Horizontal and vertical décalage

Horizontal and vertical décalage are terms coined by developmental psychologist Jean Piaget, which he used to describe the four stages in Piaget's theory of cognitive development: sensorimotor, preoperational, concrete operations, and formal operations. According to Piaget, horizontal and vertical décalage generally occur during the concrete operations stage of development.

Horizontal décalage refers to fact that once a child learns a certain function, he or she does not have the capability to immediately apply the learned function to all problems. In other words, "a horizontal décalage arises when a cognitive structure that can be successfully applied to task X cannot, though it is composed of the same organization of logical operations, be extended to task Y." Horizontal décalage is frequently used in reference to a child's ability to solve different conservation tasks. This concept recognizes that an individual child will not necessarily be on the same level of functioning in all possible areas of performance. Rather, "concepts and schemas develop through operation on and manipulation of objects in a specific manner." Vertical décalage refers to a child using the same cognitive function in different stages across development. In this sense, a child is improving upon a certain cognitive function, such as seriation tasks, as he or she ages.