By our way of thinking, the ability to form conceptualizations, a basic form of cognitive ability, must appear before language can appear. Piaget's work (cf., Flavell, 1963; Beard, 1969) provides the best ideas on the acquisition of this ability. He views the infant at birth as having only a few reflexes (such as sucking and grasping) and innate tendencies to exercise the reflexes and to organize their actions. The first evidence of the capacity to organize input appears in the development of habitual actions or responses. Well-defined, repeated sequences of actions Piaget calls action schema or schemata. Action schema is characteristic of the first stage of cognitive development, the sensori-motor stage. Later, the child begins to use symbols and becomes able to develop mental schemata.
After a schema has developed, it is applied to new objects and experiences. This process of incorporating new objects or experiences into existing schemata is called assimilation. The complementary process of modifying schemata to solve problems arising from new experiences or objects is called accommodation. Through the interplay of these two processes, the child assimilates new experiences into existing schemata or accommodates his schemata, by extending or combining them, to meet new situations.
The result is that the infant adapts to his environment by developing a sufficient repertoire of schemata; that is, in Piaget's terms, he attains a level of equilibrium between his cognitive schemata and the environment. However, as the environment changes or as the child extends his range of activity, the equilibrium is disturbed; further development of the schemata or the creation of new ones is necessary to restore it. The processes of assimilation and accommodation continue to result in more schemata that are better adapted to the environment, and the child continues to progress through the stages of cognitive development.