The next phase, concrete operations, from seven to twelve, you can solve the conservation problem, but still you're limited to the extent you're capable of abstract reasoning.

下一阶段,具体运算阶段,七到十二岁,儿童可以解决守恒问题,但儿童的抽象推理能力仍然有限

耶鲁公开课 - 心理学导论课程节选