A psychiatrist has children complete tasks to assess development. each child is shown a three dimensional model of a mountain scene, while positioned on one side with the psychiatrist observing from the opposite side of the scene. The child is asked to look at four pictures from different viewpoints including both the child’s and the psychiatrist’s viewpoints. Nathan, one of the children from the group, looks at the 4 pictures and selects the viewpoint that matches his own. Which of piaget’s stages of cognitive development has nathan currently attained?