So, for Piaget, the first stage is the sensorimotor stage or the sensorimotor period.

皮亚杰认为,第一个阶段,是感知运动阶段,或者说,感知运动期

耶鲁公开课 - 心理学导论课程节选

The child starts off grasping the world only in a physical way, in a sensorimotor way, but when he gets to the preoperational period, the capacity to represent the world, to have the world inside your head, comes into being.

开始的时候,儿童只能通过生理的方式,通过感知运动的方式,来认识世界,但是当儿童进入了前运算阶段,他们便逐渐拥有了表征事物,在头脑中构建世界的能力

耶鲁公开课 - 心理学导论课程节选