking, as well as behavioral observation.
His current work investigates the role of maternal sensitivity to infant signals in the development of mother-infant communication and behavioral interaction.
In 1972, he began working as a professor of pediatrics and head, Infant Processes Section at the Waisman Center on Mental Retardation and Human Development at the University of Wisconsin–Madison.