If "Brain Sex" is controversial, the fourth attribute of Sexual Orientation is ever more so. Although there is public and political controversy, the overwhelming majority of medical and psychological practitioners agree that sexual orientation may prove to be mainly congenital, or at least firmly established in early childhood. The term "Sexual Orientation" is a bit misleading. It is more an erotic or love orientation in that Sexual Orientation determines the physical gender we find attractive, with whom we fall in love, and have romantic as well as sexual fantasies.
From experiments with animals, "experiments of nature" in humans, and genetic and neurological studies come a consistent, though still circumstantial, stream of evidence that indicates one's sexual orientation is largely hormonally determined by the presence of testosterone at key periods in fetal development, and possibly even beyond. As we have seen with congenital adrenal hyperplasia (CAH), female fetuses exposed to testosterone-like agents develop a 50/50 chance of a lesbian versus heterosexual orientation if raised as girls. Studies of identical twins also indicate that when one twin shows homosexual or lesbian expression, there is a 50/50 chance of homosexual or lesbian expression in the other twin—whether raised together or apart.
The remaining 50% of determination may be continued hormonal development, environmental considerations or a combination. One interesting consideration with determination may be during our early postnatal development since the fetal stage for human babies is not completed during gestation, but continues for a year or more outside the womb. And during this critical time after birth, we have the highest level of testosterone present, excluding the onset of puberty--with many brain receptors to receive this powerful hormone. At any rate, between the ages of three and six years, one's erotic orientation is established but may not be acted upon for decades, if at all.
The last of our five attributes, Gender Identity, is the last to be identified, and the least understood and researched. When one's Gender Identity does not match their Physical Gender, the individual is termed Gender Dysphoric. Like Sexual Orientation, gender dysphoria is not pathological in itself, but a natural aberration occurring within the population. As with sexual orientation, the percentage of the population having gender dysphoria is in dispute, with estimates ranging between one in 39,000 individuals to three percent of the general population.
Although it is useful for psychotherapists and other behavioral scientists to use diagnostic nomenclature in order to describe an individual, we must remember that these categories are often fluid. An individual may see and express themselves for years as a crossdresser, then change their self-identity to a more transgendered or transsexual one. This change may be because the individual actually changes their self-view with age, or more information and experience lead to a clearer understanding of self.
Gender dysphoric individuals commonly, even frequently, have a sexual orientation markedly different from their gender identity, which suggests that the key periods of these formations occur at differing times. While gender dysphoric individuals display a wide gamut of incongruity and discomfort with their physical gender, three main groups have been delineated:
Those individuals with a desire to wear the clothing of the other sex are termed crossdressers. Most crossdressers are heterosexual men--one's sexual preference has nothing to do with crossdressing. Many men like to wear women's clothing in private or in public, and may even occasionally fantasize about becoming a woman. Once referred to as a transvestite, crossdresser has become the term of choice.
Transgenderists are men and women who prefer to steer away from gender role extremes and perfect an androgynous presentation of gender. They incorporate elements of both masculinity and femininity into their appearance. They may be seen by some persons as male, and by others as female. They may live part of their life as a man, and part as a woman, or they may live entirely in their new gender role but without plans for genital surgery.
Men and women whose gender identity more closely matches the other sex are termed transsexual. These individuals desire to rid themselves of their primary and secondary sexual characteristics and live as members of the other sex. Hormonal and surgical techniques make this possible, but it is a difficult, disruptive, and costly process, and must not be undertaken without psychological counseling, careful planning, and a realistic understanding of the likely outcome. Most transsexual people are born and first live as male.
Transsexuals are diagnostically divided into the sub-categories of Primary or Secondary. Primary transsexuals display an unrelenting and high degree of gender dysphoria, usually from an early age (four to six years of age). Secondary transsexuals usually come to a full realization of their condition in their twenties and thirties, and may not act on their feelings until they are much older. Typically, secondary transsexuals first go through phases that would be self-assessed as being a "crossdresser or transgenderist."
The outcomes of transsexuals vary greatly. There seems to be no significance in the outcome differences between primary and secondary transsexuals. Those who complete this gender reassignment process (the process of "transition") and have exercised due diligence throughout generally do very well for themselves and lead happy and fulfilling lives. Unfortunately, others who go through the process on a perfunctory basis may be unprepared to fully and comfortably assimilate into their new gender role. In conclusion, when we think of gender, we need to realize that many combinations in gender exist, and that they are all natural. Although most people are morphologically male or female, those who homogeneously fill all five gender categories as the same gender may be in the minority. The largest minority, but still a minority.