Holden and his older sister, Rachel, are sitting together ea…

Holden and his older sister, Rachel, are sitting together eating pizza. Rachel gives herself two slices of pizza and one slice to Holden. Holden complains that he has less pizza than Rachel. Rachel reaches over, cuts Holden’s one slice of pizza in half, and says, “There, now you also have two slices!” This solution satisfies Holden. What stage of cognitive development is Holden most likely at?