Period I | Sensori-Motor Intelligence (birth to 2 years) Physical activities are organized around sucking, grasping, and hitting. |
Period II | Preoperational Thought (2 to 7 years) Individuals use symbols and internal images. Thinking is not systematic and not logical. Thinking is different from that of most adults. |
Period III | Concrete Operations (7 to 11 years) Individuals can think logically and systematically if linked to concrete objects and/or activities. |
Period IV | Formal Operations (11 to adulthood) Individuals can think logically and systematically. Individuals can think abstractly. |