During which of Piaget's stages does a child demonstrate the ability to reason about abstract ideas and novel information?

Formal Operational Stage

Explanation:

The formal stage of operation starts at about twelve years of age and lasts into adulthood.

As teenagers join this phase, they acquire the capacity to think abstractly by manipulating thoughts in their heads, without relying on tangible manipulation.

This theory was made popular by Inhelder & Piaget in 1958.