A containment event tests the infant's recognition that an object that is bigger than a container cannot fit completely into that container. Elizabeth Spelke, one of the psychologists who founded the naïve physics movement, identified the continuity principle, which conveys an understanding that objects exist continuously in time and space. Both occlusion and containment experiments hinge on the continuity principle. In the experiment, the infant is shown a tall cylinder and a tall cylindrical container. The experimenter demonstrates that the tall cylinder fits into the tall container, and the infant is bored by the expected physical outcome. The experimenter then places the tall cylinder completely into a much shorter cylindrical container, and the impossible event confuses the infant. Extended attention demonstrates the infant's understanding that containers cannot hold objects that exceed them in height.