Moving with the effects of gravity provides a practical ability to roll over. Caregivers need to position their arms and legs and push to start the roll. The person uses the information about moving to understand the direction and to continue rolling with the assistance of gravity. Understanding the effects of gravity also has the practical advantage of being able to hold still.
Moving with the effects of gravity is part of the enjoyment experienced while rocking.
Better trunk stability allows them to sit up longer than in ACL 1.4. While they are up they can engage in choosing sensory information. Their choices provide better opportunities to identify personal preferences and produce a sense of pleasure. With a sense of pleasure, it is easier to engage and sustain actions that maintain muscle strength, organ functions and the identity of the individual.