Infant sensitivity to shadow motions

Preferential looking experiments investigated 5- and 8-month-old infants' perception and understanding of the motions of a shadow that appeared to be cast by a ball upon a box. When all the surfaces within the display were stationary, infants looked reliably longer when the shadow moved than when the shadow was stationary, indicating that they detected the shadow and its motion. In further experiments, however, infants' looking was not consistent with a sensitivity to the shadow's natural motion: They looked longer at natural events in which the shadow moved with the ball or remained at rest under the moving box than at unnatural events in which the shadow moved with the box or remained at rest under the moving ball. These findings suggest that infants overextend to shadows a principle that applies to material objects: Objects move together if and only if they are in contact. In a final experiment, infants were habituated to a moving shadow that repeatedly violated one aspect of the contact principle. In a subsequent test they failed to infer that the shadow would violate another aspect of the contact principle. Instead, they appeared to suspend all predictions concerning the behavior of the shadow.