According to the author of "Theories of Development," William Crain, no one has made a more substantial contribution to the psychoanalytic theory of development than psychologist, Erik Erikson. Erikson defined eight stages of life: oral, anal, phallic, latency, puberty, young adulthood, adulthood and old age.
The Oral Stage
From birth to around age one, the mouth serves as the primary zone through which babies take in things. The ego is developing in babies, who keenly observe visually stimulating things and absorb good feelings. Babies begin trusting their caretakers when they find predictability and consistency in their actions. Without consistency, babies will develop mistrust.
The Anal Stage
Between ages two and three, children can control their sphincter muscles and begin exercising their autonomy by holding on to things one moment and then pushing them aside in the next. Dr. Harvey Karp says that the right side of a toddler's brain is the emotional, impulsive and nonverbal side and so this should explain much of a toddler's erratic behaviour. Shame and doubt surface as parents try to toilet train their children and regulate their behaviour. Children become aware of societal expectations and pressures.
The Phallic Stage
Between ages three and six, children enter an Oedipal crisis whereby they develop a keen interest in the genital zone and envision themselves in adult roles competing with one parent for the other. The superego emerges to regulate social behaviour and the child learns how to self-regulate.
The Latency Stage
Around ages six to 11, children learn to master cognitive and social skills and sexual drives become dormant. Feelings of inadequacy and inferiority may plague children who did not resolve conflicts from earlier stages, especially in a classroom setting. Educators can help children at this time by making them feel competent.
In adolescence, Oedipal fantasies re-emerge and teenagers find themselves going through substantial physical and emotional changes. Identity becomes critical at this stage and teenagers seek out groups and friends with philosophies that they feel are in tune with their own.
If young adults have developed a sufficient sense of identity, they can normally pursue meaningful relationships in this stage. In adolescence, most teenagers are too focused on self and how others perceive them to explore meaningful relationships. Young adulthood is normally the stage at which individuals experience true intimacy.
In adulthood, individuals become preoccupied with raising the next generation through procreation or caring for the offspring of others. Parenting can reduce the self-absorption and stagnation that occurs in adulthood when people become too involved in work and their own lives to care for others.
In old age, individuals embark on a review of their life to answer the question of whether the life they've lived in the past was worth it and to confront their mortality. The elderly must often contend with the loss of friends, spouses, relatives, income and status. However, the opportunity for new experiences still exists, as evidenced by women like Josefina Villaverde, who, at age 101, launched her political career by running for office in Spain.