Much has been made of Dr Zucker's claimed success in taking a genitally injured 2 month old boy and turning him into an ultra-butch bisexual chronically depressed person. A "success" because she absolutely definitely identifies as female, no question, uh huh. Of course, she used to *think* she was a boy, when she was young, but it was made quite clear to her by her parents and everyone else that that was UNACCEPTABLE. They took her preferred toys away, and punished her for saying that. Punished her again and again and again, year after year, until she complied with their wishes, gladly, willingly, even eagerly. She's not a boy, no siree, absolutely not. She's glad to be a girl. Really.

Please look at the details of that case. And all the other cases of Dr Zucker's "successes". He averages about 1 in 3. Most of whom even reach age 30.

I'll quote the abstract of a paper given at the APA annual meeting:

Title of Presentation: Brain Gender Identity

Abstract:

Gender Identity is that innate sense of who you are in this world with reference to your sexuality and behavior, not necessarily corresponding to your genitalia and reproductive organs. Transgenders are atypical and “think” as the opposite gender. Certain areas of the brain have been shown to be sexually dimorphic. They are different in structure and numbers of neurons in males versus females. Protein Receptors for the sex hormones in different areas of the brain (limbic and anterior hypothalamic) must be present in sufficient numbers to receive those powerful hormones. There are androgen receptors (AR), Estrogen Receptors (ER), and Progesterone receptors (PRs). ARs or ERs are predominant at different times in different parts of the human brain. Hormone receptor genes have been identified in humans, which are responsible for sexually dimorphic brain differentiation in the hypothalamus. The groundwork in brain gender identity is gene-directed and takes place by forming male and female hormone receptors in the brain before the gonads and hormones can influence them. Multiple genes acting in concert determine our sexual identity. The human brain continues to make neurons and synaptic neuronal connections throughout life. This contributes to Gender Role Behaviors making individuals in the continuum of gender identity. Gender behaviors must be differentiated from gender identity (Hines). Gender Identity cannot be predicted from anatomy (Reiner). Brain gender identity is determined very early in fetal development, but gender expression, expressed as behaviors requires hormonal, environmental, social and cultural interactions, which evolve with time. One cannot deny the profound effects of Testosterone, Estradiol and other steroids on genital differentiation in-utero or their effects on behavior from birth or the physical and mental cross gender changes caused by exogenous hormones, but gender identity is determined before and persists in spite of these effects.

Fortunately, a number of people will be both incompletely masculinised and incompletely feminised - so although not exactly a "blank slate", they can at least operate with some facility as either gender, if arbitrarily assigned one. Zucker really does have some successes. But most can't. Hence David Reimer, etc.