ABSTRACT
In the mid-1980s, the method of preferential looking, long a stand-by for studying infants' visual behavior, was adapted to answer questions about very young infants' conceptions of objects and events. A landmark study by Baillargeon, Spelke, and Wasserman (1985) challenged the long-held Piagetian notion that infants did not have object permanence until around 8 to 10 months of age. In contrast to Piaget's hidden object task, which involved removing a cloth and reaching for the object, the new procedure used looking longer to events inconsistent with physical laws. The new paradigm, dubbed "violation of expectation," was a welcome change in procedures because it could test infants before they began to reach. The authors reasoned that very young infants who are unable to search for objects because of motoric immaturity might have knowledge of hidden objects, but be unable to show it in a search task. In a series of studies following the original (for reviews, see Baillargeon, 1993; Spelke, 1991), the new looking-time task featured objects either stationary or undergoing motion out of sight behind a screen. When the screen was raised, the object was either in a position one would expect from physical constraints on the motion or another position that was inconsistent with physical constraints. By presenting infants with perceptual events that appeared to be possible (within the laws of physics) and impossible (violating physical laws), their data revealed that very young infants looked longer at impossible events.
