Child and Cockatoo (image) University of Vienna Share Print E-Mail Caption How do you know that something you cannot see is still present? Full object permanence including invisible trajectories through time and space takes years to develop in human infants. Credit Alice Auersperg Usage Restrictions The image may only be used with appropriate caption or credit. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.