Sociologists contend that the rules we follow, the language we speak, and the values we believe in have less to do with our DNA (nature) than with the cultural context into which we emerge (nurture). Socialization is the lifelong process through which people learn the attitudes, values, and behaviors appropriate for members of a particular culture.

Case studies, such as those of Isabelle and Genie, and primate studies support the importance of socialization in development. Conversely, twin studies have addressed the influence of hereditary factors on personality development.

The self is a distinct identity that sets us apart from others. It continues to develop and change throughout our lives. Sociologists Charles Horton Cooley, George Herbert Mead, and Erving Goffman have all furthered our understanding about development of the self. Cooley's looking-glass self results from how we present ourselves to others and how others evaluate us. Mead argued that there are two core components of the self: the I (our acting self) and the Me (our socialized self). Instrumental to Mead's view are significant others (individuals most important in development of the self). He described a three-stage process of self-development: the preparatory stage, the play stage, and the game stage. Mead used the term generalized other to refer to attitudes, viewpoints, and expectations of society as a whole that a child takes into account in his or her behavior. Goffman offered the dramaturgical approach, which studies interaction as if we are all actors on a stage. He suggested that many of our daily activities involve impression management—altering the self in order to create distinctive appearances and satisfy particular audiences—and face-work—the efforts people make to maintain a proper image and avoid public embarrassment.

Psychologists, such as Sigmund Freud, stressed the role of inborn drives in the development of the self. Child psychologist Jean Piaget identified four stages of personality development in his cognitive theory of development (sensorimotor, preoperational, concrete operational, and formal operational). Piaget viewed social interaction as key to development.

Lifelong socialization involves many different social forces and agents of socialization. Family is considered the most important of the socialization agents. Schools are another agent of socialization concerned with teaching students the values and customs of the larger society. Peer groups often serve as a transitional source to adulthood. The mass media have an impact on the socialization process that sociologists have also begun to consider. Workplaces can serve as socialization agents by teaching appropriate behavior within an occupational environment. Additionally, social scientists have increasingly recognized the importance of religion and the state as agents of socialization.

Rites of passage are symbolic representations of significant transitions that serve as a means of dramatizing and validating changes in a person's status. Such transitions mark stages of development in the life course. Sociologists who take a life course approach look closely at the social factors, including gender and income, that influence people throughout their lives, from birth to death. Two types of socialization occur as we journey through our lives: anticipatory socialization (the process of rehearsing for future roles), and resocialization (discarding former behavior patterns and accepting new ones). Resocialization is particularly effective when it occurs within a total institution, an institution that regulates all aspects of a person's life under a single authority. Goffman identified four common traits of total institutions. People often lose their individuality within total institutions, often by undergoing degradation ceremonies.

As we age, we move into the midlife transition, which typically begins at about age 40. Men and women often experience a stressful period of self-evaluation, commonly known as the midlife crisis. During the late 1990s, social scientists focused on the sandwich generation, or those adults who simultaneously try to meet the competing needs of their parents and their children. The experience of retirement varies according to gender, race, and ethnicity. Retirement is a series of adjustments that will differ for each individual, depending on such factors as financial and health status.