Babies Can Predict Trajectories

1. If you show very young babies a video of a static Big Bird that then explodes into its separately defined parts, they won't be perturbed. Because all the parts had separate edges anyway, they may, for all the babies know. have been separate objects to begin with. But if you show them Big Bird moving first, so that they see that all the parts of the object move together, and then show them the exploding Big Bird, they'll look much longer and more attentively, as if they recognize that something is wrong. Seeing the parts move together, seeing their common fate, seems to tell the babies that this is just one object and that its parts are eternally joined together. So babies already have some principles they can use to impose order on a chaotic world.

Movement seems to be important for babies in other ways, too. Very young babies already know a surprising amount about how objects characteristically move. Young babies not only can follow the movements of an object in front of them, they seem to be able to predict how an object will move in the future. Suppose you show the babies an object following a particular trajectory—that is, moving in a particular path at a particular speed—say, a ball rolling on the table. Now the ball rolls behind a screen. They will look ahead to the far edge of the screen, to the place where the object ought to appear if it keeps moving at the same rate and on the same path. If the object does appear there, the babies are unperturbed and keep following the object. But if the object doesn't appear there, or if it appears at the wrong spot or too quickly or too slowly, they look intently at the edge of the screen for much longer. Sometimes, in fact, they look back to the other edge of the screen, or look farther ahead along the path the object should have taken. They seem able to predict where the object should be and when it should get there.

If an object moving at a trajectory disappears behind a screen, the baby will look longer at the other end of the screen if it does not reappear at the proper time and place.