<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> In Freudian psychology, psychosexual development is a central element of the psychoanalytic sexual drive theory, that human beings, from birth, possess an instinctual libido (sexual energy) that develops in five stages . Each stage--the oral, the anal, the phallic, the latent, and the genital--is characterized by the erogenous zone that is the source of the libidinal drive . Sigmund Freud proposed that if the child experienced sexual frustration in relation to any psychosexual developmental stage, he or she would experience anxiety that would persist into adulthood as a neurosis, a functional mental disorder . </P> <P> Sigmund Freud (1856--1939) observed that during the predictable stages of early childhood development, the child's behavior is oriented towards certain parts of his or her body, e.g. the mouth during breast - feeding, the anus during toilet - training . He argued that adult neurosis (functional mental disorder) often is rooted in childhood sexuality, and consequently suggested that neurotic adult behaviors are manifestations of childhood sexual fantasy and desire . That is because human beings are born "polymorphous perverse", infants can derive sexual pleasure from any part of their bodies, and that socialization directs the instinctual libidinal drives into adult heterosexuality . Given the predictable timeline of childhood behavior, he proposed "libido development" as a model of normal childhood sexual development, wherein the child progresses through five psychosexual stages--the oral; the anal; the phallic; the latent; and the genital--in which the source pleasure is in a different erogenous zone . </P>

Who called the stages of development psychosexual stages