Born in Quebec, Canada, Baillargeon is the third child of French-Canadian parents. She is best known for her research showing that infants have an intuitive awareness of physical laws such as solidity, containment, and occlusion at a young age. However, her research interests encompass a variety of issues in causal reasoning, focusing not only on the physical but also the psychological, sociomoral, and biological domains. Baillargeon received a B.A. in Psychology from McGill University in 1975 and a Ph.D. in Psychology from the University of Pennsylvania in 1981 under the supervision of Rochel Gelman and Elizabeth Spelke. Subsequently from 1981 to 1982, Baillargeon completed a postdoctoral fellowship at MIT under the supervision of Susan Carey. She received her first academic appointment at the University of Texas at Austin in 1982, a year later she moved to the University of Illinois where she has remained since.
Baillargeon's research on causal reasoning in infants furthered understanding concerning Piaget's theory of cognitive development. Piaget's experiments on the development of a concept of object permanence in infants required the children to manually search for the hidden object by pulling a cover off to reveal the object. Baillargeon argues that Piaget's finding regarding infants' failure to understand object permanence until 8–12 months old was rooted in a lack of motor ability as opposed to inadequate cognitive development. In an effort to account for infants' lack of motor skills, Baillargeon's studies of object permanence measure infants' fixation times on impossible versus possible events.
