The five stages of human development according to Freudian psychosexual theory are: oral, anal, phallic, latency and genital. This controversial theory was proposed by psychoanalyst Sigmund Freud to describe how personality develops in relation to the discovery of erogenous zones through a set of five distinct stages from early childhood into adolescence.
In the oral stage, the mouth is the main pleasure center. The instinctual tendency of young infants to suckle during this stage is described as a manifestation of the need to satisfy this pleasure center. Freud argued that denying children this suckling instinct was what led to the development of negative habits such as nail biting and thumb sucking.
During the anal stage, toddlers begin to experiment with a second erogenous zone that they become aware of, the anus. They learn to control their bodily functions and find pleasure in relief after being denied the need to use the toilet.
In the phallic stage, Freud proposed that preschoolers began to become aware of their genitals. During this stage, children discover the differences between themselves and the opposite sex, most commonly through their respective mothers and fathers. During this stage, the Oedipus and Electra conflicts can form in boys and girls respectively.
After these first three stages, the toddler goes into a stage of latency during which sexual instincts subside, and the conscience begins to form.
The final, genital stage involves the return of sexual impulses, leading to appropriate social behavior if the initial stages were successful or depraved sexual behavior if they were not.