6 sub stages- refelcive schemes ( birth-1month, use innate reflexes to explore, building blocks), primary circular reactions (1-4months, shift in voluntary control of behaviour, degree of coordinationof senses and motor), secondary circular reactions (4-10months, become more aware of external world, begin tp intentionally act on thier enviornment), coordination of secondary schemes (10-12months, deliberately combine schemes to achive specific goal), tertiary circular reactions (12-18months, walking), beginning of thought (18-24months, form enduring mental representations, deffered imitation