Where's the rabbit? 5.5-month-old infants' representation of the height of a hidden object

Two experiments examined 5.5-month-old infants' ability to represent the height of a hidden object. The infants saw two test events in which a toy rabbit travelled along a horizontal track; the center of this track was hidden by a screen that had a large window in its upper half. The only difference between the two test events was in the height of the rabbit. In one event (possible event), the rabbit was shorter than the lower edge of the window; in the other (impossible event), the rabbit was taller than the window's lower edge. In both events, the rabbit travelled along the track, disappearing at one end of the screen and reappearing at the other, without appearing in the window. The infants looked reliably longer at the impossible than at the possible event, indicating that they (a) believed that the rabbit continued to exist and pursued its trajectory behind the screen; (b) represented the height of the rabbit behind the screen; and therefore (c) expected the tall rabbit to appear in the window and were surprised that it failed to do so. A control condition in which a pretest display suggested that two separate rabbits were used to produce the events (one travelling to the left and the other to the right of the screen) supported this interpretation. The results have implications for research on the development of infants' ability to represent and use information about the physical and spatial properties of hidden objects.