[2] 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.
[3] 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.
[6][7] 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.
A study by Baillargeon and colleague Julie DeVos confirmed the concept of object permanence in infants as young as 3.5 months old.
[9] Baillargeon uses the term "violation of expectation paradigm" to account for the surprise which infants show by gazing longer at an impossible event.