Baillargeon's Violation-of-Expectation Infant Studies

Beginning in the mid-1980s the developmental psychologist Renee Baillargeon and colleagues published a series of studies using the violation-of-expectation paradigm to challenge Jean Piaget's claim that infants younger than about eight months lack any understanding that objects continue to exist when hidden from view. In the best-known of these studies, from 1985 and 1987, infants as young as three and a half to five months were shown a screen resembling a drawbridge rotating through a full one hundred eighty degrees, and were then shown either a physically possible event, in which the screen appeared to stop upon reaching a hidden box behind it, or a physically impossible event, in which the screen appeared to rotate straight through the space the box occupied. Relying on the well-established finding that infants look longer at events that surprise them, Baillargeon found that infants looked significantly longer at the impossible event than the possible one, indicating that they retained an expectation that the solid box continued to exist behind the screen and could not simply be passed through. The findings, since replicated with infants as young as three and a half months, suggested that a basic understanding of object permanence and the solidity of physical objects emerges considerably earlier in infancy than Piaget's original stage theory proposed.