Piaget defined a schema as the mental representation of an associated set of perceptions, ideas, and/or actions. Piaget considered schemata to be the basic building blocks of thinking (Woolfolk, 1987). As cognitive development proceeds, new schemata are developed, and existing schemata are more efficiently organised to better adapt to the environment. Cognitive development becomes evident through changes in behavior as this adaptation takes place. The process of assimilation involves attempts to organize existing schemata for better understanding events in .the external world, whereas accommodation involves changing pre-existing schemata to adapt to a new situation.
This illustration demonstrates a child developing a schema for a dog by assimilating information about the dog. The child then sees a cat, using accommodation compares existing knowledge of a dog to form a schema of a cat. Animation created by Daurice Grossniklaus and Bob Rodes (03/2002).