1. Sensorimotor
   1. 0-2 years
   2. Differed imitation
      1. 18-24 months
   3. Goal directed activity
      1. 12-18 months
   4. Object performance
      1. 4-8 months
   5. Physical actions
      1. 0-2 years
   6. Use of reflexes
      1. 0-2 months
   7. Co-ordination of reflexes
      1. 1-4 months
2. Preoperational
   1. Egocentrism
   2. Centration
   3. 2-7 years
   4. Mental activity
   5. Language
   6. Social and communicative
3. Concrete operational
   1. Conversation
   2. 7-12 years
   3. Applys logic
   4. Decentre
      1. Consider more than one dimension
   5. Reversibility
      1. Able to reverse transformation
   6. Recognize ascending and descending order
      1. According to size
4. Formal operational
   1. Think abstractly
   2. Hypothetical reasoning
   3. 12-15 years
   4. Reflective abstraction
   5. Own identity/social relationships
   6. Develops hypothes
   7. Inductive and deductive reasoning
   8. Systematic approach