stages of cognitive development PIAGET

sensory motor stage ( 0-18 months)
develop simple motor responses( lack" object permanance" )
preoperaional stage( 18 months- 7 yrs)
develop "object permanance" and "representational though" ( lack conservation)
concrete operation stage( 7-11 yrs)
develop "conservation" and classification abilities improve
formal operations stage( 11-15 yrs)
begin to understand abstract ideas and hypothetical situations, capable of deductive reasoning