For example, early on a child may call a cat a doggy too, and a bunny a doggie, and so on. Today we believe that the transitions between stages are more gradual than Piaget thought. BUT we still recognize his stages as important milestones.
Children explore and understand the world through their senses.
By 5 months old, the child begins to be surprised by unexpected events object permanence is developing. By 8 months, object permanence is full developed. They are developing schemas for familiar faces. If they react by touching their nose, then they realize that they are looking at themselves, and have the concept of the sense of self. A sense of self develops at the end of the sensorimotor stage.