Consistent with gelman's observations of piaget's conservation tasks, researcher have found that children who engage in private speech are more their task.

The term conservation denotes the fact that two things that are equal remain so if their appearance is altered, as long as nothing is added or taken away. Private speech is the use of language for self-regulation.
Consistent with Gelman's observations of Piaget's conservation tasks, researcher have found that children who engage in private speech are more focused on their task.

The one that most represents the earths mantle would be the skin since the mantle is the upper part of the earths depths which is just like the skin of an apple.