Object permanence and conservation differ in that conservation is mastered in which stage?

1. Both are landmark cognitive achievements but at different ages. 2. Object permanence is an infant achievement, cited as a sudden change. 3. Piaget's third stage is the concrete operational stage, from about 7 to 11 years old. 4. In this stage, children also master the concept of conservation. 5. Formal operational, from about 11 to adulthood, comes after conservation is already in place. _Source: OpenStax Psychology 2e (CC BY 4.0), Ch 9 'Lifespan Development', sections 9.1-9.4_