Terri, 4 months old, likes to learn about the shape and texture of a safe, soft rattle by sucking and chewing on it. By 9 months she is trying different ways to learn about the object.She shakes, bangs, switches hands, turns the rattle over to inspect the other side, tries to roll it and sit on it, and throws it many times, on y to r rieve it by crawling very quickly across the floor.This trajectory or path of development is continuous, as Terri seems to progress forward in her acquisition of skills that help her learn about objects such as rattles.