What do two-year-olds understand about hidden-object events?

Preferential-looking studies suggest that by 2 months of age, infants may have knowledge about some object properties, such as solidity. Manual search studies of toddlers examining these same concepts, however, have failed to provide evidence for the same understanding. Investigators have recently attempted to reconcile this disparity but failed to control for the visual novelty of test outcomes. The current design corrected this problem and also tested toddlers' predictions of the object's location. The task involved the same events and apparatus that have been used in manual search tasks but used looking as the dependent measure. Children looked longer when an agent opened the correct door and found no ball than when an incorrect door was opened to reveal no ball. A 2nd experiment indicated that children's preferential-looking performance did not differ from that in manual search tasks simply because additional response time had been allowed to respond. Previous comparisons of looking versus reaching tested children's postdiction response to an object in an unexpected location, but these findings indicate that toddlers can predict where the object should be.