Four-year-olds are not completely egocentric and 5-year-olds can exhibit some understanding of conservation. This indicates that Piaget may have underestimated the:

Continuity of cognitive development

Explanation:

Hello! Cognitive development is the process by which man acquires knowledge through learning and experience. In this case, Piaget formulated that just at seven years old the reasoning ability is developed through logic in children. However, there are children who upgrade in these areas years before.