Nature versus nurture
Certain characteristics may be innate in humans; these characteristics may be modified by the physical and social environment in which people interact. Human sexuality is driven by genetics and mental activity. The sexual drive affects the development of personal identity and social activities. An individual's normative, social, cultural, educational, and environmental characteristics moderate the sexual drive. Two well-known schools in psychology took opposing positions in the nature-versus-nurture debate: the Psychoanalytic school led by Sigmund Freud and the Behaviorist school which traces its origins to John Locke.
Freud believed sexual drives are instinctive. He was a firm supporter of the nature argument; he said there are a large number of instincts but they are reduced into two broad groups: Eros (the life instinct), which comprises the self-preserving and erotic instincts, and Thanatos (the death instinct), which comprises instincts invoking aggression, self-destruction, and cruelty. He gave sexual drives a centrality in human life, actions, and behaviors that had not been accepted before his proposal. His instinct theory said humans are driven from birth by the desire to acquire and enhance bodily pleasures, thus supporting the nature debate. Freud redefined the term sexuality to make it cover any form of pleasure that can be derived from the human body. He also said pleasure lowers tension while displeasure raises it, influencing the sexual drive in humans. His developmentalist perspective was governed by inner forces, especially biological drives and maturation, and his view that humans are biologically inclined to seek sexual gratification demonstrates the nature side of the debate. The nurture debate traces back to John Locke and his theory of the mind as a "tabula rasa" or blank slate. Later, behaviorists would apply this notion in support of the idea that the environment is where one develops one's sexual drives.
Psychological theories exist regarding the development and expression of gender differences in human sexuality. A number of them, including neo-analytic theories, sociobiological theories, social learning theory, social role theory, and script theory, agree in predicting that men should be more approving of casual sex (sex happening outside a stable, committed relationship such as marriage) and should also be more promiscuous (have a higher number of sexual partners) than women. These theories are mostly consistent with observed differences in males' and females' attitudes toward casual sex before marriage in the United States; other aspects of human sexuality, such as sexual satisfaction, incidence of oral sex, and attitudes toward homosexuality and masturbation, show little to no observed difference between males and females. Observed gender differences regarding the number of sexual partners are modest, with males tending to have slightly more than females.