sensorimotor stage

Meaning: In Piaget's theory, the sensorimotor stage runs from birth to about age 2. Infants learn by acting on the world through senses and movement: looking, grasping, sucking, shaking, dropping. Behavior begins as reflexes, then becomes repeated actions, first on the infant's own body and then on objects, and finally deliberate experimenting. By the end, the child can form mental representations, which leads into the preoperational stage. The central achievement is object permanence, the understanding that objects continue to exist when out of sight.

On the MCAT: A passage describes an infant who stops looking for a toy once it is covered, or who searches under a blanket for it. You identify the stage, or recognize that lacking object permanence means the child is early in this stage. Stage order is also tested: sensorimotor, preoperational, concrete operational, formal operational.

Common confusion: Object permanence is not present from the start, and it is not a preoperational skill. In Piaget's account it develops gradually during the sensorimotor stage. Symbolic thought, pretend play and egocentrism mark the preoperational stage. Later research suggests infants may show early signs of object permanence sooner than Piaget proposed, but the exam uses his timeline.