Sigmund Freud's theory of psychosexual development (1905)Freud's theory of development was based on the assumption that development is influenced by sexual drives. Freud proposed his theory of psychosexual development in his article “Three Essays on the Theory of Sexuality” originally published in 1905 and later translated into English in 1962. He theorized that from birth, human beings have an instinctive sexual energy (i.e. libido ) which is a significant component of personality development. Freud's theory of psychosexual development consists of five linear stages spanning the entire lifespan. Each of these phases is characterized by a specific erogenous zone which is at the center of the conflict of the evolutionary phase (Freud, 1962). Freud (1962) believed that the erogenous zones involved in development were the mouth, the anus and the genital region. The conflicts and behaviors in each of the psychosexual phases are closely associated with these erogenous areas. Because Freud's theory of development is linear, a child is unable to progress to the next stage – that is, he is unable to focus on the sexual energy associated with the primary erogenous zone of the next stage (Freud, 1962). The central conflict in the psychosexual stage must be resolved in order for an individual to move on to the next stage. According to Freud (1962), the positive resolution of each of these phases involves an expenditure of sexual energy. Freud (1962) theorized that more energy is used to overcome the conflict of a psychosexual stage leads to characteristics/traits/behaviors of that stage that last into adulthood. He believed that any enduring characteristic/trait/behavior is what could underlie personality and psychopathology in adulthood (Freud, 1962). According to Erikson (1950), individuals at this stage develop a sense of belonging to society. Individuals capable of contributing to society can develop a sense of generativity (i.e., a sense of productivity and accomplishment). In contrast, Erikson (1950) believed that individuals who are unwilling to contribute to society may develop a sense of stagnation. The eighth and final stage, integrity vs. despair, occurs in late adulthood. According to Erikson (1950) the main task of this stage is retrospection. individuals contemplate their own achievements. If individuals believe they have had a successful life, they develop a sense of integrity. Individuals may be more likely to develop feelings of hopelessness if their life is full of disappointments and unachieved goals (Erikson).)., 1950).