Stages of life/development: \n 1.) sensorimotor (birth-2): learn by exploration of immediate environment (mouth, eyes, hands, nose) \n 2.) preoperational (2-7): reconstruct concepts by grouping and naming (signs and signals) \n 3.) concrete operational (7-11): thinking logically, recognize size, length and weight, reasoning skills and deal with clock, calendar and geographical info, cause and effect \n 4.) formal operational (11-early adult): logical propositions, interpret space, historical time and multiple cause and effect relationships, plans of action, scientific method, complex math, linguistic and mechanical processes