Deshandra and Desmond are sister and brother. Their mother has two equal balls of clay. She rolls one into a long, skinny snake and the other into a short, thick snake. Mom then asks the children which snake has the most clay in it. Desmond says the long, skinny snake. Deshandra says both snakes have the same amount of clay. Mom brings the baby, Martin, over and the children begin to play with him. Desmond takes Martin's blanket and hides it to see if Martin will find it. Martin thinks it has disappeared and begins to cry, so Desmond gives it back to him. Martin just turned six months old.

Which of Piaget's stages of cognitive development is Martin currently in?

ormal operational

concrete operational

sensorimotor

preoperational