Psychology regards the start of adulthood as the period after adolescence and spanning the rest of life. While not solely based on age, adulthood must also be characterized by achieving specific milestones of development such as independence, stable interpersonal attachments, taking on occupational tasks, and the fulfillment of personal identity. Traditionally, adulthood is viewed as comprising three segments. Early adulthood, which spans the ages of 20 to 40, is characterized by career development, the formation of intimate relationships, and family life. Middle adulthood, which spans the ages of 40 to 60, is characterized by the simultaneous fulfillment of occupational and family responsibilities and the onset of physical and cognitive aging. Late adulthood, which begins at age 60, is characterized by retirement, life review, and health decline as well as the loss of significant others. Psychologists such as Erik Erikson put great importance on middle adulthood as the time when the persons become psychosocially tasked with generatively and the physiologically responsible for decline. In more contemporary discussions, adulthood is characterized as a period of increasing cultural, social, and personal complexity. In more conservative cultures, adulthood is reached at the time of marriage, whereas in more permissive cultures, adulthood is reached and signified by a measure of financial independence. The modern view proposes that identity, interpersonal relationships, and life purpose continue to develop within growing psychosocial complexity that spans a lifetime.