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Contemporary knowledge of infant cognition relies heavily on violation-of-expectation experiments. However, there are two ways to conceptualize what occurs in such studies. Babies may react to anomalous test events because of preexisting world knowledge. Alternatively, they may react because they have learned about events during the familiarization period. One way to distinguish these possibilities is to contrast familiarization with everyday versus anomalous events. In the studies we report here, we used this method to probe the nature of 5-month-olds' expectations about the locations of objects hidden in sand and later revealed. In Experiment 1, infants who initially saw everyday events did react to anomalous ones, as found previously, whereas infants who initially saw anomalous events did not react to everyday events. In Experiment 2, two alternative explanations of this pattern were ruled out. We conclude that by the age of 5 months, infants have expectations regarding the location of objects in continuous space.

Prior data have revealed striking contrasts between 18- and 24-month-old children in place learning, an ability known to depend on the hippocampus (Newcombe, Huttenlocher, Drummey, & Wiley, 1998). The current research examined the development of three other basic abilities of mature spatial competence: the representation of multiple locations, the learning of relations among objects, and the recall of a single location after a substantial filled delay. Results indicated a transition from 18 to 24 months in all three abilities. This evidence supports a general transition in spatial representation that occurs towards the end of infancy. Existing neurobehavioral data suggest that a corresponding change in hippocampal functioning underlies this development.