University of Alberta Dictionary of Cognitive Science: Adaptation

In Piaget's theory of development, there are two cognitive processes that are crucial for progressing from stage to stage: assimilation, accommodation. These two concepts are described below.

Assimilation

This refers to the way in which a child transforms new information so that it makes sense within their existing knowledge base. That is, a child tries to understand new knowledge in terms of their existing knowledge. For example, a baby who is given a new object may grasp or suck on that object in the same way that he or she grasped or sucked other objects.

Accommodation

This happens when a child changes his or her cognitive structure in an attempt to understand new information. For example, the child learns to grasp a new object in a different way, or learns that the new object should not be sucked. In that way, the child has adapted his or her way of thinking to a new experience.

Taken together, assimilation and accommodation make up adaptation, which refers to the child's ability to adapt to his or her environment.

References:

Siegler, R. (1991). Children's thinking. Englewood Cliffs, NJ: Prentice-Hall.
Vasta, R., Haith, M. M., & Miller, S. A. (1995). Child psychology: The modern science. New York, NY: Wiley.