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Innate bisexuality (or predisposition to bisexuality) is a term introduced by Sigmund Freud (based on work by his associate Wilhelm Fliess), that expounds all humans are born bisexual but through psychological development (which includes both external and internal factors) most become monosexual while the bisexuality remains in a latent state.
There is no modern scientific consensus as to how biology influences sexual orientation (see biology and sexual orientation).
 Three Contributions to the Theory of Sex
In his Three Contributions to the Theory of Sex (1920), Freud discusses the concept of inversion (i.e. homosexuality) with respect to its innateness, or the biological predisposition to homosexuality or bisexuality.
The conclusions that he draws are based on the fact that at early stages of development, humans undergo a period of hermaphrodism. Based on this, he asserts that, "the conception which we gather from this long known anatomical fact is the original predisposition to bisexuality, which in the course of development has changed to monosexuality, leaving slight remnants of the stunted sex."
This develops into a general theory that attraction to both sexes is possible, but that one is more common for each sex. He explains the inversion of homosexual attraction as the result of a traumatic episode or episodes that prevent the normal development of an attraction for the opposite sex.
Freud famously characterized humans as naturally "polymorphously perverse," meaning either that practically any object can be a source of erotic fulfillment, or that babies are relatively indifferent to the object of erotic fulfillment.
 Different usages
Many modern uses of the term innate bisexuality are more indicative of Alfred Kinsey's research than Freud's. In this sense, it is a suggestion that most or all human beings are functionally bisexual to some degree, but may not express that bisexuality as behavior.
Both theories have a great deal of controversy surrounding them, so it is particularly important to be aware of which is being discussed.
"Dora" was Ida Bauer (1882-1945), a patient of Freud's. He used the pseudonym Dora when writing about their sessions. Often the theory of innate bisexuality is discussed in association with Freud's sessions with Dora.
 Wolf Man
Another study often associated with this theory is that of the "Wolf Man", a patient who tried to repress his homosexual tendencies. Freud explained the Wolf Man's development in terms of an inability to repress his innate feminine nature.
 See also
- Three Contributions to the Theory of Sex by Sigmund Freud
- Dream Psychology by Sigmund Freud
- Three Commentaries on Gender in Freud's Thought: A Prologue to the Psychoanalytic Theory of Sexuality William I. Grossman, M.D, Donald M. Kaplan, Ph.D.