Four-year-old Shaun gets very upset when his older brother receives more cookies than he does at snack time. His older brother is typically given four cookies, while Shaun is only given two. To solve this problem, Shaun's dad breaks his two cookies in half before serving them. Shaun is then perfectly content as he believes he is receiving the same amount as his brother. According to Piaget, which concept has Shaun failed to grasp?
