Socialization: the lifelong social experience by which individuals develop their human potential and learn culture. Personality: a person"s fairly consistent patterns of thinking, feeling, and acting. The biological sciences: the role of nature; initially, europeans linked cultural differences to biology. The social sciences: the role of nurture; behaviourism holds that behaviour is not instinctive but learned. Isolation (being cut off from the social world) can cause permanent developmental damage. Six researchers have made lasting contributions to our understanding of human development: sigmund freud, jean piaget, lawrence kohlberg, carol gilligan, george herbert mead, erik h. erikson. Basic human needs: eros and thanatos as opposing forces. Id and superego are in constant states of conflict, with the ego balancing the two. Sociologists note freud"s contributions: internalization of social norms, childhood experiences have lasting effect. Preoperational stage: use of language and other symbols. Concrete operational stage: perception of causal connections in surroundings. Differed from freud, viewing the mind as active and creative.