Representing the existence and the location of hidden objects: Object permanence in 6- and 8-month-old infants

The present experiment investigated two facets of object permanence in young infants: the ability to represent the existence and the location of a hidden stationary object, and the ability to represent the existence and the trajectory of a hidden moving object. Six- and 8-month-old infants sat in front of a screen; to the left of the screen was an inclined ramp. The infants watched the following event: the screen was raised and lowered, and a toy car rolled down the ramp, passed behind the screen, and exited the apparatus to the right. After the infants habituated to this event, they saw two test events. These were identical to the habituation event, except that a box was placed behind the screen. In one event (possible event), the box stood in back of the car's tracks; in the other (impossible event), it stood on top of the tracks, blocking the car's path. Infants looked longer at the impossible than at the possible event, indicating that they were surprised to see the car reappear from behind the screen when the box stood in its path. A control experiment in which the box was placed in front (possible event) or on top (impossible event) of the car's tracks yielded similar results. Together, the results of these experiments suggest that infants understood that (1) the box continued to exist, in its same location, after it was occluded by the screen; (2) the car continued to exist, and pursued its trajectory, after it disappeared behind the screen; and (3) the car could not roll through the space occupied by the box. These results have implications for theory and research on the development of infants' knowledge about objects and infants' reasoning abilities.