| Stage | Age |
| Sensorimotor | Birth to 2 years |
| (sub-stages described in Chapter 2) | |
| Preoperational | 2 to 7 years |
| Concrete operations | 7 to 11 years |
| Formal operations | 11 years to adult |
Piaget introduced several terms and ideas into psychology that are still used today:
Adaption - the process of making adjustments to suit the environment
Schemata - mental concepts or categories
Assimilation - trying to fit new learning into existing schemata
Accommodation - changing existing schemata to incorporate new learning
Disequilibrium - disturbed mental balance that necessitates assimilation or accommodation
Other Piagetian concepts will be addressed in subsequent chapters.