Others have suggested that the ability to perform deferred imitation appears earlier. There is evidence that 14 month olds can imitate the actions of live models as much as a week after seeing them. Object permanence is also a part of the sensorimotor stage. Object permanence is the idea that an object is permanently in the world, even if it is removed from view. Infants start out believing that objects placed out of sight are out of existence, and gradually acquire the belief that out of sight does not mean out of this world.
Infants start life as egocentrics, as they are unable to think of another person's point of view.
This egocentrism can explain why children may appear selfish, as they are unable to think of others viewpoint. The notion of egocentrism is related to the idea of whether children can think symbolically. Conservation is another notion that children must learn. Initially, they judge objects on their size rather than content, so changes in the shape of a container will affect their judgment of which is bigger rather than the actual volume. Related to the conservation idea, children also do not always distinguish between appearance and reality during this period.