Final answer:
Mason's belief that there is more Silly Putty after it has been flattened indicates he has not mastered the concept of conservation, a key principle in Piaget's theory of cognitive development.
Step-by-step explanation:
Daryl's son, Mason, believes there is more Silly Putty after it has been flattened because he has not mastered the concept of conservation. Conservation is the understanding that altering the appearance of an object does not change its key properties, such as volume or mass. In Piaget's theory of cognitive development, the stage at which children begin to understand the concept of conservation is the concrete operational stage. Prior to reaching this stage, younger children are in the preoperational stage, during which they often judge quantities by their appearance rather than by true amounts. This type of scenario is similar to the classic conservation tasks developed by Piaget, where children are asked about the volume of liquid in differently shaped containers or the amount of clay when it's reshaped. Mason's response indicates that he is still in the preoperational stage of cognitive development.