Daniel Levinson's theory is the life structure. This is an underlying pattern of an individual's life at any given point in time. A person's life structure is shaped mainly by their social and physical environment, and it primarily involves family and work. There are 6 stages of adulthood in Levinson's theory: Early adult transition (17-22) leave adolescence, make preliminary choices for adult life (Berger, 2010). Entering the adult world (22-28) make initial choices in love, occupation, friendship, values, lifestyle (Berger, 2010). Age 30 transition (28-33) changes occur in life structure, either a moderate change or, more often, a severe and stressful crisis (Berger, 2010). Settling down (33-40) establish a niche in society, progress on a timetable, in both family and career accomplishments; are expected to think and behave like a parent creating roles and expectations (Berger, 2010). Mid-life transition (40-45) life structure comes into question, usually a time of crisis in the meaning, direction, and value of each person's life (Berger, 2010). Entering middle adulthood (45-50) choices must be made, a new life structure formed (Berger, 2010).
In addition, Abraham Maslow developed his theory based on a concept of a Hierarchy of Needs. According to Maslow, the hierarchy of needs consist of five needs which are physiological needs, safety needs, love needs, esteem needs, and self-actualization needs. In Maslow’s hierarchy of needs, all of the basic needs are at the bottom of the pyramid. The needs that are not most important are towards the top of the pyramid. Once the bottom set of needs are met or fulfilled, a person will move up to the next level of needs and so on and so on. An individual will always start off with the most basic set of needs called Physiological needs, and will not skip to another part of the pyramid without satisfying these needs and wants first (Berger, 2010).
Erik Erikson recognized several stages psychosocial child development that each individual goes through during his or her entire life span. In Erikson's theory, the stages of development process unfold as one goes through life. In early adulthood, "Intimacy versus Isolation” is a stage of life where the individual is searching for a mate and a home of her own (Berger, 2010). The progression is to "Generativity versus Stagnation." This stage has more societal control than any other, and these years are busy and creative. One may struggle with stagnation or self-absorption when the children leave home or if his career is not fulfilling (Berger, 2010). The final stage is “Integrity versus Despair." He believed that if a person was satisfied with the life he or she lived meaning then the declining years would be a time of contentment. A contented older adult may feel vindicated and wise, while discontented persons may feel despair as they focus on their failures. It is important to note that Erickson felt that is was not necessary bind stages to age groups and that stages could